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Cosmology and art |
New on the tutorial:
Cosmology is the study of the origin, current state, and future of our Universe. This field has been revolutionized by many discoveries made during the past century. My cosmology tutorial is an attempt to summarize these discoveries. It will be "under construction" for the foreseeable future as new discoveries are made. I will attempt to keep these pages up-to-date as a resource for the cosmology courses I teach at UCLA. The tutorial is completely non-commercial, but tax deductible donations to UCLA are always welcome.
Astronomy and cosmology are very much mathematical sciences, but I have attempted to avoid higher math in these pages. I do use high school algebra and geometry - courses required for admission to UCLA - but I have also included some animations [1, 2, 3, 4, 5, 6, 7], some Java applets [1, 2], and many illustrations in the tutorials, the ABC's of Distances, and the answers to some of the Frequently Asked Questions.
In addition to the cosmology tutorial, there is also a relativity tutorial and extensive discussions on the age, density and size of the Universe. There is also a bibliography of books at a range of levels, and a Javascript calculator of the many distances involved in cosmology.
Slides for recent talks:
The course notes (130 pages, 398 equations, 51 figures) for the upper division undergraduate Stellar Systems and Cosmology course, Astronomy 140, that I last taught in spring 2008 are available on the Web. And for a much more technical discussion of cosmology see my graduate course Astro 275 lecture notes (126 pages, 381 equations, 42 figures). This course was last taught in the spring of 2009. If this course Web site gets closed, you can use a backup copy of the A275 notes.
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.
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,
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.
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.
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.
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.]
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.
15 May 2009 - After 2090 days of crygenic 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.
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.
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.
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.
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.
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.
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.
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.
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.
FAQ | Tutorial : Part 1 | Part 2 | Part 3 | Part 4 | Age | Distances | Bibliography | Relativity
© 1996-2009 Edward L. Wright. Last modified 12 Nov 2009