P16: Space Physics (Y11 - Spring 2) Flashcards
🟢 Describe the similarities and differences between planets and comets
Planets are objects that obrit around a star, e.g the sun, and are far larger than comets. Comets are irregular shapes that are frozen rocks that move around the sun in obrbits that are elliptical in shape. These elliptical orbits take them far away from the Sun.
🟢 Explain why a comet cannot be seen when it is far away from the Sun
Their elliptical orbits take them far away from the Sun. You only see them when they return near the Sun because then they heat up so much that they emit light.
🟢 Write one difference and one similarity between a comet and an asteroid
Similarity:
- Both asteroids and comets orbit around the sun in some way
Difference:
- Asteroids do not have the ice present in comets
- (Asteriods orbit in a near circular shape, and comets in an elliptical shape)
🟢 Description of the Sun
A star that formed billions of years ago from clouds of dust and gas pulled together by gravitational attraction.
🟢 Description of Planets
A planet is an object in orbit around a star
🟢 Description of Moons
A body in orbit around a planet.
🟢 Description of Comets
Frozen rocks that move around the sun in orbits that are elliptical in shape. These elliptical orbits take them far away from the Sun. You only see them when they return near the Sun because then they heat up so much that they emit light.
🟢 Description of Meteors
Meteors or shooting star are small bits of rocks that burn up when they enter the Earth’s atmosphere.
🟢 Description of Minor (dwarf) Planets
A dwarf planet,like Pluto, has one important difference from a planet. Dwarf planets have not cleared their orbit of other objects. In Pluto’s case there are many other bodies of comparable size close to its orbit.
🟢 Description of Asteroids
Asteroids are objects to small and uneven to be planets, usually in near-circular orbits around the Sun and without the ice present in comets.
🟢 What is the Main Sequences in Stars, How does it happen, and Why does it happen
Stars such as the Sun radiate energy because of hydrogen fusion in the core. They are called main sequence stars because this is the main stage in the life of a star. Such stars can maintain their energy output for millions of years until there are no more hydrogen nuclei left to fuse together.
● Energy released in the core keeps the core hot, so the process of fusion continues. Radiation such as gamma radiation flows out steadily from the core in all directions.
● The star is stable because the forces within it are balanced:
➢ The force of gravity acts inwards trying to make the star contract.
➢ The outward force of radiation from the nuclear fusion in its coretrying to make the star expand.
These forces stay in equilibrium until most of the hydrogen nuclei in the core have been fused together to form helium nuclei.
🟢 How is a Star Born?
Huge clouds of dust and hydrogen gas in space are pulled together by their gravitational attraction. Those clouds join, becoming more and more concentrated, forming a protostar. As the protostar becomes dense, it gets hotter and this energy causes lighter nuclei to join together, energy is released from this fusion reaction, making the protostar even hotter. The outwards force from the pressure of expanding hot gas is balanced by the force of the star’s gravity acting inwards on the star. As it gets hotter and brighter, the star starts to shine, therefore giving birth to a star.
(Then the stars gravity pulls smaller amounts of dust and gas together forming planets in orbit of the star.)
🟢 State why a star is stable during the ‘main sequence’ period of its life cycle.
Because the outwards pressure caused by radiation from the nuclear fusion in its core is equal to inwards force of gravitational attraction acting upon the star.
🟢 How is a Star Created (kerboodle)
- The particles in the clouds are pulled together by their own gravitational attraction so the particles speed up. The clouds merge together and become more and more concentrated to form a protostar, which is a star-to-be
- As a protostar becomes denserm its particles soeed up more and more and collide more, so it’s temperature increases and it gets hitter. The process transfers energy from the prostar’s gravitational potential energy store to its thermal energy store. If the protostar becomes hot enough, the nuclei of hydrogen atoms fuse together, forming helium nuclei. Energy us released in this fusion, so the protostar gets hotter and brighter and starts to shine.
- Objects can form that are too small to become stars. These kinds of objects can be attracted by a protostar to become planets orbiting the star.
🟢 What are the Stages of Stars that are the same size as our Sun
- Protostar
- Main Sequence Star
- Red Giant
- White Dwarf
- Black Dwarf
🟢 What are the Stages of Stars that are much bigger than the Sun
- Protostar
- Main Sequence Star
- Super Red Giant
- Supernova
- Neutron Star | Black Hole
🟢 What happens to Stars with low-masses as they get older
Stars with low masses remain in their main sequence for much longer, as their core is cooler than that of more massive stars.
However, eventually, after billions of years, they run low of hydrogen fuel in their core. At this stage, they begin to move off the main sequence into the next phase of their lives.
🟢 Full Life Cycle of Stars with Low Mass
- The cloud of gas and dust heats as it contracts. When it is hot and dense but nuclear fusion has not yet started it is known as a protostar. This phase can last for 100 000 years.
- Stars are formed from large clouds of gas and dust that collapse under their own gravity until they are dense enough for nuclear fusion to begin.
- When the protostar reaches a critical density, fusion begins and the star starts to shine. When the outward pressure from fusion balances the star’s gravity, it stabilises as a main sequence star.
- The core of the star heats as it contracts. This causes the material around the core to heat up until hydrogen fusion begins here.
- When the star runs out of hydrogen, this is the end of its ‘main sequence’ and it begins to swell out. Core contraction continues until it is hot enough for helium to fuse into carbon and oxygen.
- Stars the same size as our Sun (or smaller) swell out and cool down turning red. A red giant.
- When fusion stops no more radiation is released and the star collapses in on itself, this forms a ‘ White Dwarf’. This is smaller than it was before. Eventually it becomes cold forming a ‘Black Dwarf’.
🟢 Full Life Cycle of Stars with Huge Mass
- A large cloud of gas and dust contracts under its own gravity, heating as it goes, until it becomes a protostar.
- When the protostar is hot and dense enough, nuclear fusion begins. The star starts to shine and stabilises as a large main sequence star. A massive star might only remain like this for 10 million years.
- When core hydrogen runs out, nuclear fusion stops and core collapse begins. As with a small star, this heats up a surrounding shell of hydrogen, and shell hydrogen burning begins.
- When the core heats up further and core helium burning begins, the star expands into a Red Supergiant.
- When core helium runs out, the core collapse process starts again. This time it heats until a heavier element is ignited in a shell and in the core. This cycle continues until the star is ready to implode/collapse.
- Finally the star collapses extremely rapidly, creating a massive shockwave that blows the core apart in an explosion called a supernova.
- The explosion compresses the core of the star into a neutron star. This is an extremely dense object made up only of neutrons. If the star is massive enough, it become a black hole instead of a neutron star. The gravitational field of a black hole is so strong that nothing can escape from it. Not even light, or any other form of electromagnetic radiation.
🟢 Explain how atoms of the element helium (He) are formed in a star.
Light elements are formed from fusion stars. Stars such as the Sun fuse hydrogen nuclei (i.e, protons) into helium and similar small nuclei.
🟢 Explain his atoms of very heavy elements, such as gold (Au), were formed.
Heavy elements are formed when a massive star collapses then explodes as a supernova. The enormous force of the collapse fuses small nuclei into nuclei bigger than the iron nuclei, like gold for example. The explosion scatters the elemhts throughout the universe.
🟢 Explain how, and when, atoms of different elements may be distributed throughout the Universe
The debris from a supernova contains all the known elements, from the lightest to the heaviest. Eventually, new stars form as gravity pulled the debris together. Planets form from debris surroundings a new star. Because of this, planets will be made up of all the known elements too.
🟢 Describe what happens to a star much bigger than the Sun, once the star reaches the end of the ‘main sequence’ period of its life cycle.
Once the main sequency period ends, the star begins to collapse in on itself as there is no more radiation as an outwards to counteract the gravity as the inwards force. This makes it hot enough to fuse atoms, which causes the star to grow much larger, and into a Red Supergiant. This cycle continues with the star fusing new and heavier elements until iron is formed. Iron cannit be fused, as the star doesn’t have enough energy, so the star collapses and explodes in a supernova. Most stars will then become a neutron star, but the largest will form a black hole.
🟢 What does the Sun orbit
The Sun orbis the centre of the Milky Way
🟢 Differences and a Similarity between the Moon and a Satellite
Similarity:
Both orbit the earth ane both a satellites
Moon:
- A Natural Satellite
- Occurs Naturally
Satellite:
- Man-Made Satellite
- Put into space by man
🟢 What is a satellite?
A satellite is anything that orbits a celestial body (star, planet, moon etc).
Both natural and artificial satellites exist.
🟢 What do we use satellites for?
Satellites are used for GPS systems, messaging, TV, space exploration and many other things
🟢 How does the Moon Orbit the Earth, the Earth orbit the Sun, and other planets orbit the Sun
Moon Orbiting the Earth:
Circular Orbit
Earth Orbiting the Sun:
Circular Orbit
Other Planets Orbiting the Sun:
Elliptical Orbit
