Direction: Where did it
Gives you (X,Y) for a source, and potentially dX/dt, dY,dt, dX2/dt2,
The measurement of astronomical positions is called"astrometry"
Intensity: How many
photons are there?
Depends on both intrinsic luminosity and distance.
Measurement of intensities is"photometry"
Astronomers frequently measure flux on a logarithmic scale called the magnitude system.
M1-M2 = -2.5
Absolute fluxes can be specified
1 Jy = 10-26
W m-2 Hz-4
Energy(~ frequency ~ wavelength):
The analysis of astronomical spectra provides almost all of the
physical insight we have for astronomical objects. This is called
Different physics at different wavelengths. Factor of 109
between radio and gamma rays. Different physical processes involved in
production, different types of techniques needed for detection.
The broad shape of spectra indicates what sort of physical
process produced the light (thermal blackbody emission, synchrotron
emission, Brehmsstrahlung (free-free) emission, or line emission.)
Atomic and molecular lines provide information on
composition, chemistry, physical properties such as temperature and
Doppler shift provides radial velocities: dZ/dt
Astronomical colors function as a rough form of spectroscopy.
Filter systems are semi-standardized and include UBVRI
in visible, JHKLMN
in IR, and many others.
Polarimetry can provide information about physical processes including
scattering by dust, the presence of magnetic fields, and more, and can
be combined with spectroscopy to get spectropolarimetry.