astro physics and cosmology Flashcards
planet
objects with mass sufficient for their own gravity to force them to take a spherical shape, no nuclear fusion occurs, cleared orbit of other objects
dwarf planets
planet where the orbit has not been cleared of other objects
planetary satellite
Bodie that orbits a planet
asteroid
objects which are too small and uneven to be planets, near circular orbit around the sun
comets
small, irregularly sized balls of rock, dust and ice. they orbit the sun in an elliptical orbit
solar system
systems containing stars and orbiting objects like planets
galaxy
collection of stars, dust and gas
nebulae
gigantic clouds of dust and gas
protostar formation
- nebulae with dense regions of dust and gas
- gas pulls dust and gas together causing it to collapse
- as cloud collapses, its starts to spin and forms a rotating disk (angular momentum causes the spin)
- centre of disk, a dense core forms
- gpe is converted to thermal which heats up centre
- sphere of very hot, dense, dust and gas which os called a protostar
how are main sequence stars formed from protostars
- when protostar formed from a cloud of gas and dust, gravity pulls the material inward
- as material gets closer togther it becomes denser and hotter
- the increase in denisty and temperature leads to an increase in pressure
- pressure comes from gas particles colliding and pushing outwards
- the temp and pressure must then be high enough for hydrogen to overcome elcatrostatic forces of repulsion and undergo nuclear fusion where hydrogen is fused to helium
- fusion will occur when the pressure outward pressure balances the inward force of gravity
how does a low mass main sequence star become a red giant
- core mass of 0.5 solar masses
- smaller cooler core they remain in main sequence longer
- hydrogen supplies low g forces inwards overcome radiation and gas pressures
- core collapses and outer layers expand and cool
- core of red giant becomes hotter as gpe becomes thermal energy and it fuses helium into heavier elements up to carbon as hydrogen continues to be fused in the layers around the core
red giant to white dwarf
- star runs out of fuel it expels its outer layers resting planetary nebulae
- core contracts further becoming dense white dwarf
- no fusion occurs
- photon which were produced earlier leak out dissipating heat
- star core collapses electron degeneracy pressure prevents the. core form collapsing, as long as core mass is below 1.44 then the white dwarf is stable this is the Chandrasekhar limit
high mass main sequence into red supergiant
- mass exceeds 10 solar masses
- hydrogen supplies deplete
- core contracts
- as mass is greater when gpe is converted to thermal energy the core gets hotter than red giant allowing helium fusion into heavier elements than carbon up to iron
- outer layers expand and cool forming red supergiant
death of high mass star
- fuel in red supergiant used up fusion stops
- gravity becomes greater than outward pressure due to fusion
- core collapses in on itself and becomes rigid
- outer layers fall inwards and rebound off the core launching them into space as a shockwave
- remaining core of a supernova is either a neutron star or black hole depending on mass
red supergiant into neutron star or black hole
- core greater than 1.44 gravity forces protons and electrons to combine and form neutrons this produces small dense neutron star
- core greater than 3 the gravitational forces are so strong that the escape velocity of the core becomes greater than the speed of light this is a black hole
hertzprung - russel diagram
- top supergiants
- middle right giants
- negative linear line main sequence
- bottom left white dwarf
