Astrophysics &Cosmology

Question 1

Astronomical Units (AU)

Answer 1

Earth to the Sun 1.496 x 1011 metres ~1.5 x 1011 metres

Question 2

Parsecs (pc)

Answer 2

3.086 x 1016 metres ~3.1 x 1016 metres (1 AU)/tan⁡〖 (( 1)⁄(3600 ))〗

Question 3

Light-Years (ly)

Answer 3

9.461 x 1015 metres ~9.5 x 1015 metres

Question 4

Hubble’s Law

Answer 4

The speed of recession of a galaxy is directly proportional to its distance from Earth.

Question 5

Critical Density

Answer 5

A density level above which the universe will head back to a “Big Crunch”.

The fate is summarised as: ρo = constant x Ho2.

Density > ρo – universe is closed, the crunch is coming.

Density < ρo – universe is open, expands forever.

Density = ρo – universe is flat, expands forever but the rate reduces to zero after infinite time.