astronomical contstants

Modified from C. Dolan's page

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Physical Constants

(in cgs)
Name Symbol Quantity
speed of light in a vacuum c 2.99792458x1010 cm s-1
Planck constant h 6.6260755(40)x10-27 erg s
hbar 1.05457266(63)x10-27 erg s
Gravitational constant G 6.67259(85)x10-8 dyn cm2 g-2 s-2 (in MKS, 10-11N m2kg-2)
Electron charge e 4.8032068(14)x10-10 esu
Mass of electron me 9.1093897(54)x10-28 g
Mass of proton mp 1.6726231(10)x10-24 g
Mass of neutron mn 1.6749286(10)x10-24 g
Mass of hydrogen mH 1.6733X10-24 g
Atomic mass unit amu 1.6605402(10)x10-24 g
Boltzmann constant k 1.380658(12)x10-16 erg k-1
Electron volt eV 1.6021772(50)x10-12 erg
Stefan-Boltzmann constant σ 5.67051(19)x10-5 erg cm-2 K-4 s-1
Fine structure constant α 7.29735308(33)x10-3

Astronomical Constants and Data

Name Symbol Quantity
Astronomical unit AU 1.49597870x1013 cm
Parsec pc 3.086x1018 cm=206265AU=3.26ly
Light year ly 9.463x1017 cm
Solar mass Mo 1.9891x1033 g
Solar luminosity Lo 3.9x1033 erg s-1
Jansky Jy 10-26 W m-2 Hz-1

A Few Conversion Factors

CGS --> SI Multiply by
centimeter (cm) meter (m) 10-2
gram (g) kilogram (kg) 10-3
erg Joule (J) 10-7
dyne (dyn) newton (N) 10-5
Other useful quantities:
dpcθarcsec=DAU

Sgr A*

For R=8kpc, 1"->8000AU=0.039pc
MBH=2.6x106Mo
Rs=2GM/c2=7.68x1011cm=0.05AU -> 6.4μas(R=8kpc)