Fichas
Topic 8 - Space physics
Fichas del conjunto (11)
- 1What happens for the first three stages of a star's life cycle?1. stars initially form a cloud of dust and gas called a nebula. The force of gravity pulls the dust and gas together to form a protostar.
2. as the star gets denser, the temperature rises and more particles collide with each other. When the temp gets high enough, hydrogen nuclei undergo nuclear fission to form helium nuclei. This gives out huge amounts of energy, which keeps the core of the star hot, a star is born.
3. the star enters a long stable period where the outward radiation pressure balances the force of gravity inwards. In this stable period, it's called the main sequence star and it typically lasts several billion years, the sun is in this stable period. - 2What happens for the last three stages after the main sequence star turns into a red giant?1. eventually the hydrogen begins to run out, the star swells into a red giant (if it's a small star). It becomes red because the surface cools. Fusion of helium (and other elements) occur. Heavier elements (up to iron) are created in the core of the star.
2. a small-to-medium sized star like the sun then becomes unstable and ejects its outer layer of dust and gas. This leaves behind a hot, dense, solid core - a white dwarf.
3. as a white dwarf cools down, it emits less and less energy. When it no longer emits a significant amount it is called a black dwarf. - 3What happens for the last three stages after the main sequence star turns into a red supergiant?1. eventually the hydrogen begins to run out. the star then swells into a red supergiant ( if it's a larger star). It becomes red because the surface cools. Fusion of helium ( and other elements) occurs. Heavier elements (up to iron) are created in the core of the star.
2. big stars, start to glow brightly again as they undergo more fusion and expand and contract several times, forming elements as heavy as iron and ejecting them into a universe to form new planets and stars. Star and their life cycles produce and distribute all naturally occurring elements.
3. the exploding supernova throws the outer layers of dust and gas into space, leaving a very dense core called a neutron star. If the star is massive enough, it will become a black hole - super-dense point in space that not even light can escape from. - 4Name the planet from closest to the sun?mercury
venus
earth
mars
jupiter
saturn
uranus
neptune
dwarf planet (pluto) - 5What are planets, dwarf planets, moons and artificial satellites?Planets - large objects that orbit a star. They have to be large enough to have "cleared their neighbourhoods" meaning their gravity is strong enough to have pulled in any nearby objects apart from their satellites.
Dwarf planets - planet-like objects that orbit stars but don't meet all the rules for being a planet.
Moons - these orbit planets and are a type of natural satellite.
Artificial satellites - satellites humans have built, generally, orbit the earth.
Our solar system is a tiny part of the Milky Way galaxy - a massive collection of billions of stars all held together by gravity. - 6How is an orbit created?1. Planets move around the sun in almost circular orbits.
2. if an object is travelling in a circle it is constantly, which means an object is constantly accelerating. This also means it is constantly changing velocity (not speed).
3. for an object to accelerate there must be a force acting on it. This force is directed towards the centre of the circle.
4. this force would cause the object to just fall towards whatever it was orbiting, but as the object is already moving, it just causes it to change its direction.
5. the object keeps accelerating towards what its orbiting but the instantaneous velocity (which is at a right angle to the acceleration) keeps travelling in a circle.
6. the force that makes this happen is provided by the gravitational force between the planet and the sun (or between planets and satellites). - 7What does the size of an orbit depend on?1. the closer you get to a star or planet, the stronger the gravitational force is.
2. the stronger the force the faster the orbiting object needs to reavel to remain in orbit (to not crash into the object that it's orbiting). For an object in a stable orbit, if the speed of the object changes, the size (radius) of its orbit must do so too. Faster moving objects will move in a stable orbit with a smaller radius than slower moving ones. - 8What is red-shift?When we look at light from most distant galaxies, we find that the wavelength has increased. The wavelengths are all longer than they should be - they're shifted towards the red end of the spectrum.
- 9How does red-shift suggest the universe is getting bigger?Red-shift suggests the source of the light is moving away from us. Measurements of the red-shift indicate that these distant galaxies are moving away from us (receding) very quickly - and it's the same result whichever direction you look in. More distant galaxies have greater red-shifts than nearer ones. This means that more distant galaxies are moving away faster than nearer ones. This means that more distant galaxies are moving away faster than nearer ones - and so all galaxies are moving away from every other galaxy, not just ours. Therefore space itself is expanding.
- 10Why does this suggest the universe started with a big bang?So all the galaxies are moving away from eachother at a great speed - suggesting something must have go t them going.
1. initially all the matter in the universe occupied a very small space. This tiny space was very dense and so was very hot.
2. then it exploded - space started expading and the expansion is still going on. - 11Explain how these thoeries may change?Big bang is the best thoery we have so far but scientists may discover new evidence leading to a new thoery etc.