Download Astronomy I Ex.2

Astronomy I Ex.2
1. Convert the following distances into distances in cm:
a) 1 Lyr.
b) 50 Mpc.
c) 100,000 AU.
2. H0 ' 70 secKm
M pc
What is the (approximate) age of the universe in Gyr?
3. Convert the following distances in cm to distances in AU:
a) Approximate distance from the earth to the sun: 1.44 × 1013 cm
b) Approximate distance from the earth to the next nearest star - Alpha
Centauri: 3.97 × 1018 cm
c) Approximate distance from the earth to a galaxy in the Virgo constellation: 4.91 × 1025 cm
4. There are ∼ 1012 stars in a galaxy, and the radius of the galaxy is 20 Kpc.
What is the velocity of a star at the edge of the galaxy. (relative to the
galaxy’s center)?
* Assume the average mass of a star is one solar mass.
5. If a star has a parallax of 0.1 arcsec, what is the distance in pc from the
star to us?
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