Topic 8 - Space Flashcards
Describe the life cycle of a star smaller than or the same size as our Sun.
A star is formed from a nebula. The gravity pulls it together to form a protostar, which gets heavier as particles collide and the star gets denser. Eventually it gets so hot that nuclear fission creates helium from hydrogen which gives out so much energy that it keeps the star’s core hot. There is a stable period where the force of the fusion keeps the star from collapsing under the force of gravity. This is a main sequence star. When the hydrogen runs out, it swells into a red giant (red means the surface is cooling). More fusion occurs and heavier elements such as iron are created. When it becomes unstable the dust surface is ejected and a white dwarf is left. As it cools it loses its colour and becomes a black dwarf.
Describe the life cycle of a star larger than our Sun.
A star is formed from a nebula. The gravity pulls it together to form a protostar, which gets heavier as particles collide and the star gets denser. Eventually it gets so hot that nuclear fission creates helium from hydrogen which gives out so much energy that it keeps the star’s core hot. There is a stable period where the force of the fusion keeps the star from collapsing under the force of gravity. This is a main sequence star. It then becomes a red super giant. More fusion occurs and heavier elements such as iron are created. They then expand and contract several times because of varying nuclear reactions before exploding in a supernova and creating elements heavier than iron. This forms new planets and stars. This leaves a dense core called a neutron star, and if the star is large enough it becomes a black hole.
Name 4 satellites that orbit our Sun.
1) Planets
2) Moons that orbit the planets (natural satellites)
3) Dwarf planets
4) Artificial satellites
Which galaxy are we in?
The Milky Way.
How does an orbit work in detail? (Hint - A and G)
We travel in an elliptical orbit around the Sun. We constantly accelerate because we are constantly changing direction, but we don’t constantly gain speed. The force causing acceleration is towards the centre of orbit. Gravity means we should fall in, but instantaneous velocity (at a right angle to the acceleration) keeps us in a circle. (Please also check the book)
Why does the size of an orbit depend on the orbital speed?
The force closer to a star (for example) is greater. This means that objects close to it must travel faster to stay in orbit and avoid crashing into it or floating away. For a stable orbit, slower moving objects must be further away whilst faster moving objects must be closer.
What is red-shift and how does it prove that the universe is expanding?
Wavelengths of light from different galaxies are longer than they should be and are shifted to the red end of the spectrum (red-shift). This suggests that galaxies are receding away from us, and more distant galaxies are moving away faster than closer ones. The only conclusion is that the universe is expanding.
Describe the ‘Big Bang’ and how it links to red-shift.
First the universe was very dense and compacted into a small space. Then an ‘explosion’ happened, known as the Big Bang. This ‘explosion’ was space expanding, which is still happening now.
What do scientists currently think the universe is made of?
Dark matter and dark energy.
Why might the theories we have about space change?
We still don’t know a lot, so if we observe new evidence we need to adapt our theories. Currently, the Big Bang theory is the most accurate of how our universe begun and is expanding that we have based on the evidence we have.
