Space Flashcards
What do clouds of dust and gas come together to form? What force pulls them?
A protostar. Gravitational forces pull them.
What happens to a protostar?
It becomes denser and the nuclei of hydrogen atoms and other light elements start to fuse. The core gets hotter and brighter.
Why do stars radiate energy?
Because of hydrogen fusion in the core.
Why is a stable star stable? What type of star is this?
Because the inward force of gravity is balanced by the outward force of radiation from the core. It is called a main sequence star.
What happens to objects that are too small to become stars?
They can be attracted by a protostar to become planets.
What happens to stars of similar size to the Sun when they start to die?
They become red giants. Helium and other light elements fuse and form heavier elements.
What happens when fusion stops in a star similar in size to the Sun?
It contracts to form a white dwarf. Eventually, no light is emitted and it becomes a black dwarf.
What happens to stars much larger than the Sun when the start to die?
They swell to become red supergiants, which then collapse. It eventually explodes in a supernova.
When are elements heavier than iron formed in large stars? Why?
In the final stages of the life of the star because the process requires the input of so much energy.
What happens during the final stages of life of a big star?
All the elements are distributed through space by the supernova explosion. The outer layers are thrown into space. The core is left as a neutron star. If the is massive enough, a black hole is formed.
What is special about the gravitational field strength of a black hole?
It is so strong that not even light can escape it.
What happens with speed and velocity with an orbiting object?
Its speed is constant but it is always changing direction, so its velocity is continually changing.
What does a satellite accelerate towards?
The centre of the orbit.
What is the velocity of an orbiting object always perpendicular to?
The direction of the gravitational force.
What is the force needed to keep an object moving in a circle called?
The centripetal force.
Why does the centripetal force produce an acceleration?
Because it is a resultant force.
What happens to the speed of an orbiting object when distance to the larger object decreases?
The speed increases.
For an object to remain in Earth’s orbit it must:
Travel at a particular speed. Too great a speed and it will fly off into space. Too small a speed and it will fall down to Earth.
What is a galaxy?
A large collection of stars.
What does light observed from distant galaxies undergo?
Red-shift.
How does red-shift occur?
The frequency has decreased and the wavelength has increased. The spectrum of light is therefore shifted towards the red part.
What does red-shift show?
The galaxy is moving away from us.
What would blue-shift indicate?
That a galaxy is moving towards us.
How does red-shift vary between galaxies?
The further away the galaxy, the bigger the red-shift. We know that most distant galaxies are moving the fastest.
All distant galaxies are moving away from each other, so:
The whole universe is expanding.
What happened to gamma radiation during the Big Bang?
High-energy radiation would have become lower-energy radiation.
What is the radiation produced by the Big Bang called?
Cosmic microwave background radiation (CMBR).
What is the missing mass in the universe, not from stars called?
Dark matter.
What may happen to the universe, depending on density?
If the density of the universe is less than a particular amount, it will expand forever - the Big Yawn.
If the density of the universe is more than a particular amount, it will stop expanding and go into reverse - the Big Crunch.
