Birth, Life And Death Of Stars Flashcards
What are Stars born in?
Stars are born in vast, slowly rotating, clouds of cold gas and dust called nebulae
What are the masses of these nebulae
Between 100 thousand and 2 million times the mass of the sun
What are the diameters of these nebulae
They range from 50 to 300 light year across
What happens to the nebula over time
Over time the clouds contract, become denser and slowly heat up and break up into smaller clumps
What happens to the clumps once they get smaller
They flatten out into disk shapes
What happens to the center of each clump
It will eventually contain a star
What happens to the outer disk of gas and dust
It may eventually form planets around the star
What happens when the contracting clumps continue to heat up
A protostar is formed at the center
What is a protostar?
A protostar is a dense ball of gas that is not yet hot enough at the center to start nuclear reactions
How long does this stage last?
Roughly 50 million years
What happens as the collapse continues?
The mass of the protostar increases
What happens when the mass of the protostar increases
It squeezes it further and increases the temperature
How hot does a protostar need to be in order for nuclear fusion to take place
10 million degrees Celsius
What happens after nuclear fusion is able to take place
The protostar will technically be called a star
How does a young star start converting hydrogen to helium
Via nuclear fusion reaction
What type of energy is produced in vast amounts during nuclear reactions
Heat and light
What does this energy production do?
Prevents the star from contracting any further
What does the star do when it shines?
Blows away the disk of dust and gas surrounding the star
What happens during nuclear fusion
2 or more nuclei combine to form a large, single nucleus
What are star winds called?
Stellar winds
When is a star considered to be born?
Once nuclear fusion reaction begins at its center
What is a main sequence star
A star that is converting hydrogen to helium
How long can a star remain a main sequence star
Millions or billions of years
When are stars most stable?
During their main sequence stage
Which type of star comes in many different sizes and colors?
Main sequence stars
What determines their colours
Their surface temperature
How do you get stars look
They are hotter and blue in colour
What happens to them once they age
They become more yellow and orange and slowly cool down
How do older stars appear
Red and are vastly cooler in temperature
What determines how long a main sequence star lives
How massive it is
What happens when the hydrogen in the center of the star is depleted
He stars core shrinks and heats up
What happens to the outer parts of the star when this happens?
It starts to expand
What happens when a star becomes larger and brighter
It’s surface temperature cools and it glows red
What happens in the next nuclear reaction
Atoms of helium collide and fuse into heavier elements such as carbon and oxygen
After the helium i know the core is depleted, what determines the fate of the star
It’s mass
What happens to medium sized stars
The temperature in the center will never get hot enough for a second nuclear fusion and they don’t evolve any further
What follows the red giant phase?
The star becomes unstable and will eventually die
What are the three stages of the death of stars
- hydrogen starts to run out
- other elements start to burn and give off more heat
- star swells as surface cools —> red
What are the stages of a medium sized star
- star swells and becomes red giant
- outer layer of gas are shed to form a planetary nebula (dust clouds)
- core contacts into white dwarf (dead star)
What are the stages of a large star?
- turns yellow —> red —> super red giant
- explodes as a supernova
- a neutron star and a black hole are left behind
What is a neutron star
Dense dead star
What is a black hole?
Object with a large gravitational pull
