Star Formation
What two forces fight each other during star formation?
Gravity vs. pressure
What will the Sun eventually become?
A white dwarf
What does redshift tell us about distant galaxies?
They are moving away
What two variables are plotted on the H-R diagram?
Temperature and luminosity
What causes dark absorption lines?
Elements absorbing specific wavelengths of light
What event marks the transition from protostar to main sequence?
The start of hydrogen fusion
What causes a star to expand into a red giant?
The core runs out of hydrogen and contracts
Why is the CMB so cold today?
The universe expanded and cooled over billions of years
Where are the hottest stars located?
Upper left
A star with strong iron lines has high or low metallicity?
High
What causes a nebula to begin collapsing?
Uneven density leading to gravitational collapse
Which stars explode as supernovae?
High-mass stars
What do small temperature variations in the CMB represent?
Early clumps where galaxies later formed
What determines where a star falls on the main sequence?
Its mass
If a star’s spectrum is shifted to shorter wavelengths, what is happening?
It’s moving toward us (blueshift)
What process grows a forming protostar as dust and gas stick together?
Accretion
What determines whether a supernova leaves a neutron star or black hole?
Mass of the collapsing core
Why do hydrogen and helium abundances support the Big Bang?
They match predicted early universe ratios
Stars in the lower right of the diagram are what type?
Cool and dim
Why do different elements produce different line patterns?
Each element absorbs light at unique energy levels
Why do stars form only in certain parts of molecular clouds?
Those regions are denser and colder, allowing collapse to begin
Why does fusion stop after iron forms in a massive star?
Fusing iron requires more energy than it releases
What type of radiation is the CMB?
Microwave radiation
Why are giant stars so luminous even if they’re cooler than the Sun?
Their large radius increases energy output
What can spectra reveal about a star besides composition?
Motion (redshift/blueshift) and relative temperature