Figures and formulae

Question 1

Diameter of the Earth

Answer 1

13000 km

Question 2

Diameter of the Moon

Answer 2

3500 km

Question 3

Diameter of the Sun

Answer 3

1.4 million km

Question 4

Distance from the Moon to the Earth

Answer 4

380 000 km

Question 5

Distance from the Sun to the Earth

Answer 5

150 million km

Question 6

One astronomical unit (AU)

Answer 6

mean distance between the Earth and Sun

150 million km

Question 7

Rotation period of the Earth

Answer 7

23 hours 56 minutes

Question 8

Time for the Earth to rotate through 1 degree

Answer 8

4 minutes

Question 9

The Moon’s rotational period and orbital period

Answer 9

27.3 days

Question 10

The period of the lunar phase cycle

Answer 10

29.5 days

Question 11

Temperature of the Sun’s photosphere

Answer 11

5800 K

Question 12

Approximate temperature of the corona

Answer 12

2 million K

Question 13

Kepler’s third law

Answer 13

T^2 = R^3

where T is in years and R is in AU

Question 14

Circumpolar stars

Answer 14

declination > 90 – latitude

Question 15

Magnitude calculations

Answer 15

M = m + 5 — 5 log d

where m is apparent magnitude, M is absolute magnitude and d is distance (parsecs).

Question 16

Radial velocity of a galaxy

Answer 16

(λ- λ0) / λ0 = v / c

where v is the radial velocity, c is the speed of light, λ is wavelength and λ0 is the rest wavelength.

Question 17

Hubble’s Law

Answer 17

v = Hd

where v is velocity, d is distance and H is the Hubble constant.