Lecture 3: Stars And Galaxies Flashcards
What is a star?
Gas (hydrogen and helium)
What are the properties of stars?
Magnitude, luminosity, luminosity and spectra, color and temperature
What is magnitude?
The measure of a stars brightness, based on distance.
How is magnitude measured?
Measured in two ways: apparent and absolute magnitude (true brightness of a star)
What numbers are given to stars that are dimmer than the sun?
Higher than five
What numbers are given to stars that are brighter than the sun?
Lower than five
What is luminosity?
Total amount of energy emitted by a star, related to absolute magnitude.
How does luminosity vary with the size of the star?
Same size star; hotter is more luminous
How does luminosity vary with the temperature of the sun?
Same temp star; larger is more luminous
Blue Stars
Hot
Yellow stars
Mid temp - sun
Red stars
Cold
How are types of stars defined?
Their properties
What are the four types of stars?
Main sequence (sun)
Giants
Super giants
Remnant stars (white dwarfs and black holes)
What is every star stage controlled by?
Gravity
What are the three general stages of a star?
Star birth
Stellar stage
Death
Celestial objects in a star birth?
Nebula and protostar
Celestial objects in stellar stage?
Main sequence, red giant, planetary nebula
Celestial objects in a star death?
White dwarf
What is a nebula?
A cloud of dust and gas
What is the composition of a nebula?
Hydrogen 90%
Helium 9%
What characterizes the suns evolution in the nebula stage?
No hydrogen burning (fusion)
Why is the evolution of low mass stars not understood?
None have died yet
What type of remnant stars with large mass stars become?
Blue stars
