Flashcards
8. Space physics
Cards in this deck (28)
- 1How do stars form?1. A nebula spirals together into a protostar due to gravity.
2. Gravitational attraction causes its density to increase and its particles to collide more frequently, increasing the temperature.
3. Hydrogen nuclei begin nuclear fusion and form helium nuclei, and the energy emitted keeps the core hot. - 2What is a nebula?A nebula is a cloud of dust and gas that is the initial stage of a star's formation.
- 3What is a protostar?A protostar is a a contracting mass of dust and gas that is the stage of a star's formation before nuclear fusion has begun.
- 4Why do newly formed stars enter a long stable period?The energy released by nuclear fusion provides an outward pressure that balances the force of gravity so it is in equilibrium.
- 5What is a main sequence star?A main sequence star is one that is in its long stable period.
- 6Why do stars leave their long stable periods?Eventually the hydrogen begins to run out so fusion of helium and other elements occur, creating heavier elements in the core.
- 7What elements can be produced by stars?Every naturally occurring element in the universe are produced by stars.
- 8What happens to a star around the size of the Sun when hydrogen begins to run out?1. It expands into a red giant.
2. The star becomes unstable and ejects its outer layer of dust into a planetary nebula and a white dwarf is left.
3. It becomes a black dwarf and eventually disappears from sight. - 9What is the difference between a white dwarf and a black dwarf?A white dwarf is the hot, dense core left when a smaller star becomes unstable and a black dwarf is what it becomes when it no longer emits a significant amount of energy.
- 10What happens to a star much larger than the Sun when hydrogen begins to run out?1. It expands into a red super giant that expands and contracts several times forming elements as heavy as iron.
2. The star runs out of elements to fuse and becomes unstable before exploding in a supernova, forming elements heavier than iron and ejecting them.
3. A neutron star or a black hole is left. - 11Why do stars become red when they become red giants/super giants?They become red because the surface cools.
- 12What is a supernova?A supernova is a star that is undergoing an explosion that ejects most of its mass.
- 13What is a neutron star?A neutron star is the very dense core left when a larger star explodes if it is not large enough to produce a black hole.
- 14What is a black hole?A black hole is a region of space left when a very large star explodes that has a gravitational field so intense that no matter or radiation can escape.
- 15What are planets?Planets are objects that orbit a star and are large enough to have pulled any nearby objects from their natural satellites.
- 16What are dwarf planets?Dwarf planets are objects that orbit a star but do not fulfil the requirements to be a planet.
- 17What are satellites and some examples?Satellites are objects that orbit a larger object such as moons and artificial satellites.
- 18How does the circular shape of an orbit affect its acceleration, velocity and speed and why?In a circular orbit, an object is constantly accelerating because it is constantly changing direction, which means it is also constantly changing velocity although the speed stays the same.
- 19What is the force acting on an orbiting object, where is it directed and what action is it needed for?The force of gravity between a planet and a Sun or a planet and its satellites is directed towards the centre of the circle and is needed for an object to accelerate.
- 20What is instantaneous velocity?Instantaneous velocity is the velocity of an object in motion at a specific point in time.
- 21Why does an object go into orbit?The gravitational force of the larger object attracts the smaller object, causing it to accelerate towards it, but the smaller object's instantaneous velocity is perpendicular to this so the object travels in a circular motion.
- 22How does an orbiting object's speed depend on the radius of an orbit and why?The smaller the radius, the faster the smaller object needs to travel to remain in orbit. This because the the closer the objects are, the stronger the gravitational force of the larger object is.
- 23What is red-shift?Red shift is the effect seen when viewing light from distant galaxies that causes the wavelengths to be longer (towards the red end of the EM spectrum).
- 24Why does red-shift occur?Red-shift occurs because the source of the light is moving away from the observer, as if the wave is stretching out.
- 25Why have we concluded that the universe is expanding and why do galaxies not expand with it?More distant galaxies have a greater red-shift than nearer ones, meaning they are receding at a faster rate, which suggests all galaxies are moving away from each other and the whole universe is expanding. However galaxies do not stretch as they are held together by gravity.
- 26What is the Big Bang Theory?The Big Bang Theory states that for the universe to be expanding, it must have once been in an unimaginably dense space and exploded.
- 27Why have we concluded that the expansion of the universe is accelerating?Observations of supernovae appear to show the speed at which galaxies are receding is increasing in speed, though we don't yet know how or why.
- 28What is the difference between dark matter and dark energy?Dark matter is the unknown substance which holds galaxies together but does not emit electromagnetic radiation, whereas dark energy is thought to be responsible for the accelerating expansion of the universe.
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- GCSE Physics Flashcards on 8. Space physics, created by JR HN on 09/10/2018.
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