SOLAR SYSTEM; STABILITY OF ORBITAL MOTIONS; SATELLITES Flashcards
After the big bang the universe was filled with what type of gas?
Hydrogen gas, the lightest of the elements.
What is a moon?
A natural satellite that orbits a planet.
What is a galaxy?
A massive group of stars (hundreds of billions in milky way)
What do stars for from?
Clouds of gas and dust ( a nebula)
What is the main gas in a nebula?
Hydrogen
What is the first stage of a star forming?
Gravity causes the cloud of dust and gas to collapse, as the dust particles move faster the temp rises to millions of degrees Celsius
What is a protostar?
A collapsing cloud of hot gas and dust (due to gravity)
What happens to a protostar if the temperate gets high enough?
Nuclear Fusion-Hydrogen nuclei join together to form helium
After which stage has the protostar become a star?
After nuclear fusion.
Nuclear fusion releases…….
Nuclear fusion releases a huge amount of energy
What are the two opposing forces acting within the star?
Gravity is acting inwards and tends to make the star collapse. The energy from nuclear fusion creates a force acting outwards.
How do stars expand?
If the force of nuclear fusion pushing outwards is greater than the inward force of gravity.
When is a star at equilibrium?
When the force due to gravity is equal to the force due to nuclear fusion.
What happens when the amount of hydrogen in a star runs out?
The outward force due to fusion energy is less than the inward force due to gravity. Causing a star to collapse inwards
What happens to a star when it collapses inwards?
The temperature increases, so helium nuclei fuse together to form heavier elements
How are heavier elements formed in a star and what does this form?
(Main- sequence star)
In a main sequence star, after the hydrogen runs out helium nuclei fuse together to create heavier elements making the star expand to form a Red- Giant
How is a red-giant formed?
By helium nuclei fusing together to form heavier elements, making the star expand.
What happens to form a White Dwarf?
At some stage a red giant stops fusing helium so the star shrinks and forms a white dwarf.
Why do White Dwarfs gradually cool down?
Because the white dwarf is no longer carrying out fusion.
What happens when a white dwarf stops releasing any energy?
It becomes a black dwarf.
What is a main sequence star?
A star about the same size of our sun
What happens to a star much larger than the sun after running out of hydrogen?
The star expands and leaves the main sequence stage to form a Red Super Giant.
What happens in Red Super Giants
Helium nuclei fuse together to produce much heavier elements
Nuclear fusion cannot make elements heavier than….
Iron
