Nebulae and Star Formation
What is a nebula?
A vast cloud of gas and dust in space, often a stellar nursery where stars form.
What is the main sequence?
A stable phase when a star fuses hydrogen into helium in its core.
What color indicates the hottest stars?
Blue or blue-white
What is a black hole?
A region of space where gravity is so strong that nothing, not even light, can escape.
How do we determine a star's composition?
By analyzing its spectrum for absorption/emission lines.
Name three types of nebulae
Emission nebulae (glowing), reflection nebulae (reflecting starlight), and dark nebulae (blocking light).
What happens during a supernova?
A massive star explodes, ejecting its outer layers and leaving behind a neutron star or black hole.
What type of star is our Sun?
A yellow dwarf (spectral type G)
How is a black hole formed?
From the collapse of a massive star's core after a supernova.
What information do dark lines in a spectrum provide?
The elements present, based on which wavelengths are absorbed.
What triggers nuclear fusion in a star?
Gravitational collapse increases core temperatures and pressure until fusion begins.
What is a red giant?
A late-stage star that explodes and cools after exhausting hydrogen in its core.
What spectral type is the coolest?
M-type (red stars)
It cannot escape and falls toward the singularity.
How do we classify stars on the Herzsprung-Russel diagram?
By surface temperature (spectral type) and luminosity (brightness)
What role does gravity play in star formation?
Gravity pulls gas and dust together, increasing density and heat until a star forms.
What are the final stages of a high-mass star?
It undergoes a supernova, then becomes a neutron star or block hole.
What is mnemonic device for spectral types?
O, B, A, F, G, K, M --> "Oh Be A Fine Girl/Guy, Kiss Me"
Stellar-mass are a few to tens of solar masses; supermassive are millions to billions of solar mases, found at galaxy centers.
What can we learn from a star's spectrum?
Temperature, composition, motion (Doppler shift), and sometimes age.
Explain the process of gravitational collapse.
A cloud of gas and dust contracts under gravity, raising temperature and pressure until nuclear fusion stars.
What occurs during the protostar phase?
A collapsing gas cloud heats up into a dense core but hasn't yet started nuclear fusion.
How does temperature relate to a star's color?
Hotter stars look blue/white, cooler stars look yellow/red
Why is the term "suck" misleading when talking about black holes?
They don't pull objects in like vacuums; objects fall in only if they cross their gravitational influence.
What is cosmic equilibrium in relation to stars?
The balance between gravity pulling inward and fusion pressure pushing outward, keeping a star stable.