Astrophysics and cosmology Flashcards
(14 cards)
Define planets
- spherical objects with mass
- no fusion occurs
- object has cleared its orbit of other objects
dwarf planets
planets where the orbit has not been cleared of other objects
planetary satellites
bodies that orbit a planet
asteroids
- too small and uneven to be panets
- near circular orbit around sun
comets
rock that orbit the sun in eccentric, elliptical orbits
solar systems
system containing state and orbiting objects (like planets)
galaxies
Collection of stars, dust and gas
nebula
clouds of dust and gas
how are protostars formed
-In nebulae, regions are more dense that others
- gravity draws matter towards them and combined with angular momentum, causes them to spin inwards to form a denser centre
- gpe is converted to thermal energy, which heats up centre resulting in hot dense sphere (protostar)
how are main sequence forced
- temperature high enough for hydrogen gas nuclei in protostar to overcome electrostatic forces of repulsion and undergo nuclear fusion converting hydrogen into helium
- protostar becomes main sequence where the outward pressure due to fusion and inward force of gravity are in equilibrium
how do low mass main sequence stars become red giants?
- hydrogen runs low and gravitational forces inwards overcome gas pressures.
- core collapses inwards and out layers expand and cool
- core becomes hotter and starts to fuse helium into elements (up to carbon)
what happens when you go from a red giant to a white dwarf?
- star runs out of fuel
- expels outer layers creating a planetary nebula
- electron degeneracy pressure prevents core from collapsing
- as long as core is below 1.44M, then white dwarf is stable (chandrasekhar limit)
how does a high mass main sequence star turn into red a SUPERgiant?
- hydrogen supplies deplete and core contracts
- greater mass so hotter than red giant
- fusion heavier than carbon (up to iron)
- outer layers expand and cool forming red supergiant
