| Today: Chapter 8, Properties of Stars |
| L = 4 p R2 sT4 | ||
| The main sequence consists very roughly of similar size stars | ||
| The giants, supergiants, and white dwarfs are much larger or smaller | ||
Lines of constant R in the H-R diagram
Different “types” of H-R diagrams
Spectra of Different Luminosity Classes
What fundamental property
of a star
varies along the main sequence?
What fundamental property
of a star
varies along the main sequence?
| Two types of binary stars | |||
| Visual binaries: See separate stars | |||
| a large, P long | |||
| Can’t directly measure component of a along line of sight | |||
| Spectroscopic binaries: See Doppler shifts in spectra | |||
| a small, P short | |||
| Can’t directly measure component of a in plane of sky | |||
| If star is visual and spectroscopic binary get get full set of information and then get M | |||
| Main Sequence position: | ||
| M: 0.5 MSun | ||
| G: 1 MSun | ||
| B: 40 Msun | ||
| Luminosity Class | ||
| Must be controlled by something else | ||
The Mass-Luminosity Relationship
| L = M3.5 |
| System seen “edge-on” | |||
| Stars pass in front of each other | |||
| Brightness drops when either is hidden | |||
| Used to measure: | |||
| size of stars (relative to orbit) | |||
| relative “surface brightness” | |||
| area hidden is same for both eclipses | |||
| drop bigger when hotter star hidden | |||
| tells us system is edge on | |||
| useful for spectroscopic binaries | |||