C20 Cosmology

Question 1

Define an astronomical unit

Answer 1

• Average distance from Earth to the Sun.
• 1.5 x 10^11 metres

Question 2

Define light year

Answer 2

• The distance travelled by light in a vacuum, in one year.
• (3 x 10^8) x (365 x 24 x 60 x 60)

Question 3

What are arcminutes and arcseconds?

Answer 3

They are the units used for angles in space.
1 arcminute = 1/60 degrees
1 arcsecond = 1/3600 degrees

Question 4

Define the parsec

Answer 4

• The distance at which a radius of one AU subtends an angle of 1 arcsecond.
• 3.1 x 10^16

Question 5

Relationship between parsecs and arcseconds

Answer 5

Parsecs = 1 / arcseconds