(8) Space Physics Flashcards
What are the components of our solar system?
The sun (star), the eight planets and dwarf planets that orbit it and moons
What is a natural satellite?
Moons
What galaxy are we in?
Our solar system is a small part of the Milky Way galaxy
Describe the formation of a star:
1) cloud of gas and dust (nebula) are pulled together by gravitational attraction
2) this becomes more and more condensed and forms a protostar
3) as the protostar becomes denser the particles speed up and collide more. This increases the temperature and transfers energy from the GPE store to the thermal store
4) when the star is hot enough, fusion takes place of hydrogen atoms into helium nuclei. More energy is released and the star is so hot it starts to shine
5) it’s now a main sequence star (the main point of its life)
Describe the life cycle of stars the same size as our sun:
1) the nebula condenses
2) protostar is formed and becomes denser
3) fusion of helium (from hydrogen) takes place, main sequence star
4) hydrogen runs out in the core so it collapses and swells forming a red giant, now heavier elements start to form from helium
5) when there is no more light elements fusion stops and the star collapses in on itself (due to gravity) it becomes a white dwarf. This is much smaller, denser and hotter
6) it cools and becomes a black dwarf
Describe the life cycle of stars much bigger than our sun:
1) the nebula condenses
2) protostar is formed and becomes denser
3) fusion of helium (from hydrogen) takes place, main sequence star
4) hydrogen runs out in the core so it collapses and swells forming a red supergiant, now much heavier elements start to form from helium
5) the star collapses, the matter around the core compresses more and more
6) the compression suddenly reverses in a cataclysmic explosion called a supernova
7) the explosion compresses the core into a neutron star, an extremely dense object made only of neutrons
8) if the star is massive enough it will be in a black hole
How does fusion form elements?
Fusion in stars produces all of the naturally occurring elements. Elements heavier than iron are produced in supernovas and are scattered across the universe, the debris from a supernova contains all the known elements.
How do planets contain elements?
Eventually new stars will form as gravity pulls the debris together (from a supernova). Planets form from debris surrounding the star, because of this the planets contain these heavier elements
What is a black hole?
The gravitational field of a black hole is so strong that nothing can escape from it, not light or any other form of electromagnetic radiation
How long does a star stay in the main sequence stage?
Millions of years.
The star is stable because gravity acts inwards and the radiation from nuclear fusion in the core acts outwards. They are on equilibrium until the hydrogen is used up.
What force allows planets and satellites to orbit?
Gravity allows them to maintain the circular orbit. This is a centripetal force as the force of gravity is towards the centre of the orbit.
How does gravity impact direction and velocity of a satellite in orbit?
The direction of the satellites velocity is changed but the speed doesn’t change. It’s accelerating but not getting faster. (Circular orbit)
The direction of motion of any planet in a circular orbit is at a right angle to the direction of the force of gravity acting on it. No work is done.
What are the differences between elliptical orbits and a circular orbits?
A satellite in a circular orbit moves around the earth at a constant height above the surface, the speed stays the same even if velocity changes.
In an elliptical orbit it gets faster as it gets closer to the earth.
Give an example of a circular orbiting satellite:
Communication or GPS satellites move above the equator with a period of 24 hours. They stay above the same place (geostationary).
Give an example of an elliptical orbiting satellite:
Reconnaissance and weather
