Ch. 18 Flashcards
30 light years from Sun
Most common are M stars // dwarf stars everywhere, just dim and hard to see
Binary Stars
Two stars that orbit each other, bound together by gravity // Make up half of stars in sky
Visual Binary
Binary star system in which both stars can be seen without telescope
Center of Mass
Higher mass star in binary system closer to the center
Spectroscopic Binary
Has same radial velocity when both stars moving across our line of sight, appearing as a single star in spectroscopy
Optical Double
A pair of stars that appear close together in the sky, but do not orbit each other
Brown Dwarfs
Can be seen in infrared light
Mass / Luminosity
Higher mass = higher luminosity (L ~ M^3.9)
Eclipsing Binary Star Systems
Light from both stars fluctuate due to eclipses over the time span of an orbit
Points of Contact
First: Smaller star starts to pass behind the larger star
Second: Total eclipse
Third: Smaller star begins to emerge
Last: Eclipse over
Diameters of Eclipsing Binary Stars
Smaller Star: Speed * interval between 1&2 contact
Larger Star: Speed * Interval between 1-3 contacts
Measuring Surface Temp
- Determine color roughly
2. Measure the spectrum & get spectral type
Measuring Chemical Composition
Determine which lines are present in the spectrum
Measuring Luminosity
Measure apparent brightness and compensate for distance
Measuring Radial Velocity
Measure Doppler shift in the spectrum
