Space

You may find some abbreviations used on other web sites you visit. These are some of the most common.

. Degree

• arc minute = 1/60th of a degree
• arc second = 1/3600th of a degree
• 15° =  1 hour
• 1 degree =    4 minutes

Apparent = 'Real Sun time'
Mean = ' Human time'

The mean average distance from Earth to the Sun is 149,600,000 km, normally rounded to 150,000,000 km. This is called 1 Astronomical Unit, or AU, a standard number in astronomy.

The formula for working out if a star is circumpolar or not is
D >= 90° - L

D = Declination
> = = Greater than or equal to
L = Latitude

Right Ascension: How far an object is along the celestial equator from the first point of Aries (where the Sun crosses the Celestial Equator at the Vernal Equinox)
Measured in hours (h), minutes (m) and seconds (s) and is abbreviated as RA or α.

Declination: How far north and south an object is from the Celestial Equator measured in degrees (°), arc minutes (‘) and arc seconds (“) and is abbreviated as dec (δ).
Arcturus: Dec: +19° 10′56″

Altitude
How high an object is above the horizon from 0° at the horizon to 90° at the zenith

Azimuth
How far an object is eastwards in° from north

• 1 AU = 150,000,000 (1.5 x 108)
• 1 Light Year = 9,460,000,000,000 km (9.46 x 1012)
• 1 Parsec = 3.26 light years

N = R* x f_p x n_e x f_l x f_i x f_c x L

• N is the number of civilizations in our galaxy with which communication might be possible;
• R* is the average rate of star formation in our galaxy
• fp is the fraction of those stars that have planets
• ne is the average number of planets that can potentially support life per star that has planets
• fℓ is the fraction of the above that actually go on to develop life at some point
• fi is the fraction of the above that actually go on to develop intelligent life
• fc is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
• L is the length of time such civilizations release detectable signals into space.

v = Hd

v = velocity
H = Hubble Constant
d = distance

Multiply by the square

Example: Planet A is twice as near to the Sun as Planet B. It receives four times as much light as Planet B.
2 x 2 = 4.

1. Planets move in elliptical orbits around the Sun.

2. The Sun-planet line sweeps out equal areas in equal times. Planets move faster when they are nearer the Sun (perihelion) and slower when they are further away (aphelion).

3. T² = r³ (Approximate value)

T = Period/ Time it takes to orbit the Sun
r = mean radius from Sun in AU

Latitude: North Pole: 90°N | Equator: 0° Latitude | South Pole: 90°S
Longitude: The measurement east or west of the prime meridian:
4 minutes = 1 degree of longitude, 1 hour = 15° of longitude

• Greenwich Mean Time Global Time
• Go somewhere Latitude / Longitude Finder

Light year (l.y.) = the distance travelled by light in a vacuum in 1 year (63 240 AU)

M = Absolute Magnitude
m = Apparent Magnitude
d = distance in parsecs

To work out Absolute Magnitude;
M = m + 5 - 5 log d

To work out Apparent Magnitude;
m = M-5+5 log d

Watt (W) = Joule per second

D = Distance
π = Parallax Angle

π = D/1

Parsec (pc) = the distance at which a star would have parallax of 1 second of arc (3.26 light years.)

Large or Small number can be abbreviated.

10^-2 = 1/(10 x 10) = 0.01
10-1 = 1/10  = 0.1
10⁰ = = 1      
10¹ = 10 = 10    
10² = 10 x 10 = 100
10³ = 10 x 10 x 10 = 1000
10⁶ = 10 x 10 x 10 x 10 x 10 x 10 = 1,000,000
M = Mega = Million
K = Kilo = Thousand

Sidereal: An object measured against the background stars
Solar: An object measured against the Sun

Speed of light =  300,000 km/s Use 24hr clock e.g. 4pm = 16.00 hrs

• Celsius (°C) - 0°C = 273 K
• Kelvin (K) - 0 K = - 273°C
• Fahrenheit = (9/5)°C + 32

λ = wavelength
v = recession velocity
c = speed of light