Ch - 25 (Stars and the Universe) Flashcards
What role does the sun play in the solar system?
- medium sized star
- hydrogen and helium
- radiates infrared, UV, and visible light
How are stars classified?
- Colors
- depends on how hot they are
What is a star’s colour related to?
Surface temperature.
What’s the range of star colors from hottest to coldest?
- Blue start is hottest (30 000 K)
- Red star is coolest (3000 K)
What happens at the center of a stable star?
Hydrogen nuclei undergo nuclear fusion to form helium
What happens during nuclear fusion?
- huge amount of energy is released.
- provides pressure for star that prevents it from collapsing under it’s gravity.
What are galaxies made up of?
Made up of billions of stars.
What is the universe made up of?
made up of many different galaxies
What is astronomical distance?
-distance between stars and galaxies
- very large
- light years
Define one light year.
The distance travelled by light through (the vacuum of) space in one year.
What is the speed of light known as?
Universal speed limit
- tracked slowly as compared to astronomical distances .
What is the diameter of the milky way?
100 000 light years
What is one light year equal to?
9.5 x 10 ^12 Km
9.5 x 10^15 m
What are the main stages of star formation?
- Nebula
- Protostar
- Main sequence star
- low mass star
- High mass star
What happens in the stage of nebula in star formation?
Form a giant interstellar cloud of hydrogen gas and dust called a nebula.
What happens in the stage of protostar in star formation?
- Force of gravity pulls nebula closer together forming a hot ball of gas known as protostar
- particles pulled closer, density of protostar increases
-frequent collisions causing temp to increase
What happens in the stage of main sequence star in star formation?
- when protostar is hot, nuclear fusion happens.
- hydrogen nuclei fuse together to form helium nuclei
- fusion reaction releases heat (and light)
- star is in equilibrium, and is stable
- inward force due to gravity is equal to outward pressure force from fusion reaction
What are the stages in low mass life cycle of a star?
- Red giant
- Planetary nebula
- White dwarf
- Black dwarf
What happens in the stage of red giant in star formation?
- fusion reaction in star runs out
- core starts to die down
- core shrinks (inward force of gravity will become greater than the outward force) and heats up
- helium undergo fusion to form beryllium
- cause outer part of star to expand
- 8 times the mass of the sun
- outer surface cools and turns red
What happens in the stage of main planetary nebula in star formation?
- star becomes unstable
- eject outer layer of dust and gas which is called planetary nebula
What happens in the stage of white dwarf in star formation?
- core collapses completely due to pull of gravity
- White dwarf cools
- amount of energy it emits decreases
What happens in the stage of Black dwarf in star formation?
- lost significant amount of energy
- cools until it eventually disappears