Astrophysics Flashcards
What is a satelite?
Objects that orbit around larger objects in space.
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What is the order of the planets from closest to the sun to farthest?
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
What is the relationship between the radius of a planet/satelite’s orbit and its speed?
They are inversley proportional due to gravity.
- As the radius of the orbit increaces, it’s speed decreaces as there is less of a gravitational pull, because it is further away..
- As the radius of the orbit decreaces, it’s speed increaces as there is more of a gravitational pull, because it is closer.
Explain the life cycle of a star of our sun’s size.
(6 marks)
- large amounts of dust and gas called nebulae compile together. due to the forces of gravity, they eventually collapse in to form a protostar.
- due to the protostar’s gravity, it attracts more clusters of dust and gas. this enlargens it, and increaces it’s mass and subsequently its force of gravity.
- as the particles of hydrogen gas collapse in, they collide. this collision causes nuclear fusion, which produces helium.
- The force of gravity pulling inwards, and the force of nuclear fusion pulling outwards now forms a main sequence star. stars remain in this life stage for billions of years.
- At this point, stars of the same size as our sun, and stars bigger than our sun go through two different life cycles.
- If a star is a similar size to our sun, it will eventually run out of hydrogen for nuclear fusion. at this point the force of gravity pulling inwards is greater than the fusion force pulling outwards. This forms a red giant.
- The red giant fuses helium to sustain itself. Eventually the helium runs out. The force of gravity now overtakes the force of fusion (as no more fusion can occur) and the star collapses in to form a smaller, dense white dwarf.
- This white dwarf is the remainder of the hot core of the star. It still emits light and heat. This white dwarf eventually cools down to form a black dwarf. The black dwarf emits no light and no heat.
Explain the life cycle of a star larger than our sun.
- nebulae (clusters of dust and gas) collapse in together due to the force of gravity. This forms a protostar.
- the protostar attracts more dust and gas due to its force. the hydrogen gas atoms begins to collide together and undergo nuclear fusion. this produces helium, and means it has now become a main sequence star.
- after billions of years, the star will eventually run out of hydrogen. helium is now being used for fusion, and it fuses to produce denser elements. The most dense of these being iron. This is the red supergiant stage.
- At some point, the star will stop undergoing nuclear fusion. After several cycles of expansion and contraction, the star undergoes a supernova explosion.
- This explosion leads to elements heavier than iron being formed, and they get ejected across the universe.
- If the star was quite big, it will collapse to form a neutron star.
- If the star was massive, it may collapse in to form a black hole. This black hole is so dense, that it pulls in any light that comes in it’s way.
Why do some galaxies appear to be red-ish from earth?
- Galaxies that have a greater red-shift are moving away from earth.
- Because they are moving away, they emit longer wavelength/lower frequency radiation, and the longest wavelength of visible light is red.
- Red-shift is also used as proof that the universe is expanding, as the further away a galaxy is, the faster it seems to be moving away from us.
What does the big bang theory state?
The universe began from a small, hot dense region, then it exploded and expanded outwards. This expansion is still happening today.
What are two things about the universe that scientists do not fully understand yet?
- How the universe is expanding - some theorise dark energy causes it to expand.
- What the universe is mainly composed of - some theorise that it’s dark matter which also holds galaxies together but doesn’t emit electromagnetic radiation.
