life cycle of a star

Question 1

what does the life cycle depend on?

Answer 1

the size of the star

Question 2

life cycle for sun size star

Answer 2

nebula -> protostar -> main sequence -> red giant -> white dwarf -> black dwarf

Question 3

life cycle for bigger than sun size star

Answer 3

nebula -> protostar -> main sequence -> red super giant -> supernova -> neutron star OR black hole

Question 4

describe how the life cycle works for similar size to sun after mains sequence

Answer 4

• eventually hydrogen begins to run out
• star then swells into a red giant
• becomes red as the surface cools
• fusion of helium (and other elements) occur
• heavier elements (up to iron) are created in the core
• then becomes unstable and ejects its outer layer of dust and gas
• leaves behind a hot, dense, solid core (white dwarf)
• as a white dwarf cools down, it emits less and less energy
• when it no longer emits a lot of energy, it is a black dwarf

Question 5

describe how the life cycle works for stars bigger than the sun after main sequence

Answer 5

• eventually hydrogen begins to run out
• star then swells into a red super giant
• becomes red as the surface cools
• fusion of helium (and other elements) occur
• heavier elements (up to iron) are created in the core
• star starts to glow brightly again as it undergoes more fusion and expands and contract several times, forming elements as heavy as iron
• eventually they explode in a supernova, forming elements heavier than iron and ejecting them into the universe to form new planets and stars
• exploding supernova throws outer layers of dust and has into space, leaving a dense core called a neutron star
• if it is large enough it will become a black hole

Question 6

what is a black hole?

Answer 6

a dense point in space

Question 7

how are elements found over the universe?

Answer 7

explosion of a supernova distributes them

Question 8

how do elements occur?

Answer 8

through fusion in stars

Question 9

where are elements heavier than iron produced?

Answer 9

in a supernova

Question 10

where are heavy elements produce, but not heavier than iron?

Answer 10

in the core of a red/red super giant

Question 11

how do fusion processes lead to the formation of elements?

Answer 11

• fusion in stars starts with hydrogen atoms fusing to form helium
• as stars age and run out of hydrogen, they fuse helium into heavier elements like carbon and oxygen.
• in the most massive stars, fusion continues to create elements all the way up to iron.
• when these stars explode in a supernova, they can create even heavier elements, which are then spread throughout space.