Assignments for Tues. 27Feb

• Review secs. 6-10 of DocOnotes-stars1– practice Quick Questions at end of sections

• Complete HW2.pdf, due classtime Tues. 27Feb

1

Surface gravity

2

Orbital speed

3

Escape speed

4

Virial theorum for bound orbits

5

Clicker question

A. 4.4B. 5.4C. 3.9D. 3.4E. Not enough information to answer.

In cgs units, the log of sun’s gravity is log gsun=4.4. What is log g for a star with with mass M=10 Msunand radius R=10 Rsun?

Clicker question

A. 62 km/sB. 620 km/sC. 6200 km/sD. 200 km/sE. 2000 km/s

The sun has an escape speed Ve,s=620 km/s. What is the escape speed from a star with mass M=10 Msun and radius R=10 Rsun?

Clicker question

A. 3 km/sB. 30 km/sC. 300 km/sD. 90 km/sE. 900 km/s

The earth at 1 au from the sun has an orbital speed Ve=30 km/s. What is the orbital speed of a planet orbiting a star of mass M=10 Msunat a distance of d=0.1 au?

Inferring stellar motion

• Across the sky– “Proper motion”

• Toward/away from us– “Radial velocity”– Doppler shift

10

Proper Motion & Tranverse Speed

11

12

13

14

15

16

17

Doppler shift and Radial velocity

19

20

observer

21

22

23