Previous What's New in Cosmology's

Herschel out of Helium

29 April 2013 - The European Space Agency's Herschel Space Observatory has run out of liquid helium coolant, nearly 4 years after its launch. This means that there are currently no space infrared telescopes operating at wavelengths longer than the 4.5 μm channel of the Spitzer Space Telescope.

First Cosmology Results from Planck

31 March 2013 - Planck released its first cosmology results today. Technical preprints are available here. The 6 parameter Λ CDM model is an excellent fit to the Planck data, and also to the Planck plus ACT, SPT and WMAP polarization extended CMB data, and to the CMB plus supernovae, Hubble constant and baryon acoustic oscillation data.

The parameters of the 6-parameter ΛCDM model fit to Planck+WMAP polarization+SPT+ACT+BAO are ΩΛ = 0.692 ± 0.010; the baryon density = 0.416 ± 0.0045 yoctograms per cubic meter; the cold dark matter density = 2.23 ± 0.032 yoctograms per cubic meter; CDM:baryon density ratio = 5.36 ± 0.10; dark energy density = 3352 ± 125 eV/cc; H0 = 67.80 ± 0.77 km/sec/Mpc; and the age of the Universe = 13.798 ± 0.037 Gyr. The baryon density is known to 1.1% precision and the cold dark matter density is known to 1.4% precision.

The dark energy density is known to 3.7% precision. For theorists who set hbar and c to 1, it works out to (2.25 meV)4. We still have no good theory to explain this value.

Limits on 1 parameter extension to the 6 parameter model are

Planck data is available at the InfraRed Science Archive (IRSA).

Not the Mayan Apocalypse - WMAP 9 Year Data Released

21 Dec 2012 - Bennett et al. presents the basic results, while Hinshaw et al. presents the cosmological fits. The 6 parameter Λ CDM model is still an excellent fit to the WMAP data, and also to the WMAP plus ACT and SPT extended CMB data, and to the CMB plus supernovae, Hubble constant and baryon acoustic oscillation data. The data are available now at LAMBDA. This is the last version of WMAP results. The baton is now passed on to Europe's Planck.

The parameters of the 6-parameter ΛCDM model fit to WMAP+BAO+H0 are ΩΛ = 0.712 ± 0.010; the baryon density = 0.426 ± 0.008 yoctograms per cubic meter; the cold dark matter density = 2.17 ± 0.04 yoctograms per cubic meter; CDM:baryon density ratio = 5.11 ± 0.14; dark energy density = 3607 ± 144 eV/cc; H0 = 69.33 ± 0.88 km/sec/Mpc; and the age of the Universe = 13.75 ± 0.085 Gyr. Both the baryon density and the cold dark matter density are known to 2% precision.

The dark energy density is known to 4% precision. For theorists who set hbar and c to 1, it works out to (2.3 meV)4. We still have no good theory to explain this value.

Several extensions to the 6 parameter ΛCDM are considered, but none are necessary to fit the data. The non-flat model gives Ωtot = 1.0027 ± 0.0039. This is perfectly consistent with a flat Universe.

The sum of the neutrino masses is < 0.44 eV.

The number of neutrino species is Neff = 2.83 ± 0.38 which is consistent with the standard value of 3.04 for 3 neutrino species. Update 30 Jan 2013: v2 of the papers are posted to the preprint server. With the helium abundance fixed, the number of neutrino species for the WMAP+eCMB+BAO+H0 dataset is 3.84 ± 0.40 which is consistent (at 2σ) with the standard value.

HST Claims it has Uncovered the Most Robust Sample of Distant Galaxies

12/12/12 - The Hubble Ultra Deep Field has been reobserved to greater depth in new filters in the infrared. Here are some highlights from the abstract of Ellis et al.:

To summarize, most previous claims were proven wrong, but a new sample based on the same kind of data is now presented. To be clear, the previous objects still exist but now have smaller estimated redshifts. One previously claimed object is seen again but with the redshift increased by 1.6 to 11.9. I am sure the JWST will sort this out in several years.

Update 04 Jan 2013: Brammer et al. report a tentative emission line in UDFj-39546284 at 1.599 μm, which they feel is probably [O III] at z=2.19.

New CMB Anisotropy Results from the South Pole

29 Oct 2012 - The South Pole Telescope announced new data on the small angular scale anisotropy of the Cosmic Microwave Background. Notable conclusions are:

Inaugural Milner Prizes to Guth & Linde

01 Aug 2012 - Inflation cosmology theorists Alan Guth and Andrei Linde are among the 9 winners of the first Milner Prizes to be awarded. This prize amounts to $3,000,000.

No change in fundamental constants

12 Jun 2012 - Rahmani et al. report that the ratio of the 21 cm line of hydrogen to optical line wavelengths has not changed since 9 Gyr ago. Their limit on the change in a combination of constants x = gp α2 me/ mp is -0.1+/-1.3 parts per million. This makes earlier claims unlikely, since the claimed 10 parts per million change in α would change x by 20 parts per million.

Planck warms up

13 Jan 2012 - The BBC reports that the dilution refrigerator that cools the High Frequency Instrument on the European CMB satellite Planck to 0.1 K has run out of 3He. The Low Frequency Instrument continues to operate at 4 K. The first announcement of cosmological results from Planck is scheduled for Jan 2013.

2011 Nobel Prize for Supernova Cosmology

04 Oct 2011 - Saul Perlmutter, Adam Riess & Brian Schmidt have won the 2011 Nobel Prize in Physics for their work showing the Universe is accelerating by measuring the brightness of distant supernovae. This is evidence for an energy density of the vacuum or a cosmological constant.

Neutrinos faster than Light?

22 Sep 2011 - Here's the paper. But I agree with this reaction: probably not. This experiment did not show that neutrinos arrived 60 nsec earlier than photons, because they could not send photons through the 730 km of rock traversed by the neutrinos. Instead the neutrinos arrive earlier than a prediction coming from a long multi-step calculation. This may become another DAMA imbroglio. Could it be something in the L'Aquila air or water?

Update: 18 Nov 2011 - Nature reports that the OPERA group have repeated their measurement with a new twist. They had previously used a 10,000 ns long pulse of protons to make the neutrinos, but because the pulse had sharp leading and trailing edges and they detected such a large number of neutrinos (over 10,000) they had a good statistical result. The new twist was to use a very short pulse of protons (10 ns long) so they can measure the time of flight accurately with a modest number of neutrino detections (20 in this case). They get the same timing results. This new experiment is included in v2 of the preprint. But they are still using the same clocks so any systematic errors will be the same.

Update 16 Mar 2012 - ICARUS, another detector in the Gran Sasso lab, checked their neutrino times and see them arriving at just the predicted time. This does not confirm the OPERA result.

Multiverse Nonsense in the News

12 Aug 2011 - There has been a spate of news reports about a paper by Feeney etal. But this paper just gets an upper limit, and concludes "the WMAP 7-year data do not warrant augmenting LCDM with bubble collisions". So this is a test of one model of the multiverse but the test came back negative.

The Decline and Fall of the Pioneer Anomalous Acceleration

15 Jul 2011 - Turyshev et al. (2011, PRL accepted) have recovered and analyzed old tracking files on Pioneer 10 and 11, more than doubling the time span of the available data. They find that the anomalous acceleration is decaying with time in a manner consistent with the anisotropic waste heat emission model.

New Most Distant Quasar

30 Jun 2011 - Morlock et al. report on a quasar with redshift z = 7.085 found in an infrared survey. The spectrum has several lines so this a secure redshift. The arXiv preprint appeared on July 4. Note that Nature does allow posting of preprints prior to publication, although these authors did not do so.

Gruber Prize for DEFW

01 Jun 2011 - Marc Davis, George Efstathiou, Carlos Frenk and Simon White have won the Gruber Prize in Cosmology for their early work simulating Universes dominated by cold dark matter.

Gamma Ray Burst Distance Record

25 May 2011 - while chairing a session at the AAS meeting yesterday one the of speakers gave a well founded photometric redshift of z = 9.4 for GRB 090429B. Press conference today and paper on the arXiv submitted. News reports: USA Today, BBC, Bad Astronomy

Binary Star with a 12.75 Minute Period!

25 May 2011 - Warren Brown has found a detached binary with two white dwarf stars orbiting with a 12.75 minute period and a velocity amplitude of 1300 km/sec. This system will merge due to gravitational wave radiation in 0.9 Myr. Update 12-Jul-2011: the preprint is out.

Major New BAO Data Set

17 May 2011 - Blake et al. (2011, MNRAS accepted) report on the results of WiggleZ, which has measured the redshifts of more than 200,000 galaxies and measured the baryon acoustic scale at a redshift of z = 0.6, or 5.7 billion years before now. The measured value of the acoustic scale agrees quite well with the standard ΛCDM model and indicates that the dark energy is behaving like a cosmological constant.

Updated and Expanded Supernova Data Set

11 Apr 2011 - Conley et al. have released a catalog of 472 supernovae so I have updated my supernova cosmology page. The new dataset is quite consistent with previous supernova datasets.

New Hubble Constant

16 Mar 2011 - Riess et al. (2011, ApJ, 730, 119) report Ho = 73.8 ± 2.5 km/sec/Mpc.

z=10 Galaxy?

27 Jan 2011 - Bouwens et al. have gotten a lot of press due to a NASA press release about their candidate z=10 galaxy. While there is nothing wrong with this paper -- a z=10 galaxy would look just like this candidate -- the evidence presented is rather weak. The Hubble Space Telescope saw this object at 1.6 μm wavelength, but not at any shorter wavelengths. This could be due the Lyman α Forest absorbing all the light at wavelengths shorter than (1+z)*0.122 μm = 1.34 μm. It is important to confirm that this object emits at all wavelengths longer than 1.34 μm but the HST is unable to do this due to a design error when it was made: the mirrors are heated to room temperature. As a result the HST is not sensitive to wavelengths longer than 1.6 μm. The JWST will not repeat this error. The Spitzer Space Telescope is not sensitive enough to detect this galaxy.

Planck Early Results

11 Jan 2011 - Planck has released its Early Release Compact Source Catalog and also catalogs of compact cold cores n Milky Way molecular clouds and galaxy clusters found via the Sunyaev-Zeldovich effect. These results are designed to not include any CMB information but they are very interesting nonetheless.

Cosmic Circles[?] = Cosmic Rebirth[?]

28 Nov 2010 - There has been a lot of discussion about a preprint by Gurzadyan & Penrose entitled "Concentric circles in WMAP data may provide evidence of violent pre-Big-Bang activity". I find this very unlikely, and Peter Coles also has his doubts. It is important to remember that this is a Gurzadyan paper, and not a Penrose paper. Update 6-Dec-2010: Moss, Scott & Zibin and Wehus & Eriksen both show that Gurzadyan & Penrose made an error, and that simulated maps using the standard ΛCDM model are fully consistent with the actual WMAP data.

Allan Sandage: 1926-2010

15 Nov 2010 - Word came that Allan Sandage has died. He worked under Hubble as a student. He continued Hubble's work in determining the Hubble constant by measuring the distance and redshift of galaxies. He corrected the Hubble constant from the 500-600 km/sec/Mpc value first found by Le Maitre and Hubble to about 50 km/sec/Mpc. Sandage was then part of a controversy between the "50" camp and the "100" camp led by de Vaucouleurs, which has ultimately been settled in favor of the middle ground, with the best current value of H0=70.4±1.4 km/sec/Mpc.

WMAP: It's a wrap

19 Aug 2010 - WMAP has completed its end of mission calibration observations.

WMAP Retires

10 Aug 2010 - WMAP has stopped taking cosmology data after nine full years of observations, with one extra day to finish the last season of Jupiter observations. There will be a few days of calibration data taken at different precession angles and then WMAP will be done. However, observations of the CMB will continue with the Planck mission which has more frequencies, better sensitivity, and better angular resolution than WMAP.

The thumbnail to the right is a map from Planck released in July 2010. Click to get a larger version.

Geoff Burbidge, 1925-2010

26 Jan 2010 - Geoff Burbidge, a cosmologist famous for working out how all the elements heavier than helium are made in stars, and noted Big Bang skeptic, died today in La Jolla. The high point of his career was the massive paper B2FH, "The Synthesis of the Elements in Stars". The low point of his career was its end, devoted to promoting the Quasi-Steady State Cosmology by publications that verged on fraud. Obituaries in the LA Times, the Wall Street Journal.

Seven Year WMAP Results

25 Jan 2010 - The seven year datasets and papers from WMAP are posted on LAMBDA. Luckily for me, the default parameters in my Cosmology Calculator taken from the first year results are still a good fit to all the data. The image on the right shows a map of the anisotropy of the Cosmic Microwave Background in the three highest frequency bands measured by WMAP: 41, 61 and 94 GHz. Click on the thumbnail for a larger version.

A Sad Loss

22 Jan 2010 - Andrew Lange, a principal in the BOOMERanG experiment and Planck, died today, an apparent suicide. He was very influential in pushing the development of extremely sensitive bolometer detectors in CMB experiments. Update 27 Jan 2010: New York Times obituary.

The legend that BOOMERanG showed the Universe is flat is actually not quite correct, since the results published in 2000 had a serious systematic error. The position of the peak in the angular power spectrum of the anisotropy of the CMB was known to be ellpk = 210 ± 15 in 1999, and BOOMERanG found ellpk = 197 ± 6 in 2000, while the correct value is ellpk = 220. Thus while BOOMERanG provided improved precision, it actually gave a less accurate value for the flatness of the Universe. Since a flat Universe requires Ω=1, and Ω goes like 1/ellpk2, the 10% error in the BOOMERanG value for ellpk really implied a closed Universe. The de Bernardis et al. paper correctly claimed a flat Universe by using strong priors from non-CMB measurements.

Note that Andrew Lange also worked on the MAXIMA experiment which did not have the systematic error, and the systematic error was corrected in 2001. He always worked on the bleeding edge of the possible, and really extended our capabilities in observational cosmology.

New determination of TCMB

11 Nov 2009 - Fixsen has combined velocity maps from the WMAP satellite with the CMB spectra measured by the instrument on the COBE satellite to come up with a quite precise value for the To of the CMB. FIRAS has measured the difference in total CMB power associated with the dipole pattern to an accuracy of 1 part in 700, and since this power varies like (v/c)To4, the well determined velocity measured by WMAP gives a 1 part in 2000 determination of To.

Most Distant Object

29 Oct 2009 - Today's Nature includes the papers about the high redshift (z = 8) gamma-ray burst GRB090423 mentioned earlier. News coverage today: NPR, USA Today, and Universe Today,

Most Distant Cluster?

27 Oct 2009 - Andreon et al. (2009) claim that the cluster JKCS041 is the most distant known cluster of galaxies. Unfortunately they have no spectrographic redshifts so this distance claim must be treated with skepticism until confirmed.

General Relativity Wins Again

17 Sep 2009 - Today's Nature has a letter explaining the anomalous precession of the orbit of DI Herculis by Albrecht et al. 2009, Nature, 461, 373. A preprint is also available. It turns out that the spin axes of the stars are quite mis-aligned with the orbit, leading to tidal torques that explain why the precession was slower than the prediction of General Relativity.
MIT Press Release.
The Cat Herder.

Redshift 8 Galaxies in Infrared

11 Sep 2009 - Bouwens et al. (2009) have posted a preprint describing a set of 5 redshift 8 to 8.5 galaxies in the Hubble Ultra Deep Field. My cosmology calculator gives an age for the Universe of 625 million years for these objects. While these are redshifts based on colors, they appear to be reasonable. A press release is promised for when the paper is accepted, and I expect spectacular new images of the HUDF will be released, but for now admire the HUDF in optical vs infrared from 2004. In 2004 the Hubble had a small IR camera, but even so it could see distant galaxies better in the IR than in the optical. Now it has a big IR camera in the WFC3, and can observe more distant galaxies than before.

Improved Test of General Relativity

02 Sep 2009 - Fomalont, Kopeikin, Lanyi & Benson report on an improved measurement of the deflection of starlight using radio waves and the VLBA. The result agrees quite well with General Relativity. Oddly enough, the press coverage is dated 2 Sep 2009 although the paper was published in the 10 July 2009 ApJ. Also odd is that there was a press release at all, since the previous work using the delay of radio signals from Cassini is 13 times more accurate. But it is nice to know that the deflection of starlight, the experiment that made Einstein famous, agrees with the prediction of General Relativity to one part in 6000. The claim in the press release of 1 part in 30,000 accuracy is just bad arithmetic. [Update 2-Sep-2009 19:28 PDT: I E-mailed Dave Finley at NRAO about the arithmetic problem and he fixed it.]

Planck is cold and getting signals

01 Jul 2009 - Jean-Loup Puget reported today that the Planck HFI was at 0.1 K and signals are being received from the bolometers. This is similar to the startup of WMAP, which took a slower route to L2 but did not need to be as cold. WMAP made its first data release 587 days after launch. Let's see if Planck can match WMAP: 21 Dec 2010 would be that goal.

The lowest commandable 3He rate is giving good cooling so the prospects are good for a two-year mission.

UPDATE: 17 Sep 2009 - Planck has released first light images.

Spitzer Warming Up

15 May 2009 - After 2090 days of cryogenic operation in space, the Spitzer Space Telescope has used up its entire stock of liquid helium and is warming up. I first worked on Spitzer when it was the Shuttle Infrared Telescope Facility in 1976.

Big Day for Space-Based Astronomy: Planck, Herschel, Hubble

14 May 2009 - Herschel and Planck have launched! ESA has a page listing the latest press releases. Herschel is a 3.5 meter diameter far-infrared telescope. The BLAST balloon-borne large sub-millimeter telescope was a test of one of the Herschel intruments. I first heard about Herschel when it was called FIRST and was an 8 meter telescope, back in the early 1980's. At that time NASA was planning to build a a 20 meter far-infrared telescope call the Large Deployable Reflector. In 1980 this NASA project was called LADIRT. Planck is a new CMB anisotropy mission many times more sensitive than WMAP and also covers a larger range of frequencies with better angular resolution. It should do very good work on small angular CMB anisotropy and the Sunyaev-Zeldovich effect. And the first of many planned spacewalks during the STS-125 mission to repair the Hubble Space Telescope is going well today.

More Accurate Hubble Constant

07 May 2009 - Riess et al. report a new value for the Hubble constant of Ho = 74.2 +/- 3.6 km/sec/Mpc based on Cepheid measurements in galaxies that have hosted Type Ia supernovae, including the nuclear ring maser galaxy NGC 4258 which has a very precise distance determined by geometric means.

Highest Redshift GRB Seen

28 Apr 2009 - NASA and the CfA issued press releases about a gamma-ray burst that went off on 23 April 2009, known as GRB 090423. The burst showed a fading infrared transient but no flux in the optical. In fact there was no flux shorter than 1.1 microns. If this edge is assigned to the Lyman α forest edge at 122 nm, then the redshift is z = 8. No paper has been submitted to the preprint server, but a collection of GCN Circulars is available. Update 8 Jun 2009: Tanvir et al. and Salvaterra et al. have been posted.

BLAST Results on the Far Infrared Background

09 Apr 2009 - BLAST has published results in today's Nature: Devlin et al (Nature, 2009, 458, 737) showing that half of the CIRB at 250 to 500 micron wavelengths comes from redshifts less than 1.2, and half comes from redshifts greater than 1.2. The arXiv version includes the supplemental information. A more complete paper discussing these results is Marsden et al.

More Bigger Milky Way

24 Feb 2009 - The Reid et al. paper describing the press announcment is finally on the preprint server. The value for the distance from the Sun to the Galactic Center is 8.4 +/- 0.6 kpc. The rotational speed at this distance from the Galactic Center is 254 +/- 16 km/sec. Allowing for the 5.3 km/sec peculiar velocity of the Sun in the direction of Galactic rotation, a predicted proper motion for the Galactic Center of 6.50 +/- 0.20 milli-arcseconds/year is found compared to the observed proper motion 6.379 +/- 0.024 milli-arcseconds/year. This rotation speed is very similar to the rotation speed of Andromeda at the same radius, implying that the Milky Way and Andromeda are very similar in mass. This represents an increased mass for the Milky Way.

An Extragalactic Radio Background?

07 Jan 2009 - The ARCADE experiment reported ( NYT, Science News, GSFC press release) the existence of an extragalactic radio background. But this signal has the same spectrum as the radio emission from the Milky Way, and could well be due to an error in determining the galactic contribution to the total signal. The papers are available here, here, here and here. The ARCADE data are beautiful but mainly cover higher frequencies where the extragalactic radio background is not detectable, so the "ERB" depends on a debatable assumption about the lower frequency data, which are all tied to the Haslam 408 Mhz map, published in 1981, but with a zero point set using Pauliny-Toth & Shakeshaft, published in 1962! Pauliny-Toth & Shakeshaft certainly did not see an ERB or even the CMB in their data. Update 26 Nov 2010: Guzman et al. give a much smaller ERB estimate.

A Bigger Milky Way

05 Jan 2009 - Mark Reid reported at the AAS meeting on very precise distances to radio masers that have led to an increase in the estimated size and rotation velocity of the Milky Way (NYT, BBC). The distance scale scale and velocity both increase by 15 percent so the angular velocity stays about the same. This leads to a 50 percent increase in the estimated mass of the Milky Way.

Dark Flow Detected - Not!

24 Sep 2008 - Kashlinsky et al. (2008) have claimed a detection of a bulk flow in the motion of many distant X-ray emitting clusters of galaxies. Unfortunately this paper and the companion paper have several errors so their conclusions cannot be trusted. A technical discussion of these errors can be found here.

Meet the Fermi Gamma-ray Space Telescope

26 Aug 2008 - NASA released an all sky map in gamma rays from the satellite formerly known as GLAST, newly renamed as the Fermi Gamma-ray Space Telescope or FGST. Enrico Fermi discovered the Fermi-Dirac statistics followed by particles known as fermions, such as electrons and protons, emigrated to America to escape fascism, and built the first nuclear reactor as part of the Manhattan Project. FGST will have greatly improved angular resolution and sensitivity for high energy gamma rays with E > 1 GeV at the short wavelength end of the electromagnetic spectrum, and should discover thousands of gamma ray sources at cosmological distances.

Variable Constants?

20 Jun 2008 - Murphy, Flambaum, Muller & Henkel (2008) show that the ratio of the proton mass to the electron mass has varied by less than 1.8 parts per million (95% CL) since redshift z = 0.68466. They compared the radio inversion lines of ammonia to the pure rotation lines of HCN and HCO+. All of these lines are measured very precisely using radio astronomy techniques, and the redshifts are consistent. But the ammonia lines are much more sensitive to the proton:electron mass ratio so this quantity has not varied in the past 6 billion years. This report is an improvement over previous results using the same quasar absorption line cloud.

Another Bullet Cluster

17 Jun 2008 - Bradac et al. (2008) have found another bullet cluster where two clusters of galaxies have collided, leaving the hot gas in between the clumps of galaxies, but the source of gravity has passed right through the collision, staying with the galaxies. Since the hot gas is most of the normal matter, this shows that the source of gravity is not the normal matter, but rather dark matter. This is a problem for alternative models that modify gravity to eliminate the need for dark matter.

Supernova Initial Flash

22 May 2008 - Soderberg et al. report an observation of a soft X-ray flare from a spot that later turned out to be a Type Ibc supernova. The peak flux was about 7 x 10-10 erg/cm2/sec for about 400 seconds. At the 27 Mpc distance of the host galaxy NGC 2770 this is about 2 x 1046 ergs in X-rays produced when the shockwave breaks out of the massive star whose core has collapsed. The UV peaked a day later, and the optical 20 days later as the remains of the star expanded and cooled.

This was quite an interesting result when it appeared three months ago on arxiv.org, but it was embargoed by Nature until publication so I didn't post this news item until now.

New High Redshift CMB Measurement

13 May 2008 - Srianand et al. have announced a measurement of TCMB at a redshift of 2.418. Absorption lines from carbon monoxide (CO) molecules were seen in the spectrum of a distant quasar, and showed rotational excitation in the CO ground vibrational state. The temperature seen is 9.15 +/- 0.7 K, while the Big Bang model predicts 9.315 K. So this observation is consistent with the Big Bang, but contradicts the Steady State model.

New Union Supernova Catalog

28 Apr 2008 - Kowalski et al. (2008) of the Supernova Cosmology Project present a union catalog of supernovae. The catalog contains 332 SNe that pass all cuts when the low redshift SNe are included. Click on the thumbnail at right for binned ΔDM vs. redshift tables and plots. ΔDM is the difference in the distance modulus between the data or model and an empty Universe model. A higher distance modulus means the supernovae are fainter than expected in an empty Universe.

Tired Light is Still Dead

24 Apr 2008 - Blondin et al. (2008) studied distant supernovae using spectra to judge the age of the object during each observation. They found an aging rate that varied with redshift z like

1/(1+z)(0.97 +/- 0.10),
compatible with the expected 1/(1+z) for expanding Universes, but 9.7 standard deviations away from the constant aging rate expected in the tired light model.

Dark Matter Detected?

17 Apr 2008 - The DAMA/LIBRA experiment announced a confirmation of their previously found annual modulation signal in the count rate of a deep underground CsI detector. They see a modulation of +/-0.027 counts/kg/keV/day in the 2.5 to 3.5 keV band, but since the amplitude of modulation is supposed to be at most 7% of the dark matter signal this implies a dark matter generated event rate of 0.38 cts/kg/keV/day or more. The total rate in the experiment is 1.24 cts/kg/keV/day in this 2.5-3.5 keV band, so the dark matter rate is at least 31% of the total. With such a large fraction of the total rate coming from dark matter events in this 3 keV bump one would expect to see a corresponding bump in the total rate spectrum and it is actually present. But the CDMS experiment in the Soudan mine saw no counts in 397.8 kg-days of exposure, so the high DAMA/LIBRA rate seems unlikely - but not impossible given the differences in the detector materials and methods. However, it is peculiar that the annual modulation technique is being used when the ratio of dark matter to background counts is this large.

Naked Eye Visible Gamma Ray Burst Afterglow from z=1!

19 Mar 2008 - The NASA satellite Swift has detected the most luminous explosion yet seen. Gamma Ray Burst GRB080219B got slightly brighter than optical magnitude 6, the limit of naked-eye visibility, and has a redshift greater than or probably equal to 0.937, the higher of two absorption line redshifts. The absolute magnitude is then -38! The press is catching up to this story: the New York Times, the Associated Press, and the Agence France Presse all have articles on this. Here is the NASA press release.

WMAP 5 year Data Released

5 Mar 2008 - WMAP released its five year dataset today, with 7 papers and new maps and power spectra posted to LAMBDA. Highlights of the new results include:

The image at right is a new combined CMB power spectrum showing that a 6 parameter ΛCDM model still fits all the CMB data as well as the Baryon Acoustic Oscillation signal and the supernova data. Click on the image for a larger version.

Supernova Progenitor Seen? - Probably Not

15 Feb 2008 - Roelofs, Bassa, Voss & Nelemans (2008) comment on the claimed detection by Voss & Nelemans (2008, Nature, 451, 802) of an X-ray binary progenitor at the position of the Type Ia supernova SN 2007on. They find that the X-ray source is probably still present, although significantly fainter. Furthermore, with better astrometry the X-ray position is slightly offset from the position of the supernova, by 1.18+/-0.27 arc-seconds. Since a Type Ia supernova completely disrupts the white dwarf that explodes, a surviving X-ray source is very unlikely. So the putative progenitor was quite possibly a chance coincidence with a variable X-ray source.

Highest Redshift Galaxy? but no lines

12 Feb 2008 - The HST and the Spitzer Space Telescope have issued a press release claiming the detection of a galaxy at redshift z=7.6. However, NO lines have been observed. Based on previous z=10 galaxies, we should require two lines before believing any story like this. The NASA budget must be tight.

Very Precise Distance to a Cepheid

11 Feb 2008 - Kervella et al. report a distance to the Cepheid variable RS Puppis of 1992 +/- 28 parsecs. This distance was obtained geometrically using a light echo technique. Cepheids are used to calibrate the Hubble constant that determines the age and size of the Universe. ESO has issued a press release. The paper will be published in Astronomy & Astrophysics.

Quasi-Steady State Cosmology Fails Again

18 Jan 2008 - Narlikar, Burbidge and Vishwakarma (2007, J. Astr. & Ap., 28, 67) claim to fit the CMB anisotropy data with the QSSC model. Not surprisingly, this claim is false.

Crafoord Prize to Sunyaev

17 Jan 2008 - the Crafoord Prize in Astronomy and Mathematics was split between Rashid Sunyaev and two string theorists. Sunyaev is famous for the Sunyaev-Zeldovich effect and other studies of the Cosmic Microwave Background. Born and raised in the Soviet Union, Sunyaev is now director of the Max Planck Institute for Astrophysics in Garching near Munich.

Not Much Evidence for Cosmic Texture

07 Dec 07 - What is essentially a 1.4 standard deviation result is in today's Science: Cruz et al. (2007, Science, 318,1612), a paper that explains the giant hole in space by an unwinding texture event. A texture is a topological defect like a cosmic string, and the model that cosmic structures were created by topological defects was ruled out by COBE. But it is always possible that a small fraction of cosmic structures are created by topological defects, and Cruz et al. consider a model where that small fraction is just one cosmic defect matched to the "cold spot" in the Cosmic Microwave Background (CMB) found by WMAP. They find a likelihood ratio of 2.5 to 1, which is normally considered to be exp(n2/2) where n is the number of standard deviations.

Cruz et al. do not consider the giant void found in the direction of the cold spot. If both the cold spot and the void can be explained by texture their model would gain in credibility.

Giant Hole in Space?

23 Aug 2007 - There is a widely picked up press release about results by Rudnick et al. (2007, ApJ in press) on explaining a WMAP cold spot reported earlier. The original report on the WMAP cold spot was statistically weak since the authors searched through roughly 100,000 combinations of position and resolution, so finding an oddly cold spot was not too surprising. But the new result shows that the WMAP cold spot coincides with an anomalous spot in the radio survey NVSS. Rudnick et al. have interpreted this as a very large void in the distribution of matter in this direction, causing the cold spot via the late-integrated Sachs-Wolfe effect. However, they have no distance information on the sources in the spot so the interpretation is still uncertain. But the coincidence between the WMAP cold spot and the NVSS low source count spot is intriguing.

The timing of the press release is a bit unusual, since the paper was released on the preprint server in April, and has not yet appeared in print, so neither of the usual hooks for timing press releases was used.

UPDATE: 19 May 2008 - Smith and Huterer find no evidence for the void in the NVSS.

Supernova researchers win the Gruber Prize

17 Jul 2007 - The winners of the Gruber Prize in Cosmology were announced today. The winners are Saul Perlmutter and the Supernova Cosmology team; and Brian Schmidt and the Hi-z Supernova Team. In 1998 these groups used supernova observations to discover dark energy. The prize amount has been doubled since the COBE team won last year.

Redshift 10 Galaxies?

12 Jul 07 - Stark et al. claim to have detected Lyman alpha emission from 6 candidate objects with redshifts between 8.5 and 10.2. These are very faint sources which have been magnified by the gravitational lensing of a foreground cluster of galaxies, and even then barely detected with very long exposures on the Keck telescopes. The negative image at right shows a near infrared image taken with the Hubble Space Telescope, and it is clear that whatever there is in the center of the circle is very faint. But when the light coming from the center of the circle is spread out into a spectrum using the NIRSPEC instrument built at UCLA there is an easily visible clump in the spectral image, shown at left. This is also a negative image, so the dark spot in the center of the circle is an emission line. This spectral line is at a wavelength of 1.355 microns, which is 11.1 times longer than the rest wavelength of Lyman alpha, so if it really is Lyman alpha, the redshift of this source is 10.1. Using my cosmology calculator, one finds that the age of the Universe was 475 million years when this galaxy emitted the light that we see. That light took 13.190 billion years to reach us, and the galaxy is now 31.578 billion light years away from us due to the expansion of the Universe.

One note of caution: a previous claimed redshift 10 galaxy based on the same kind of evidence was not confirmed.

Variable Constants?

21 Jun 2007 - A new study of ammonia and carbon monoxide lines in a distant quasar shows that the electron to proton mass ratio has remained quite constant. Earlier work with ultraviolet lines of molecular hydrogen, redshifted into the optical, suggested a small change in this ratio, but this new study uses radio astronomy which allows much more precise measurements of line ratios.

Underground Laboratory Cosmology

09 Jun 2007 - Today I visited the Soudan Underground Laboratory near Tower, MN. This is in an old iron mine in the Mesabi Iron Range, where hematite (70 percent iron by weight) was brought up from nearly 0.8 km underground. It is run as a state historical park, so you can tour the engine house and see the antique hoist, then hear the antique hoist crank up and lift the previous tourists out of the mine. Then you put on your hard hat, get in the 1.2 meter square cage and go down into the Earth. In the physics lab the lights and air handling system let you forget you are so deep underground, and you find the MINOS far detector. MINOS stands for Main Injector Neutrino Oscillation Search, and is an experiment that generates a neutrino beam at Fermilab near Chicago, and send the neutrinos through 800 km of rocks to the Soudan Underground Laboratory. There the 6000 ton MINOS far detector sees about 2 or 3 neutrinos per day. Everything you see in the physics laboratory had to go down in the 1.2 meter square cage! The MINOS detector sees many cosmic ray muons and you can see the latest event on the Web.

The MINOS experiment has confirmed the earlier results of the Super-Kamiokande experiment that used atmospheric neutrinos. It appears that muon neutrinos oscillate into tau neutrinos indicating a difference in mass squared of about 0.0025 eV2. While neutrino oscillation experiments only measure delta mass squared values, this result indicates that neutrinos are probably not the cosmological dark matter, since if the tau neutrino has a mass of 0.05 eV, and the muon and electron neutrinos are much lighter, then neutrinos make up only 0.1 percent of the critical density of the Universe, and the current model has 23 percent of the critical density in dark matter.

The other cosmological experiment in the Soudan lab is the Cryogenic Dark Matter Search (CDMS). This experiment is searching for dark matter made up of WIMPs. So far it only has measured upper limits.

Einstein 1, GP-B 0

14 Apr 2007 - Preliminary results from the GP-B mission were reported at the APS meeting in Jacksonville, FL today. Everything is consistent with the predictions of General Relativity, but the accuracy achieved to date is disappointing. There is a good post on this at Cosmic Variance.

There were two major glitches in the GP-B experiment:

So the overall results to date are that the geodetic precession of -6606 milli-arcsec/yr is measured to be about -6618 +/- 97 milli-arcsec/yr, and the frame dragging effect of 39 milli-arcsec/yr is uncertain by the same roughly 100 milli-arcsec/yr systematic error estimate.

Further data analysis may reduce this uncertainty. But Murphy, Nortvedt & Turyshev claim that lunar ranging has already verified the frame dragging effect to 1 part per thousand, and GP-B is very unlikely to get a final accuracy close to this precision.

More Data on Variable Constants

05 Mar 2007 - A new preprint gives results on the change in the fine structure constant alpha. for a quasar at z = 1.84. The change is insignificant and in the opposite direction to earlier reports. The fine structure constant is probably constant. Here is a graph of all the results.

More Supernova Data

04 Jan 2007 - Wood-Vasey et al. (2007) and Miknaitis et al. (2007) present data from the ESSENCE supernova project. I found that their distance moduli were 0.106 mag higher than those in Riess et al. (2007) on the low redshift calibration set in common, so I subtracted this constant and added the ESSENCE supernovae to the Riess etal (2007) dataset. There is enough scatter in this ΔDM to make me think that this combination of datasets will have to done again by someone in one of the supernova teams, but I give it here for a first look analysis. Click on the small plot at right to see the resulting plot, and find the binned data table toward the bottom of my supernova cosmology page. There is no great change to the picture, but it is good to see another group getting consistent results on supernovae.

Of course some of the parameter estimates reported in Wood-Vasey et al. (2007) are absurd. Figure 13 showing the limits on the dark energy equation of state shows w(z) = w0 +wa(1-a) with (w0, wa) = (-1.7,3) as being within the 1 sigma contour. But this combination gives a dark energy density much larger than the matter density at last scattering. This is a consequence of not having enough data to constrain the variable w. But the take home message, "A w = -1, flat-Universe model is consistent with our data" makes perfect sense.

IR Fluctuations: z > 7 Objects?

18 Dec 06 - Kashlinsky et al. issued a press release claiming that fluctuations in the background of deep infrared images from the Spitzer Space Telescope are due to very distant objects with high redshifts, z > 7. But Cooray et al. show that masking faint galaxies visible in HST images eliminates the fluctuations seen by Kashlinsky et al. These HST galaxies have photometric redshifts in the range 1 < z < 2. This redshift range corresponds to the well known peak in star formation, so there is nothing surprising or newsworthy in the IR fluctuations. Full disclosure: I am a co-author on Cooray et al.

So the answer to the question in the title is: NO! As is always must be, according to Hinchliffe's rule: if the title is a question, the answer is `no'.

Cosmology Using Gamma-Ray Bursts

12 Dec 06 - Brad Schaefer has posted his paper about the gamma-ray burst (GRB) Hubble diagram. I have binned data from the table in this paper to compute the luminosity distance vs. redshift and used it to extend my plot based on supernovae. While the GRB distances derived by Schaefer are quite imprecise relative to the accuracy obtained with supernovae, they extend to much higher redshifts. This new data is consistent with the consensus flat vacuum energy dominated ΛCDM model, but it is not consistent with the closed vacuum dominated model that fit the supernova data alone. Click on the small graph at right for a larger version. It shows that the high redshift data is useful for constraining the geometry of the Universe. Both an equation of state different than w=-1 or a non-flat Universe with Ω not equal to 1 affect the distance vs redshift starting at order z3, so these parameters are hard to separate at low and moderate redshifts. Getting high z data helps considerably.

New Data on Dark Energy from High z Supernovae

16 Nov 06 - NASA held a press telecon today about dark energy, but neither the press release nor the images accompanying it contained any useful information.

UPDATE: 20 Nov 06 - The Riess et al. paper has reached the preprint server and provides the information the press office stripped out. The paper assumes that the Universe is flat when trying to find the properties of the dark energy, and bases this assumption on the fact that a flat Universe with a cosmological constant fits all the available data. Therefore the conclusion of this paper, which is that the dark energy looks like a cosmological constant, is built into the assumptions. This analysis is not sound logic. But the data are sound, and everything remains reasonably consistent with a flat Universe with a cosmological constant. I have updated my supernova cosmology page using these new results.

MAXIPOL CMB Polarization Results

14 Nov 2006 - Two preprints describing the instrument and the data analysis for the MAXIPOL balloon-borne polarization experiment were posted today. The data were taken 3.5 years ago, and the final results are an E-mode polarization amplitude of 55+51-45 μK2 in the range of angular scales from 0.3 to 1.2 degrees. The prediction from the standard flat vacuum-dominated ΛCDM cosmology with accelerating expansion is 14 μK2. This result is consistent with the standard model but also consistent with zero. The South Pole-based experiment DASIPOL got better results earlier

Nobel Prize for COBE

03 Oct 2006 - John Mather and George Smoot have won the 2006 Nobel Prize in Physics for their work on COBE. Mather was the PI on FIRAS, the instrument to measure the spectrum of the Cosmic Microwave Background (CMB). Smoot was the PI on the DMR, the instrument to measure the anisotropy of the CMB. Of course many others including myself worked on COBE. See my E-mail to the COBE team announcing the discovery of the DMR signal, which is part of my view of the history of the CMB up until WMAP which is still observing. John Mather mentioned the October 1991 draft paper I presented to the COBE Science Working Group in his book, "The Very First Light".

Egg-shaped Universe? Probably Not

30 Sep 2006 - The Los Angeles Times has a story today about the paper that suggests the Universe might be egg-shaped, and that this might explain the low quadrupole seen in the WMAP (and COBE DMR) CMB anisotropy maps. This was a silly paper and I said as much to the reporter John Johnson. Adding an additional quadrupole from the ellipsoidal Universe will make the probability of the low observed quadrupole even smaller, unless there is a reason that the quadrupole from the ellipticity will be equal and nearly opposite to the quadrupole from inflation. No such reason is given in this paper. Unfortunately the referees for the Physical Review Letters missed this, and the American Institute of Physics issued a press release (subscription) about the paper.

Four Precise Tests of General Relativity

14 Sep 2006 - Kramer et al. report on an analysis of 2.5 years of timing data on the double pulsar in a paper published in Science Express (subscription) online on 14 Sep 2006. The printed version will appear in Science. The neutron stars masses are now 1.3381 +/- 0.0007 and 1.2489 +/- 0.0007 solar masses. Four post-Keplerian parameters of the binary are determined and all agree with GR, to accuracies of 0.3 +/- 1.4%, 0.36 +/- 0.68%, 0.013 +/- 0.05%, and 0.9 +/- 0.55%.

New Record Redshift

14 Sep 2006 - Iye et al. report a galaxy at z=6.96 with a one line redshift. Since the reported z=10 galaxy fell apart, this is the highest redshift spectroscopically measured to date.

BOOMERanG PIs win Balzan Prize

6 Sep 2006 - Andrew Lange and Paolo de Bernardis have won the Balzan Prize for their work with the CMB anisotropy experiment BOOMERanG. Of course the first BOOMERanG results were miscalibrated, giving a 10% error in the acoustic scale, but this was corrected in 2001.

More on Dark Matter

21 Aug 2006 - NASA announced updated information about the "bullet cluster" 1E0657-56 today. Two clusters of galaxies have recently collided in this X-ray source. This cluster is filled with hot gas so X-ray observations by the Chandra X-ray Observatory show where the ordinary matter is located. 90% of the ordinary matter (the "baryonic" matter) is hot gas. The new results [Clowe et al., Bradac et al.] use gravitational lensing of background galaxies to show where the sources of gravity are located. The sources of gravity in the cluster are not located where the ordinary matter is located, so this cluster is a counter-example to MOND. All of this was known in 2003 but with less precision. Sean Carroll has a nice post about this at Cosmic Variance.

I have set up a page that blinks back and forth among different views of this cluster.

John Mather and the COBE Team win the Gruber Prize

15 Aug 2006 - The Gruber Prize in Cosmology was awarded to the COBE team at the IAU meeting in Prague today. That includes Ned Wright. [Physics Web].

Cepheid and Maser Distances Agree

11 Aug 2006 - Macri et al. give a Cepheid distance to NGC 4258, where Herrnstein et al. found a distance of 7.2 Mpc based on observing the velocity and angular radius of a disk of masers around the nucleus, and both the angular velocity and the centripetal acceleration of the masers. Cepheids in NGC 4258 were 10.88 magnitudes fainter than Cepheids of the same period in the LMC giving a distance of 48 +/- 2 (random) +/- 3 (systematic) kpc for the LMC. This agrees very well with the light echo distance of 47 +/- 1 kpc for the LMC based on SN 1987A.

The final value for the Hubble constant is Ho = 74 +/- 3 (random) +/- 6 (systematic) km/sec/Mpc which agrees very well with the current concordance models. Oddly enough, the second author on this paper is also the second author on another recent result that claims a significantly lower value for Ho. But none of the recent differences in Ho determinations come close to the old Hubble constant wars between the Sandage and de Vaucouleurs camps.

An Older but Larger Universe?

05 Aug 2006 - Ohio State astronomers have measured a new precise distance to the nearby galaxy M33 based on a spectroscopic eclipsing binary. Their value is 15% larger than the old Cepheid based distance. By itself this says nothing about the Hubble constant because M33 is so close to the Milky Way that its radial velocity is dominated by random motions, not the expansion of the Universe. But it could indicate that Cepheid distances are incorrect by 15%.

If so, the Hubble constant would be smaller: about 62 instead of 72 km/sec/Mpc. But the claim in the OSU press release that "the universe could be [...] 15 percent older" is incorrect. If the Hubble constant is lower, then CMB anisotropy data require that OmegaM, the ratio of the matter density to the critical density, be higher, so the vacuum energy is lower, and the change in the age of the universe is considerably smaller, as shown in graph at right above [click on the graph to enlarge] which shows the age vs. Ho for CMB consistent models as the solid curve, and the 1/Ho behavior assumed by the OSU press release as the dashed curve. So the Universe would not be 15% older but perhaps 7% older.

The claim that the Universe would be 15% larger is partially incorrect. Even though relatively nearby galaxies would be 15% further away the actual size of the Universe would go from infinite (flat) to finite (closed) but very big, which is a smaller Universe. The distance to distant quasars at redshift z=6 would increase by only 4%, and the distance to the last scattering surface changes less than 0.5% because this is what is fixed by the CMB.

CNN quoting space.com and John Johnson of the LA Times accepted the press release's claims of a 15% older and larger Universe uncritically. The real news is that a new method for precision distance measurements has achieved its first result. It will be averaged in with other methods used to calibrate the Cepheid period-luminosity relation and lead to a few percent decrease in the Hubble constant.

One of the methods to be averaged will be the Sunyaev-Zeldovich effect which gives Ho = 77 +/- 10 km/sec/Mpc according to a recent paper. This agrees with the values of Ho from WMAP and HST quite well.

The End of the Space Age?

31 Jul 2006 - Today's Space News has a graph of launches to Earth orbit or beyond per year since 1957. 2005 had the fewest launches since 1961. If you think this is a bad thing, write your Congressman and Senators! Competitively selected small unmanned science missions like the Explorer and Discovery programs have been particularly hard hit by the underfunding of the Vision for Space Exploration.

Click on the thumbnail at right for a larger version.

ARCADE Takes Off Again

21 Jul 2006 - The balloon experiment ARCADE was launched from Palestine, TX today. ARCADE measures the precise temperature of the CMB at longer wavelengths than the precise data from the FIRAS instrument on the COBE satellite. ARCADE's previous flight was on 28 July 2005.

Spitzer Finds Distant Clusters of Galaxies

5 Jun 2006 - Mark Brodwin announced new results from the Spitzer Shallow Survey at the AAS meeting today. This survey of 9 square degrees in Bootes was done about as done about as rapidly as the Spitzer Space Telescope can operate, but even with very short exposures, the power of infrared observations means that very distant galaxies can be seen. Of course no redshifts are given in the press release because of the "five W's but no z" rule taught in science journalism schools, and the only distance given is the light travel time distance, Dltt = Dumb. But using my cosmology calculator I find that for Ho = 71 km/sec/Mpc, OmegaM = 0.27 in a flat, lambda-CDM Universe, the given Dltt = 9.1 billion light years means a redshift z = 1.41. What is the significance of the square root of 2 as a redshift? None whatsoever, since it is 1+z that gives the expansion factor of the Universe since the light was emitted.

Finally an Odd Lens

23 May 2006 - Theory suggests that gravitational lenses should have an odd number of images, but most multiply imaged lenses have shown 2 or 4 images. We assume there is a faint image near the center of the lens that we cannot see. But now the HST has seen a five-image lens. The infrared camera NICMOS on HST had earlier seen a 3 image lens ( Ibata et al. 1999, AJ, 118, 1922).

WMAP Second Data Release

16 Mar 2006 - The WMAP satellite announced results from its first 3 years of operation today. The new data is best all-sky measurement of the anisotropy of the CMB to date. The improvements over the first WMAP data include polarization data; improved knowledge of the beam profiles, gain and pointing; and of course better signal to noise ratio. The polarization data allows the optical depth due to electron scattering since reionization to be determined. This parameter tells us when the Universe became reionized by the first generation of hot blue stars -- about 400 million years after the Big Bang. It is now possible to rule out certains types of models for the inflationary scenario.

Pulsar News from the AAS meeting

12 Jan 2006 - Two newsworthy pulsars were announced: J1906+0746 is a young binary pulsar with a 0.144 second spin period in a 3.98 hour binary orbit, and it indicates that the rate of binary pulsar formation is larger than previously thought. As a result, LIGO will have perhaps twice as many "binary pulsar deaths" to observe than had previously been thought.

The second interesting pulsar is a binary pulsar that is spinning at 716 revolutions per second. This is the fastest known spin rate, and replaces a previous record of 642 rps that stood for 24 years. This pulsar is located in the globular cluster Terzan 5, one of 33 pulsars now known in this cluster. The orbital period is 1.0944303 days, and the orbit is circular.

Revisiting Variable Constants

click for larger version 13 Dec 2005 - A new preprint claims to have achieved a much higher accuracy in measuring the variation in the fine structure constant, alpha. The previous claim to have seen a variation, which was viewed with skepticism, is based on the red data points, while the blue points show the 21 cm results and the new paper gives the black point which is consistent with no variation in the physical constants.

Hermann Bondi, founder of the Steady State, dead at 85.

10 Sep 2005 - Sir Hermann Bondi, co-founder of the State State model with Thomas Gold and Sir Fred Hoyle, died on 10 Sep 2005 at the age of 85. With his passing the three main architects of the Steady State cosmology have passed on. Bondi was the author of an excellent book on relativity, "Relativity and Common Sense".

Bad News in X-Ray Astronomy

10 Aug 2005 - The high resolution X-ray spectrometer XRS on the Japanese Suzaku (formerly Astro-E2) mission has failed due to a cryostat failure. The XRS was originally to be on AXAF, now the Chandra X-ray Observatory. It was then on Astro-E which had a launch failure. Astro E2 launched successfully on 10 Jul 2005.

ARCADE Takes Off Again

28 Jul 2005 - The balloon experiment ARCADE was launched from Palestine, TX today. ARCADE is designed to measure the precise temperature of the CMB at longer wavelengths than the precise data from the FIRAS instrument on the COBE satellite. ARCADE's previous flight measured T=2.721+/-0.01 K at 3 cm wavelength ( Fixsen et al., 2004, ApJ, 612, 86-95). This is consistent with the T=2.725+/-0.002 K measured by FIRAS from 0.5 to 0.05 cm wavelengths.

New Age for the Universe

30 Jun 2005 - This week's Nature has a letter giving a new determination of the age of the Universe based on the age of the isotopes. 238U and 232Th are both radioactive with half-lives of 4.468 and 14.05 Gyrs but the uranium is underabundant in the Solar System compared to the expected production ratio in supernovae. This is not surprising since the 238U has a shorter half-life, and the magnitude of the difference gives an estimate for the age of the Universe. But the production ratio is poorly known from nuclear physics models, so Dauphas (2005, Nature, 435, 1203) combines the Solar System 238U:232Th ratio with the ratio observed in very old, metal poor stars to solve simultaneous equations for both the production ratio and the age of the Universe, obtaining 14.5+2.8-2.2 Gyr.

BLAST in the air

12 Jun 2005 - The Balloon-borne Large-Aperture Submillimeter Telescope (BLAST) launched from Sweden today, with a planned long duration flight to Alaska. This 2 meter diameter telescope is even larger than the 102-cm balloon-borne far infrared telescope that formed the basis for Ned Wright's PhD thesis. BLAST will observe many luminous distant dusty galaxies. The track of BLAST can be followed live on the Web. The actual landing was in Canada on 16 Jun 2005, following a 101 hour flight.

Infrared Echo of a Magnetar Burst?

9 Jun 2005 - The Spitzer Space Telescope observed very rapidly moving filaments outside the Cas A supernova remnant (Krause et al., 2005, Science, 308, 1604). These are probably "light echoes" caused by a spherically spreading shell of radiation moving out at the speed of light. But the extrapolated time for the creation of the shell is only 50 years ago, while the Cas A supernova exploded 325 years ago. So one hypothesized cause could be a "magnetar burst" like the burst from SGR 1806-20 on 27 Dec 2004 (Hurley et al., 2005, Nature, 434, 1098). The giant bursts from these Soft Gamma Ray repeaters have very brief and energetic initial pulses that have been proposed as the source for the short-hard gamma-ray bursts seen by BATSE. But another theory is that short-hard gamma-ray bursts are due to two neutron stars merging to form a black hole.

Cosmic Ripples instead of Dark Energy?

16 Mar 2005 - Rocky Kolb et al. have suggested that large scale ripples in space-time could explain the observations of the accelerating Universe that seem to require dark energy - the vacuum energy density that is equivalent to the cosmological constant. Despite issuing press releases and getting some coverage, even in the Los Angeles Times although 10 days later, I find the Kolb et al. arguments lacking. In Einstein's General Relativity, the local metric determines the local stress-energy tensor, so the large scale ripples do not change the need for a negative pressure and hence a vacuum energy density or cosmological constant based on the supernova observations of the local geometry of space-time. Here local means within about 10 billion light years (!) but we can easily observe a region this large. Hirata & Seljak also disagree with Kolb et al., as do Geshnizjani, Chung & Afshordi and Flanagan. This could be a case where the effects of good Italian wine overwhelmed the scientific super-ego of Kolb et al.

Cosmic Ripples Seen by Galaxy Surveys

11 Jan 2005 - Both the Sloan Digital Sky Survey and the 2 Degree Field Galaxy Redshift Survey reported the discovery of features in the distribution of nearby galaxies that correspond to the oscillations seen in the anisotropy of the Cosmic Microwave Background for several years. The overall statistical significance of this result is good but not great: 3.5 standard deviations. But observations of these ripples provide two valuable new constraints on cosmological models, and verify the current Lambda-CDM model of the Universe. The detection of these ripples is shown at right in a version of Figure 3 from a technical paper describing these results. It gives a matter density in gm/cc that agrees with the value found by WMAP. Both WMAP and the SDSS measure this density to a precison of 8% and their values agree to within 5%. Combining the CMB and SDSS data gives an improved limit on the total density of the Universe: Omegatot = 1.01 +/- 0.009. If Omegatot = 1, the Universe is flat; if Omegatot > 1 the Universe is closed; while if Omegatot < 1 the Universe is open.

General Relativity Passes a Test

21 Oct 2004 - General relativity, the theory of gravity that provides the basis for almost all cosmological models, predicts that a massive rotating body produces a "frame-dragging" effect that will cause nearby gyroscopes to precess relative to the distant stars. Ciufolini & Pavlis (2004, Nature, 431, 958) used the orbits of the LAGEOS and LAGEOS II satellites as gyroscopes to test this prediction and find a result that is 99 +/- 10 percent of the general relativistic prediction. The GP-B satellite is currently flying with 4 electrostatically suspended superconducting gyroscopes in order to make a more accurate and more direct measurement of this effect.

The Lyman Alpha Forest

19 Jul 2004 - Distant quasars show absorption lines due to intervening "clouds" of neutral hydrogen. The strongest absorption line of neutral hydrogen is Lyman alpha. There are a very large number of Lyman alpha absorption lines on the blue side of the quasar Lyman alpha emission line, because the absorbing clouds have to be between the quasar and us, and thus have a smaller redshift. The Lyman alpha forest lines correspond to very small scales in the Universe, typically a few million light years, while the cosmic microwave background (CMB) anisotropy corresponds to billions of light years. By comparing the density fluctuations on these widely separated scales Seljak et al. (2004) have derived a very precise value for the slope of the power spectrum of primordial density fluctuations, n = 0.98 +/- 0.02. The inflationary scenario predicts n = 1, or equal power on all scales. They also find that this slope is constant, with the change in slope per factor of e = 2.71828 in scale being only -0.003 +/- 0.010 which is consistent with zero.

Most Distant Object in Question

12 Jul 2004 - The object alleged to have a redshift of z=10, making it the most distant known object has been the subject of two contradictory papers recently. The first claims that the emission line used to measure the redshift is not present in the data, while the second paper is a reply by the original authors saying that it is present with the proper analysis. In any case this line looks unlike other high redshift Lyman alpha emission lines that have been seen, so the case for this object remains to be confirmed, preferably by finding other lines.

And another preprint claims that the object is not present at all.

Co-Inventor of the Steady State Passes

22 June 2004 - Thomas Gold, born in Austria, educated in England, a professor at Harvard and then Cornell, has died at the age of 84. He was one the three inventors of the Steady State model of the expanding Universe. He also identified radio pulsars as rotating magnetized neutron stars.

Hubble Ultradeep Field

9 March 2004 - The Hubble Space Telescope released its ultradeep field data and images at a press conference today. This story was covered on the front page of the New York Times, who sent their own reporter; and on the front page of the Los Angeles Times, who used the Associated Press wire service story. The Washington Post ran the AP story on page 12. This press event was defintely part of the fight over the future of the HST, with Senator Barbara Mikulski making an unannounced appearance at the unveiling. But it was also a significant scientific event, since the HST with its new Advanced Camera for Surveys (ACS) and its repaired infrared camera (NICMOS), is able to observe very distant galaxies with a long time exposure, and over a million seconds of observing time went into the HUDF. The first preprint reporting a scientific analysis of the HUDF data appeared on 10 March 2004.

Most Distant Object Record Smashed

1 Mar 2004 - Pello et al. have found a galaxy much further away from us than any previously known. The evidence comes from a single line observed in the infrared which imples a redshift of z = 10. The source is seen magnified by a cluster of galaxies, Abell 1935, acting as a gravitational lens, and the source location is where sources with 9 < z < 11 should be very highly magnified. The colors of the source are also very consistent with z = 10. The technical paper and the press release both give pictures and spectra of this object. My Cosmology Calculator gives for z = 10 and the WMAP cosmic parameters (Ho=71, OmegaM=0.27 in a flat Universe) an age of the Universe of 0.48 Gyr at the time the light we see was emitted, a light travel time of 13.18 Gyr, and a current distance of 31.5 billion light years. This distance is much greater than the speed of light times the light travel time because the Universe has expanded by factors between 1 and 1+z=11 since the light did its traveling.

Corrupted Echoes from the Big Bang? - Not!

2 Feb 2004 - A group led by Prof. Tom Shanks of the University of Durham, UK, has suggested that the Sunyaev-Zeldovich effect may have significantly affected the WMAP results on the anisotropy of the cosmic microwave background. However, the S-Z effect goes through zero at 220 GHz and the ARCHEOPS balloon-borne CMB experiment which observes at 143 and 217 GHz sees the same map and angular power spectrum as WMAP. The fact that ARCHEOPS agrees with WMAP within -4.4+/-2.8% in the amplitude of the first acoustic peak means that the S-Z effect has very little influence on the WMAP results. So this was another scientific theory that, like the dodecahedral Universe, was already disproven by the time the authors sent out their press release.

Variable Constants?

9 Jan 2004 - Chand et al. (2004) present data on the time variation of the fine structure constant alpha that contradict previous claimed detections of a variation. The latest result is -0.6+/-0.6 parts per million for the change which is consistent with zero and much more accurate than the claimed -7.2+/-1.8 variation. So this constant really is constant.

A Double Radio Pulsar

9 Jan 2004 - Lyne et al. (2004, Science in press) gives the details about PSR J0737-3039 A&B, the double radio pulsar binary with a relativistic orbit, previously reported as a single pulsar in a binary system on 4 Dec 2003. The mass of the 23 millisecond pulsar (A) is 1.337+/-0.005 M(sun) while the mass of the 2.8 second pulsar (B) is 1.250+/-0.005 M(sun). There are now 6 measured constraints on (MA,MB) and the values given above are consistent with all 6 constraints, providing a stringent test of General Relativity which GR passes with flying colors.

Science Magazine names "Illuminating the Dark Universe" as Breakthrough of the Year

19 Dec 2003 - With the Wilkinson Microwave Anisotropy Probe (WMAP) results on the most distant parts of the observable Universe, the Sloan Digital Sky Survey (SDSS) results on the large scale structure in the galaxy distribution "near" (within several billion light years) the Earth, and the confirmation of the correlation between the CMB anisotropy and the large scale structure produced by the late integrated Sachs-Wolfe effect by Boughn & Crittenden (2003); Nolta, Wright et al. (2003); Fosalba & Gaztanaga (2003) & Scranton et al. (2003) the evidence for a Universe dominated by a "dark energy" is now quite strong. This dark energy, or "smooth tension" in Sean Carroll's words because it is unclustered and has negative pressure, was first seen in accelerating expansion of the Universe found using supernovae. The accelerating expansion of the Universe was the Science Magazine Breakthrough of the Year for 1998.

SIRTF renamed Spitzer Space Telecope, First Results Released.

18 Dec 2003 - The Space Infrared Telescope Facility (SIRTF) has been renamed for Lyman Spitzer, a pioneer in putting telescopes in space. Back when the HST was the Large Space Telescope at 3 meter diameter we always read the LST acronym as the Lyman Spitzer Telescope. The Spitzer Space Telescope's first images show star forming regions in our galaxy, cold dust orbiting nearby stars, and comets and asteroids. By following the light from the common cool stars into the infrared in distant redshifted galaxies, the SST will provide excellent data for cosmology.

An amazing binary pulsar

4 Dec 03 - Nature today published a paper (Burgay et al. 2003, Nature, 426, 531-533) about a newly announced millisecond pulsar, PSR J0737-3039, in a relativistic binary system. Radio pulsars are neutron stars (NS) which have a mass of about 1.4 solar masses and a radius of 10 km, magnetic fields billions to trillions of times larger than the Earth's magnetic field, and spin periods from 1.6 milliseconds to several seconds. PSR J0737-3039 is orbiting another neutron star every 2.4 hours and the two stars will merge in 85 Myr due to gravitational radiation. Hence LIGO will have many more detectable NS+NS merger events based on the statistics of two objects instead of the previous estimate based solely on the one merging binary pulsar PSR B1913+16 known earlier.

There is currently a program on the GBT radiotelescope schedule entitled "RRS Observations of the Double Binary Pulsar PSR J0737-3039" indicating that this is more than just a pulsar in orbit around a neutron star. And there is a Director's Discretionary Time Chandra observing proposal that says that both neutron stars in this system are pulsars, the previously announced pulsar with 22 millisecond period and a 2.7 second period for the companion. The millisecond pulsar (A) is eclipsed for 22 seconds as it passes behind the slow pulsar (the B component). Since the relative motion of the two stars is 14,000 km in 22 seconds, this eclipse must be caused by a wind coming from the B component instead of the disk of the neutron star which is tiny.

The program for the 12-16 Jan 2004 Aspen Winter Conference on Astrophysics has a paper by Manchester about eclipses in PSR J0737-3039 and another paper by McLaughlin on another relativistic binary pulsar PSR J1849+24. This should be an interesting meeting.

A twelve-sided Universe? - Probably not.

9 Oct 2003 - Luminet et al., (2003, Nature, 425, 593-595) suggest that the Universe has a small topology, and what looks like a finite spherical Universe is really made up of 120 images of a single dodecahedron. Under this hypothesis, the whole Universe is slightly smaller than the observable sphere bounded by our surface of last scattering. But when our line of sight leaves the dodecahedron, it comes back in on the opposite face. Thus we would not see any sharp edge between the inside and outside of the dodecahedron, but we could see some parts of the surface of last scattering more than once from different directions, just as we can see many images of a barber in a traditional barber shop with mirrors on both the front and back walls. As a result, there should be circles on opposite sides of the sky where the cosmic microwave background anisotropy matches up. In fact, there should be six pairs of such circles. But Luminet et al. did not look for these circles in the WMAP anisotropy data before publishing in a Nature cover story. The negative results of such a circle search are given by Cornish et al. Thus this theory is discussed under the headline "Cosmic Soccer Ball? Theory Already Takes Sharp Kicks" in today's New York Times.

Precision Test of General Relativity

25 Sep 2003 - Bertotti, Iess & Tortora (2003, Nature, 425, 374-376) report a precision test of the Shapiro time delay using radio tracking of the Cassini spacecraft going to Saturn. This effect is equivalent to the bending of starlight. Einstein predicted that starlight would be deflected by twice as much as the Newtonian prediction. This latest measurement implies a deflection by 2.000021+/-0.000023 times the Newtonian deflection which is a very precise test of general relativity. A strictly Newtonian calculation with light as bullets traveling at c actually gives a negative delay - a speedup. This error also occurs for a strictly Newtonian calculation of refraction by glass.

GR is at the heart of modern cosmological models.

SIRTF Launched!

25 Aug 2003 - The Space InfraRed Telescope Facility (SIRTF) was launched today at 01:35 AM EDT from the Cape Canaveral Air Force Station in Florida. This is the last of the "Great Observatories" that includes the Hubble Space Telescope (1990-now), the Compton Gamma Ray Observatory (1991-2000), and the Chandra X-ray Observatory (1999-now). SIRTF will be orders of magnitude more sensitive than previous facilities in the thermal infrared wavelength region: 3.5 to 160 microns. Click on the artist's conception of SIRTF in it's Earth trailing heliocentric orbit at right for an infrared view of the launch.

How many stars in the Universe?

22 Jul 2003 - Australian astronomers got a lot of press coverage for their simple calculation that there are 70,000,000,000,000,000,000,000 stars in the observable Universe. My own calculation in a 6 May 2003 response to a reader's E-mailed question was

Q: about how many stars are there. a rough estimate will be fine. LOL?
A: more than 100,000,000,000,000,000,000,000
Of course that's just the observable Universe, and the whole Universe is much bigger and perhaps infinite.

Many, many supernovae

1 May 2003 - Tonry et al. (2003) have published data on 230 supernovae. 170 of these are from their own Hi-z Supernova Team, while another 60 are from the Supernova Cosmology Project. My fit to these data prefers a closed accelerating Universe, but when combined with the CMB data, the best fit is a flat accelerating Universe. My supernova cosmology page has updated fits and plots.

MAP Data Released!

11 Feb 2003 - The results from the first year of observing by the Wilkinson Microwave Anisotropy Probe were announced today at a Space Science Update in the auditorium of NASA HQ. Important results include:


Speed of Gravity

7 Jan 2003 - Kopeikin and Fomalont claim to have measured the speed of gravity by observing the deflection of radio waves from a quasar by the gravity of Jupiter. They found that the speed of gravity was equal to the speed of light, as predicted by general relativity. Cliff Will disputes this claim, stating that the deflection does not depend on the speed of gravity. But nobody disputes the fact that Kopeikin and Fomalont's data agree with general relativity. The only dispute is over what a theory with the speed of gravity different than the speed of light would predict.

Highest Redshift Quasar, z = 6.4

23 Oct 2002 - In Bob Becker's talk at UCLA today, he showed spectra of a quasar with redshift z=6.4 from the SDSS. This second line of sight confirms the existence of a Gunn-Peterson trough in the spectrum due to neutral hydrogen at z > 6.

MOND is Dead? ...maybe

22 Oct 2002 - The Chandra X-ray Observatory presented evidence against the MOdification of Newtonian Dynamics (MOND) alternative to dark matter theories. The August 2002 Scientific American has a long article about MOND. The hot X-ray emitting gas around the galaxy NGC 720 forms an ellipsoidal cloud, which requires an ellipsoidal gravitational potential well. While an ellipsoidal cloud of dark matter could provide such a well, MOND would necessarily give a spherical potential well. In general MOND works well on the scale of individual galaxies, but not for clusters of galaxies. So why is MOND only maybe dead? Its supporters like Milgrom are persistent and clever, and they may come up with a MONDian explanation for NGC 720.

French Balloon Experiment ARCHEOPS Measures CMB Anisotropy

9 Oct 2002 - The ARCHEOPS experiment, which is a balloon-borne testbed for the European Space Agency PLANCK mission, announced results today. Based on the typical size of hot and cold spots in the 2.73 K radiation left over from the Big Bang, they confirm that the Universe is spatially flat. Two preprints by Benoit et al. describe the measurements and the resulting cosmological constraints.

Expected CMB Polarization Detected

19 Sep 2002 - John Carlstrom announced today the discovery of polarization in the CMB anisotropy. The data were taken with DASI, the Degree Angular Scale Interferometer. These results show the expected pattern of polarization produced by electron scattering at the time when the Universe recombined and became transparent, a half million years after the Big Bang. The thumbnail at right is a link to a page of high resolution images for the press, while this is an image from the polarization page for experts. The little polarization lines in these figures tend to line up circling around hot spots in the CMB anisotropy and to line up pointing in and out toward cold spots. Technical papers by Kovac et al. and Leitch et al. describe this result in more detail.

CMB Pioneer Passes

5 Sep 2002 - David T. Wilkinson, emeritus professor of physics at Princeton, died this evening after a long battle with cancer. Wilkinson was one of the recipients of Bob Dicke's comment: "Boys, we've been scooped" when the Penzias and Wilson discovery of the CMB was announced. Wilkinson made many pioneering measurements of the spectrum of the CMB, the anisotropy of the CMB, and the extragalactic background light during a distinguished career at Princeton. He was one of the leaders of the COBE proposal and COBE science working group, and of the currently operating MAP spacecraft.

MAP's Birthday

30 Jun 2002 - The Microwave Anisotropy Probe, or MAP, has been in space for 1 full year. It has been orbiting around the L2 point in the Earth-Sun system for the last nine months. During that time it has mapped the cosmic microwave background (CMB) sky in 5 frequencies from 22 to 94 GHz over 100.000% of the sky, and is now working on its second coverage. The thumbnail at right shows the track of MAP on the sky relative to the point opposite the Sun in the sky. Click on it for a larger version.

Cosmic Microwave Background Anisotropy

23 May 2002 - The Very Small Array (VSA) and the Cosmic Background Imager (CBI) both released new high angular resolution data on the minute temperature differences around the sky in the 2.725 K blackbody radiation left over from the Big Bang. The 24 May 2002 New York Times reported the CBI results under the headline: "Scientists Develop the Universe's Baby Pictures" which is a pretty good description of these results. [ CNN coverage of CBI, BBC coverage of VSA,VSA on the Astronomy Picture of the Day].

Old Dwarfs give Age of the Universe

24 Apr 2002 - The Hubble Space Telescope has measured the ages of white dwarfs in the globular cluster M4. The oldest white dwarfs are 12.7 +/- 0.7 billion years old in this cluster, so the Universe is 13-14 billion years old. The technical paper by Brad Hansen of UCLA and others is available here.

Strange Matter?

10 Apr 2002 - The NASA Space Science Update on 10 April 2002 described evidence for strange quark stars from the Chandra X-ray Observatory. This evidence has two parts: (1) the X-ray source RXJ1856 appears to have a radius smaller than the smallest allowed radius for a neutron star [preprint], and (2) the 65 ms pulsar in the supernova remnant 3C58 which coincides with the historical SN 1181 appears to be too cool for its age [preprint]. Neither of these is proof positive for the existence of strange quarks stars. But if strange quark stars do exist, then the possible existence of small stable bits of strange quark matter called strangelets could explain the dark matter. Caveats: the distance of RXJ1856 factors directly into its radius, and distances are very hard to measure in astronomy, and the cooling curves of neutron stars are rather uncertain. And other interpretations of the X-ray spectrum of RXJ1856 give much larger radii fully consistent with neutron star models.

Also, an illustration in the press kit gives the diameter of RXJ1856 as 12 miles = 19.2 km, while NASA press release 02-65 gives a diameter of seven miles = 11.3 km.

MAP wins Popular Science Poll

4 Jan 2002 - MAP [Microwave Anisotropy Probe] won the "Best of What's New" for 2001 poll in Popular Science.

MAP halfway to full sky coverage

1 Jan 2002 - MAP has covered 75% of the sky in the three months it has been at L2, including all of the 3% of the sky coveraged by BOOMERanG and all the sky covered by DASI. Sky coverage will continue at a slower pace until MAP will have covered 100% of the sky after 6 months at L2.

MAP reaches L2

1 Oct 2001 - MAP has officially reached its observing station at L2, a point 1.5 million km further from the Sun than the Earth, but on the Earth-Sun line. Over the next 6 months MAP will make a map of the whole sky in 5 microwave bands, studying minute temperature variations in the 2.725 K radiation left over from the Big Bang, and giving new insights into the nature of the Universe.

Fred Hoyle Dead at 86

20 Aug 2001 - Fred Hoyle, co-creator of the Steady State cosmological model, has died. He coined the phrase "Big Bang" model for what is now the most generally accepted cosmological model, in which the entire Universe was created at some finite time in the past. In the Steady State model, on the other hand, matter is continuously created to maintain a constant density by counteracting the dilution of matter by the expansion of the Universe. The Steady State model was arguably the best fit to the available observations prior to discovery of the cosmic microwave background in 1965. [New York Times obituary]

Variable Constants?

click for larger version 15 Aug 2001 - USA Today reports on a paper that claims to have seen a variation in the fine structure constant, alpha. Since one of the factors in this dimensionless ratio [=1/137.036...] is the speed of light, USA Today headlined the idea that the speed of light might have varied. Coverage on the first page of the Week in Review section of the 19 Aug 2001 New York Times was more restrained. But John Bahcall of the IAS is cautious about this result, and I also urge caution because of several factors:

Edge of Darkness?

4 Aug 2001 - Today's New York Times has a first page story indicating that the SDSS has seen the smooth distribution of neutral hydrogen expected in the Universe between the time the hot plasma from the Big Bang became neutral at redshift close to 1000 and the time after quasars formed and reionized the intergalactic gas. This neutral gas was seen in the spectrum of the most distant known quasar, J1030+0524, at z = 6.28. Fan et al. (2001, AJ, submitted) and Becker et al. (2001, AJ, submitted) are papers describing these results.

MAP Launched!

30 Jun 2001 - The Microwave Anisotropy Probe was successfully launched and is now in the first of its phasing loops with the solar panels extended, attitude under control, instrument on. [Pictures]

Cosmic Microwave Background Anisotropy

29 Apr 2001 - DASI announced results today at the APS meeting showing that the second peak of the CMB angular power spectrum had the amplitude expected from theoretical models of the Big Bang. This was reported on the front page of the New York Times for 30 Apr 2001. Preprints are available on XXX for DASI, and for BOOMERanG and MAXIMA who also announced new analyses of previously published data today. I have prepared a graphical comparison of the results announced today to the results announced in April-May 2000.

Expansion of the Universe Confirmed

25 Apr 2001 - Goldhaber et al (2001, ApJ in press) have analyzed observations of 60 supernovae at various redshifts and find that the width or duration of the light curve is proportional to (1+z) where z is the redshift. This is just what is predicted in expanding Universe models and contrary to the prediction of tired light models.

Most Distant Object

23 Apr 2001 - SDSS has found a redshift 6.28 quasar. SDSS1030 has a flux of about 45 microJy at a wavelength of 0.95 micron. This is slightly further away than z=6 quasar of last week and the two SDSS quasars at redshift z = 5.8.

16 Apr 2001 - SDSS has found a redshift 6.0 quasar. SDSS1306 has a flux of about 60 microJy at a wavelength of 0.9 micron. This is slightly further away than the two SDSS quasars at redshift z = 5.8.

Most Distant Supernova

2 Apr 2001 - The HST announced the results of a study of the most distant known supernova [SN 1997ff] today. The redshift of this supernova is about 1.7, based on a photometric redshift of the host galaxy [z = 1.65+/-0.15], a photometric redshift of the supernova [z = 1.7+/-0.15], and a tentative spectroscopic redshift of z = 1.755 for the host galaxy. It was discovered by Gilliland et al. (1999) in pictures of the Hubble Deep Field taken in 1997. No spectra of this supernova were taken while it was "bright" [the peak observed brightness was 27th magnitude at a wavelength of 0.8 microns], but the redshift of its host galaxy is known. The new results today involve the use of many images from the HST archive that covered the Hubble Deep Field and showed this supernova. Analysis of these images allowed one to construct the lightcurve of the supernova and thus estimate its intrinsic luminosity. Given the intrinsic brightness of this supernova, its observed brightness is not particularly faint compared to previously known supernovae with redshifts close to 1, which indicates that the expansion of the Universe had not started to accelerate at redshift 1.7. This behavior is consistent with cosmological models having a cosmological constant or dark energy. To be specific, the supernova is about 0 to 1 magnitude brighter than it would be in an empty Universe with Omega=0, while earlier supernovae at redshifts near 0.5 were dimmer than they would be in an empty Universe. The graph at the right shows the decelerating model which has no dark energy in black, and an accelerating model with dark energy in purple. A proposed alternative to dark energy is a model which makes the distant supernovae faint by adding absorbing dust between the galaxies, and is shown as a black dashed curve. The old data could not distinguish between the dashed and purple curves, but the new data can. These points were measured off of Figure 12 of Riess et al. (2001, ApJ in press). The empty Universe model, shown in green, is the boundary between decelerating and accelerating models. Other models shown are a closed model (OmegaM = 2) in red and a pure vacuum dominated model (Omegavac = 1) in blue. For Ho=70, OmegaM = 0.3 and Omegavac = 1-OmegaM = 0.70, the age of the Universe is 13.5 Gyr, the light travel time since z = 1.7 is 9.7 Gyr, the current distance of the supernova is 15.4 billion lightyears, and the luminosity distance, which is the only distance actually measured to this object, is 41.5 billion lightyears. These values were computed using my Cosmology Calculator.

A Dark Halo of White Dwarfs?

2 Apr 2001 - Richer withdraws the claimed detection of faint, high proper motion stars in the Hubble Deep Field. This reduces the support for the claim by Oppenheimer et al. for white dwarfs in a dark spherical halo but the volume surveyed in the HDF is too small for a definitive test. Also Reid, Sahu & Hawley (2001) note that the velocity distribution of these objects is more like a thick disk than a halo distribution.

23 Mar 2001 - Oppenheimer et al. claim in Science that 3% of the halo mass in the Milky Way is formed from old faint white dwarfs. You can find the Oppenheimer et al. paper here along with their discussion of the Reid et al. paper.

New Age of the Universe

7 Feb 2001 - Another very old star has given an age for the Universe: more than 12.5 +/- 3 billion years. This measurement is based on the decay of U-238 in the star.

Scientific American Features Cosmology

Jan 2001 - This month's Scientific American includes this report card on cosmological results from Princeton physics professor Jim Peebles.

Evolution of the Universe Confirmed

21 Dec 2000 - Today's Nature contains an article by Srianand, Petitjean & Ledoux (2000, Nature, 408, 931) which confirms the evolution of the Universe from a hotter denser state to its present condition. This confirms one of the tenets of the Big Bang.

Faster than light? - No!

20 Jul 2000 - Today's Nature has an article Wang, Kuzmich & Dogariu (2000, Nature, 406, 277) reporting on "superluminal" propagation, but it is just anomalous dispersion. The media are fooled again!

Cosmic Microwave Background Anisotropy

9 May 2000 - Hanany et al. announce results of the August 98 flight of the MAXIMA experiment which are generally in agreement with the BOOMERanG results below, but without any tendency to favor a slightly closed Universe. My CMB angular power spectrum graphs have been updated to include MAXIMA.

27 Apr 2000 - Today's Nature has an article reporting the results from the 10 day long duration balloon flight of the BOOMERanG project. These measurements of very small CMB temperature fluctuations over 1% of the sky with a beam size 40 times smaller than COBE's 7o beam confirm earlier work by a group at Penn & Princeton and data from BOOMERanG's test flight, but provide 3 to 4 times more accuracy. Based on this data, de Bernardis et al. (2000, Nature, 404, 955) conclude that the Universe is flat.

The angular size of the characteristics spots on the sky, about 1o, shows that the Universe is flat, or that the total energy density is equal to the critical density. This confirms a prediction of the inflationary scenario. The amplitude of the characteristics spots, about 69 microK, indicates the ratio of ordinary matter (baryonic matter) to dark matter. Detailed studies of the harmonics or overtones of the fundamental oscillations that lead to these spots will provide much more information about the Universe. Stay tuned.

The New York Times, the Los Angeles Times, and the Washington Post all covered this story extensively.

The first of what will certainly be many interpretations of the BOOMERanG data by outside groups was posted to the LANL preprint server on the same day the Nature paper came out by White, Scott & Pierpaoli.

Sloan Digital Sky Survey finds z=5.82 Quasar

13 Apr 2000 - SDSS announced a quasar with a redshift of z = 5.82. Of course, the press release called it the "Most Distant Object Ever Observed" which discounts the z = 6.68 galaxy. [ Stern et al. (2000, Nature, 408, 562) disagree with the z=6.68 for this object.] However, the spectrum of the SDSS object taken by Fan, White, Davis, Becker et al. at the Keck Observatory is much better than the noisy spectrum of the extremely faint z=6.68 object. Notice the very strong and wide Lyman alpha line of hydrogen, redshifted from 122 nm to 829 nm wavelength. The blue side of the line has been absorbed in the Lyman alpha forest.

New Most Distant Quasar

18 Feb 2000 - Daniel Stern et al. announce the discovery of the most distant known quasar, with a redshift of z = 5.5. The previous record holder has a redshift of z = 5.0.

Cosmic Microwave Background Anisotropy

26 Nov 99 - The New York Times had a front page story about new CMB temperature fluctuation data released by the BOOMERanG project. Based on this data, which confirms earlier work by a group at Penn & Princeton, they conclude the Universe is flat.

Cosmic Near Infrared Backgound

27 Sep 99 - Gorjian, Wright(*) & Chary have found an extragalactic IR background of 22.4 +/- 6.0 nW/m2/sr at 2.2 microns and 11.0 +/- 3.3 nW/m2/sr at 3.5 microns. This result completes the primary goals of the COBE mission.
(*) - that's me.

And then on 27 Dec 99 Wright & Reese confirmed the cosmic IR background (CIRB) obtaining 23.1 +/- 5.9 nW/m2/sr at 2.2 microns and 12.4 +\- 3.2 nW/m2/sr at 3.5 microns.

Mystery Object! - NY Times publishes a SPECTRUM!!

21 Aug 99 - The "mystery object", PSS 1537+1227, found on the Digital Palomar Observatory Sky Survey (DPOSS) by Djorgovski et al. has been identified as a Broad Absorption Line quasar (BAL QSO) with a redshift of 1.2. The spectrum of the mystery object shown at right is very similar to the spectrum of the radio-loud BAL QSO 0840+3633 discussed by Becker et al. (1997), redshifted to z = 1.19.

But the most amazing part of this story is that the NY Times published a spectrum in the 17 Aug 99 print edition - a clear violation of the "5 W's but no Z" rule that I think must be taught in science journalism schools. The graph at right is a plot of the flux received from the mystery object in microJanskies vs. the wavelength of the light in nanometers.

Since spectroscopy is the tool most used by astronomers today, this article in the NY times was very significant. Spectra tell astronomers what elements are in distant stars and galaxies, how hot and dense these objects are, and how rapidly they are moving towards us or away from us.


A Warning Label for Supernovae

2 Jul 99 - Riess et al. report that distant, high redshift supernovae have significantly shorter rise times than the nearby supernovae used to calibrate the luminosity vs. decay time relationship. This is an indication of some kind of evolution in the supernova population, and if this evolution also affects the peak luminosity for a given decay rate it will directly affect the cosmological conclusions drawn from distant supernovae.

New Most Distant Galaxy

15 Apr 99 - Chen, Lanzetta & Pascarelle report a galaxy with redshift z = 6.68. The galaxy is indicated by the tickmark on the 2.3" by 22" image shown above, taken with the STIS instrument on the HST. This report is based on a single emission line at 933.4 nm which they identify with the Lyman alpha emission line of hydrogen, which is emitted with a wavelength of 121.5 nm. The spectrum taken with STIS in the slitless mode is shown at right. There is also a break in the continuum at 930 nm which they identify with the Lyman alpha forest. The blue curve shows the smoothed spectrum which follows the continuum. This is a more detailed article about the galaxy reported earlier on 24 Sep 98, and it appears in today's Nature.

Stupendous Gamma Ray Burst

26 Mar 99 - Nature has articles about the gamma-ray burst GRB990123 which was captured "live" by the Robotic Optical Transient Search Experiment (ROTSE) instrument reaching 9th magnitude in the optical, has a redshift > 1.6, and which had a gamma-ray fluence of 0.0003 erg/cm2. For Ho = 65 km/sec/Mpc, matter density OmegaM = 0.25 and cosmological constant lambda = 0.75, the luminosity distance of this source is 43 billion lightyears. [The value 9 billion light years reported in the newspapers seems to be some useless value like the light-travel distance.] The total energy released in the burst is

E = fluence*4*pi*DL2/(1+z) = 2.4*1054 ergs
which corresponds to the total annihilation and conversion into gamma rays of 1.35 solar masses of matter.

Galaxies at z > 10?

18 Dec 98 - Chen et al. report photometric redshifts for galaxies in the Hubble Deep Field South, including one galaxy with z = 10.56! This requires confirmation and followup, of course. The galaxy is so faint that spectroscopy will have to wait for the Next Generation Space Telescope.

A New Quasar Distance Record

11 Dec 98 - The Sloan Digital Sky Survey has found several new quasars with redshifts greater than 4.9 in a tiny fraction of their planned survey area. The old quasar distance record was a redshift of 4.897. The spectrum of the new quasar with redshift z = 5.0, seen at right, has three obvious emission lines so the line identification is secure and thus the redshift is reliable. Currently the most distant known objects are galaxies, including one with a redshift of 6.68.

Redshift Record falls Again

24 Sep 98 - Lanzetta et al. report an object with a spectroscopic redshift of z = 6.68, based on only one emission line at 930 nm, assumed to be the Lyman alpha line, with a jump in the continuum at the line. This is the most distant known object, but confirmation of the distance will require spectroscopic observations in the infrared, which may be possible in 1999 using the NIRSPEC instrument on the Keck telescopes.

A Chill in the Air

28 Aug 98 - Mather et al. (1998, ApJ in press), "Calibrator Design for the COBE FIRAS", give a slightly reduced value for the CMB temperature, To = 2.725 +/- 0.002 K, with 95% confidence. This important cosmological observable is now known to better than one part per thousand.

Infrared Selected Most Distant Object

20 Jul 98 - A galaxy in the Hubble Deep Field which is very faint in the visible but relatively "bright" in the IR has an emission line at 803 nm, identified as Lyman alpha at z = 5.60.

Neutrinos have mass

5 Jun 98 - The Super-Kamiokande experiment released a press release tied to a presentation at the Neutrino'98 meeting, which announced that Super-K had confirmed that muon neutrinos produced in the Earth's atmosphere by cosmic rays were changing ("oscillating") into a different kind of neutrino during their passage through the Earth. It is an interesting commentary on science journalism that this press release generated front page headlines, while an article in the 29 May 98 Science by Joel Primack (v 280, pp 1398-1400), which states exactly the same properties of neutrinos based on preprints available at xxx.lanl.gov, did not.

The oscillation data do not determine the masses of neutrinos, but rather the difference between the squared masses of two neutrino types. The atmospheric muon data gives m22 - m12 = 0.001 to 0.01 eV2. Since the sum of the three neutrino masses has to be 5 to 7 eV to be cosmologically interesting, this result from Super-K is a mixed blessing for Mixed Dark Matter models, since is shows that

One way out of this difficulty is to introduce a fourth neutrino type, a sterile neutrino. But this abandons one of the best aspects as neutrinos as dark matter: that the particles have actually been seen.

A Most Powerful Gamma Ray Burst

7 May 98 - GRB 971214 came from a galaxy with redshift z = 3.42 according to Kulkarni et al. (1998, Nature, 393, 35). This source was seen by BeppoSAX as a gamma ray burst and as a fading X-ray transient, and the fading optical transient was seen by observatories around the world. The BATSE gamma-ray fluence for this trigger (#6533) is 1.1*10-5 erg/cm2, and with H0 = 50 km/sec/Mpc and Omega = 1 this requires a gamma-ray emission in the source of 2.3*1053 ergs. This is about the same as the neutrino emission from a Type II supernova but it all has to come out as gamma-rays.

A Bull Market

9 Apr 98 - Yahoo reports bigger than expected profits. Given the sorry state of its cosmology listings, one has to ask why?

A New Most Distant Object: z = 5.34

12 Mar 98 - Dey et al. report a galaxy at redshift z = 5.34 based on a single line in the spectrum at 771.7 nm wavelength which they assume is Lyman alpha. Even though this is based on only one line, the line profile and continuum dropoff on the blue side look very much like Lyman alpha lines in other high redshift objects. Esther Hu et al claim an object at z = 5.64 but the spectrum is much weaker because of the strong night sky emission.

ANTI-GRAVITY? - Report on DM98

4 Mar 98 - Results reported at the DM98 meeting sponsored by UCLA are coming out in the popular press: the 3 Mar 98 New York Times and the 27 Feb 98 issue of Science (1998, 279, 1298). These stories both cover the High-Z SN Team results on distant supernovae, which are in accordance with the LBL results reported below for 6 Feb 98. Both groups support a non-zero cosmological constant, a term Einstein added to general relativity which allows a static Universe because it gives a repulsive gravity.
More about the cosmological constant.
Redshift-distance plot of the distant supernovae, and a plot showing the error ellipses of the two groups.

More on Distant Supernovae

6 Feb 98 - The 30 Jan 98 issue of Science (1998, 279, 651-652) has a News article with a graph from the LBL (Perlmutter) group with many more SNe included, which indicates that OmegaM - 0.863*lambda = -0.40 +/- 0.15(stat) +/- 0.81(sys) and 0.863*OmegaM + lambda = 0.97 +/- 1.92. A more detailed write-up gives 0.8*OmegaM - 0.6*lambda = -0.2 +/- 0.1 (stat), and OmegaM = 0.28+0.09-0.08 for a flat OmegaM + lambda = 1 model. The potential systematic errors could be large, but this is good evidence for a non-zero lambda (cosmological constant). [The High-z SN Team results (see 4 Mar 98 above) can be written as OmegaM - 0.823*lambda = -0.31 +/- 0.14 and 0.823*OmegaM + lambda = 0.95 +/- 1.92 which are remarkably similar to the LBL results.]

Far Infrared Background Radiation

9 Jan 98 - The DIRBE (Diffuse InfraRed Background Experiment) team on the COBE satellite announce that they have detected a Far InfraRed Background (FIRB) at 140 and 240 micron wavelengths.
Images of the sky before and after foreground removal are on the Astronomy Picture of the Day Web site.
This FIRB is very small: if you put an IR detector in your refrigerator, and closed the door so the light went out, the detector would still see 7 billion times more power than the far IR background.
Five papers: Hauser et al. giving the FIRB conclusions, Kelsall et al. describing the zodiacal light foreground removal, Arendt et al. describing the galactic foreground removal, Dwek et al. giving a theoretical interpretation, and Fixsen et al. comparing the FIRAS data to the DIRBE data have been submitted to The Astrophysical Journal. Previously posted or published papers by Schlegel, Finkbeiner & Davis (1998) found a similar FIRB using DIRBE data, and by Puget et al. (1996, A&A, 308, 5) found a similar background level using FIRAS data.
The detections reported by Hauser et al. are 25.0 +/- 6.9 nW/m2/sr at 140 microns and 13.6 +/- 2.5 nW/m2/sr at 240 microns. Fixsen et al. give 14 nW/m2/sr for the total intensity longer than 125 microns. These values are 1-2% of the Cosmic Microwave Background (CMB) radiation (the 2.725 K blackbody). In the S10 notation often used for sky brightness, 14 nW/m2/sr is about 1.4 mbol=10th magnitude stars per square degree.

More Distant Supernovae

16 Dec 97 - Perlmutter et al.(1998, Nature, 391, 51-54) get data on a supernova at z = 0.83. It shows a time dilation factor of 1.86+0.31-0.09 compared to the expected 1+z = 1.83, and agrees with Garnavich et al. (1998, ApJL, 493, L53-L57) that the density is less than the critical density, with Omega = 0.2 +/- 0.4 for no cosmological constant. This new point has been added to my large redshift magnitude-redshift diagram.

Millenium?

6 Nov 97 - This is the 6000'th birthday of the Universe, according to the Archbishop Ussher.

Gamma Ray Bursts are Cosmological

13 May 97 - GRB970508 has an associated optical transient source that shows absorption lines with a redshift of z = 0.835. From the absence of the Lyman alpha forest it is likely that the object itself is at z < 2.1, and it must have z > 0.835. Somehow the LA Times 15 May 1997 story converted these redshifts into distances between 2 and 7 billion light years. They must have been using Hubble's original value for Ho.

So we welcome a new class of objects to the field of cosmology. And we still don't know how to radiate 1051 ergs of gamma rays in a few seconds. This energy is all the energy the Sun will radiate in its entire 10 billion year lifetime.

Does the Universe Have an Axis? -

NO!

18 Apr 97 - Nodland and Ralston claim an intrinsic rotation rate for polarized light that varies with the cosine of the angle relative to a preferred axis. But Eisenstein and Bunn point out statistical flaws in Nodland and Ralston's work. I have found that using Eisenstein and Bunn's null hypothesis increases the probability of producing Nodland and Ralston's result by pure chance by more than a factor of 100(!) for the case where the axis is specified, and a factor of 60 when the axis is found from the data. As a result, the probability of getting the Nodland and Ralston work by chance is 30 percent, which means that their result is not statistically significant. Carroll and Field have done similar calculations and also find that there is no detectable intrinsic rotation. Leahy has made detailed studies of sources where the polarization angle can be predicted accurately, and finds that any rotation is at least 30 times smaller than that predicted by Nodland and Ralston. Even though the effect is clearly not present, Professor J. W. Moffat and net-kooks Ray Tomes and Archimedes Plutonium have each announced that the anisotropic rotation supports their theories.

A Galaxy Far, Far Away

10 Apr 97 - Most distant object record broken! Redshift z = 4.92 (Franx et al.)

It's earlier than you think.

10 Apr 97 - HIPPARCOS parallax data on subdwarfs puts globular cluster further away -- their stars more luminous and younger. (Reid)

1997 - HIPPARCOS Cepheid parallaxes increase distance scale by ten percent (Feast & Catchpole, 1997, MNRAS, in press)

1994 - Wendy Freedman et al. (1994, Nature, 371, 757-762) announce Ho = 80 +/- 17 km/sec/Mpc based on HST observations of Cepheids in the Viro Cluster, producing a major flap over "the Universe is younger than the oldest stars". But the Universe has gotten older and the oldest stars have gotten younger since then.

1992 - Smoot et al. (1992, ApJL, 396, L1) announce the discovery of intrinsic anisotropy of the microwave background. See Bennett et al. (1996, ApJL, 464,L1) for a summary of the final COBE DMR results.

1990 - Mather et al. (1990, ApJL, 354, L37) show microwave background spectrum is within 1% of a blackbody. Later Fixsen et al. (1996, ApJ, 473, 576) show that it is within 0.005% (RMS) of a 2.728 K blackbody.

1969 - Conklin (1969, Nature, 222, 971) discovers the dipole anisotropy in the microwave background. This was confirmed by Henry (1971, Nature, 231, 516) and reconfirmed by Corey & Wilkinson (1976, BAAS, 8, 351) before the first flight of the U-2 experiment, so it is clear that Smoot, Gorenstein & Muller (1977, PRL, 39, 898) did not discover the dipole, but they did make a good measurement of it.

1965 - Penzias & Wilson discover the microwave background: "A Measurement of Excess Antenna Temperature at 4080 Mc/s" (1965, ApJ, 142, 419).

1948 - Alpher & Herman (1948, Nature, 162, 774) predict T = 5 K for Universe.

1941 - Adams (1941, ApJ, 93, 11) reports on the CN R(1) line - first evidence of microwave background.

1933 - Zwicky finds that 90% or more of the matter in clusters of galaxies is dark.

1929 - Zwicky (1929, PNAS, 15, 773) proposes the tired light model for the redshift. However, the tired light model does not agree with current data.

1929 - Hubble discovers the expanding Universe: "A Relation between Distance and Radial Velocity among Extragalactic Nebulae" (1929, PNAS, 15, 168).

1927 - Le Maitre discovers the expanding Universe and derives a Hubble constant of 625 km/sec/Mpc. He gets little credit for this first derivation of the "Hubble" constant because he published his paper [PDF] in French in the Annales de la Societe Scientifique de Bruxelles.

1922 - Alexander Friedmann finds solutions of General Relativity representing homogeneous isotropic Universes expanding from a singularity - the Big Bang models.

1917 - de Sitter (1917, MNRAS, 78, 3) constructs a cosmological model which shows a redshift. [Now we usually change variables to put the de Sitter metric into the metric of the Steady State model with exponential expansion and flat spatial sections.]

1917 - Einstein models the Universe as a static homogeneous isotropic solution of General Relativity by introducing the cosmological constant.

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