space Flashcards
(12 cards)
describe the process of nuclear fusion
• two (small) nuclei
• join together to produce a larger nucleus
• releasing energy
what is the name of the force that keeps all the planets in the Solar System in orbit around the Sun
gravitational pull
(NOT GRAVITY)
what two factors determine the size of gravity on the surface of a planet
mass and radius (of planet)
describe how the speed of a comet changes as it approaches the Sun
speed increases as distance from sun decreases
describe the creation of a nebula
• a cloud of dust and gas in space (largely hydrogen)
• collapses under gravitational forces
• GPE transfers to KE and thermal energy, increasing temperature
• moves to the main sequence when temperature and pressure are high enough for hydrogen fusion to begin
describe the creation of a main sequence
• hydrogen fuses to helium in the core
• stable star as weight is balanced by thermal expansion (pressure due to fusion)
• high mass stars stay on the main sequence for less time than low mass main sequence
• when the star (begins) to run out of hydrogen, the core collapses
• moves to the red giant / red supergiant when temperature and pressure are high enough for helium fusion to begin
describe the creation of a red giant / red supergiant
• helium fuses to heavier elements in the core
• stable star as weight is balanced by thermal expansion (pressure due to fusion)
• lower surface temperature than the main sequence phase
• when the star (begins) to run out of helium, the core collapses
describe the creation of a supernova
• when a red supergiant (begins) to run out of helium, the core collapses
• temperature and pressure of the core increase until fusion of heavy elements begins
• the sudden release of energy leads to an explosion
• the explosion leaves behind a nebula, and a neutron star, or a black hole for the highest mass stars
the life cycle of a star begins in a nebula, describe how a main sequence star is formed from a nebula
• nebula is a (cold) cloud of dust / gas
• gravity causes cloud to collapse
• temperature of cloud increases
• creating a protostar
describe how a main sequence star becomes a white dwarf
• core collapses
• core temperature of star increases
• becomes a red (super) giant
• surface temperature of star decreases
• helium fusion begins
• white dwarf formed when helium fusion stops
main sequence stars can vary in brightness, colour and mass - describe the evolution of both low mass stars and high mass stars after they join the main sequence
low mass stars:
• the star becomes a Red Supergiant
• it then turns into a White Dwarf and a Nebula
high mass stars:
• the star becomes a Red Supergiant
• it then turns into Supernova
• then it forms a Neutron Star and a Nebula or a Black Hole and a Nebula
describe how a star is formed in a nebula
