what is the solar system
the sun and all objects orbiting it including planets moons asteroids and comets
what type of object is the sun
a star that produces energy by nuclear fusion
what is the order of planets from the sun
mercury venus earth mars jupiter saturn uranus neptune
what is needed to stay in orbit
a balance between forward velocity and gravitational force
what is the difference between planets and dwarf planets
planets clear their orbit but dwarf planets do not
what is gravity
a force of attraction between masses
why do planets orbit the sun
gravity provides the force needed for circular motion
what happens if velocity increases
orbit becomes larger or object may escape orbit
what happens if gravity increases
orbit becomes smaller and faster
how do stars form
gravity pulls gas and dust together in a nebula forming a protostar
what happens in a main sequence star
hydrogen fusion produces energy and balances gravity
what happens when a star runs out of hydrogen
it expands into a red giant or red supergiant
what happens to small stars after red giant
become white dwarf then black dwarf
what happens to massive stars
explode in a supernova forming a neutron star or black hole
what is red-shift
light from galaxies is shifted towards the red end of the spectrum
what does red-shift show
galaxies are moving away from us
what does a bigger red-shift mean
galaxy is moving faster and is further away
what theory does red-shift support
the big bang theory
what is the big bang theory
the universe began from a hot dense state and has been expanding
what evidence supports the big bang
red-shift and cosmic microwave background radiation
what is cosmic microwave background radiation
leftover radiation from the early universe
how does the universe change over time
it continues to expand and cool
key phrase for star life cycle
balance between gravity and radiation pressure
