Astronomy Principles and Practice Fourth Edition.pdf

456 Appendix: Astronomical and related constants
Derived SI units for special quantities
Physical quantity Name of unit Symbol Dimensions
energy joule J kg m 2 s −2
power watt W kg m 2 s −3
force newton N kg m s −2
electric charge coulomb C A s
magnetic flux density tesla T kg s −2 A −1
frequency hertz Hz s −1
Conversion of cgs units to SI units
1ångström = 10 −10 m
1 dyne = 10 −5 N
1erg = 10 −7 J
1 millibar = 10 2 Nm −2
1gauss = 10 4 T
1ergs −1 = 10 −7 W
SI prefixes
Factor Prefix Symbol Factor Prefix Symbol
10 −3 milli m 10 3 kilo k
10 −6 micro µ 10 6 mega M
10 −9 nano n 10 9 giga G
10 −12 pico p 10 12 tera T
10 −15 femto f 10 15 peta P
10 −18 atto a 10 18 exa E
A.4 Basic formulas
Trigonometry
Using a basic right-angled triangle (see figure A.1)
sin θ =
opposite
hypotenuse
sec θ = 1
cos θ
cos θ =
adjacent
hypotenuse
tan θ = opposite
adjacent .
csc θ = 1 cot θ = 1
sin θ
tan θ .
sec = secant csc = cosecant cot = cotangent.