This page grew out of my frustration at having to go away and look up (for the umpteenth time) Allen's indispensable "Astrophysical Quantities" to find out what the absolute magnitude of the Sun is. So here's a compilation of various things, as well as links to other reference sites.
The Sun
MV = +4.82
MB = +5.47
MU = +5.66
MR = +4.28
MI = +3.94
MK = +3.33
MM = +3.30
(From "Allen's Astrophysical Quantities", 4th edn., 2000 except MM
which is from the 3rd edn.)
Photometry
A magnitude of zero in each of the following bands corresponds to the flux density listed (from AQ, 4th edn., except the IR bands, which are from Koornneef 1983, A&A, 128, 84):
| Band | Flux (ergs/cm^2/s/Angstrom) |
|---|---|
| U | 4.22e-9 |
| B | 6.40e-9 |
| V | 3.75e-9 |
| R | 1.75e-9 |
| I | 8.4e-10 |
| J | 3.14e-10 |
| H | 1.2e-10 |
| K | 4.12e-11 |
| L | 6.41e-12 |
| M | 2.13e-12 |
Spectroscopy
| Line | Rest wavelength |
|---|---|
| [Fe II] | 1.257 microns |
| Pa-beta | 1.2822 microns |
| [Fe II] | 1.644 microns |
| Br-gamma | 2.1661 microns |
Radio Astronomy
Frequency of the neutral hydrogen hyperfine (spin-flip) transition = 1420.405752 MHz (from table 4.14 of AQ, 4th edn.)
HI mass (solar masses) = 2.356 x 105 * D2 * FI
where D is the distance in Mpc, and FI is the integral of flux over velocity (Jy km/s)
HI column density (projected):
M_HI (M_sun per pc^2) = 8.86 * FI / (a * b)
where a = major axis of beam (arcsec), b = minor axis of beam (arcsec), and FI is the integral of flux per beam over velocity (Jy/beam m/s).
or N_HI (10^20 per cm^2) = 11.08 * FI / (a * b)
Beam area = (Pi * a * b) / (4*ln(2)) = 1.133 * a * b
Formulae
FWHM = 2.35 * sigma for a Gaussian
Area of a Gaussian = sqrt(2 * Pi) * sigma * height = 1.067 * sigma * height
Miscellaneous
1 pc = 3.262 light years
1 pc = 3.086E16 m
1 pc = 206265 AU