P2 - Space (Done) Flashcards
What is the first stage in a stars life cycle ?
They initially form from a cloud of dust and gas called a nebula, the force of gravity pulling this together to form a protostar.
What happens to the star to evolve from a protostar ?
As it gets denser the temperature rises and more particles collide, when the temperature is high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei - giving out lots of energy, heating the core of the star.
What is a main sequence star ?
The stage after a protostar, a long stable period where outward pressure, caused by nuclear fusion, that tries to expand the star balances the force of gravity - lasting several billion years.
What happens to a main sequence star at the end of its stable period ?
The hydrogen begins to run out and it then swells into a red giant or a red super giant if its a bigger star, it’s red because the surface cools. Fusion of helium and other elements occurs forming heavier elements (up to iron) in the core.
What happens to the smaller stars after they’ve become red giants ?
They become unstable and eject the outer layer of dust and gas leaving behind a hot dense solid core - a white dwarf.
What eventually happens to white dwarfs ?
As it cools it emits less energy, and at the point where it no longer emits a significant amount it’s called a black dwarf.
What happens to bigger stars after they’ve become red super giants ?
They start to glow brightly again undergoing more fusion, and expand and contract several times forming elements as heavy as iron, eventually exploding in a supernova. This forms elements heavier than iron and ejects them into the universe to form new planets and stars.
What happens to the remains of a star after the supernova ?
The supernova ejects the outer layers only, leaving a very dense core called a neutron star. If it is massive enough it will become a black hole.
What is a black hole ?
A super dense point in space that not even light can escape from.
How do stars contribute to the universe ?
Their life cycle produce and distribute all the naturally occurring elements into the universe as building blocks for planets and stars.
What is the sun ?
It is a main sequence star, half way through this stable period. It is also a small to medium sized star.
What is in our solar system ?
The sun is at the centre and is orbited by eight planets and many other objects.
What classifies as a planet ?
Large objects that orbit a star, and large enough to clear their neighbourhoods - strong enough gravity to have pulled in any nearby non-satellite objects.
What are dwarf planets ?
Such as pluto - planet-like objects that orbit stars but don’t meet all the rules for being a planet.
What is a moon ?
They orbit planets and are a type of naturally occurring satellite.
