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19 Cards in this Set

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  • Back

What’s in the solar system?

-sun is at centre of solar system

-8 planets orbit the sun+ 1 dwarf planet (Pluto)

-natural satellites


Celestial body that orbits a planet either natural (moon) or artificial (communications)

How was the sun formed ?

Formed from a cloud of dust and gas (nebula) pulled together by gravitational attraction

Dwarf planet

Object orbiting a star that is massive enough to be rounded by gravity

-but has not ‘cleared the neighbourhood’


Rock in space that orbits the sun but some may cross the earths orbit producing a risk of collision.


A ball of icy rock that follows an elliptical orbit around sun.

-vaporises as it approaches the sun turning it into a gas.

Life cycle of a star

Nebula>Protostar>main sequence star


As the mass falls together it gets hot. A star is formed when a hydrogen nuclei fuse together to make helium

Red giant star

The hydrogen has been used up in the process. Larger nuclei begin to form and star may expand to become a red giant.

White dwarf

Star may begin to contract under the pull of gravity. The star becomes a white dwarf which fades and changes colour as it cools.

White dwarf

Star may begin to contract under the pull of gravity. The star becomes a white dwarf which fades and changes colour as it cools.


Larger star with more mass will go on making nuclear reactions, getting hotter and expanding until it explodes .

Main sequence star criteria

-forced caused by gravitational attraction and fusion energy are balanced

-radiation pressure from fusion reactions tend to expand the star

-gravitational attraction tends to collapse the star

What does a supernova do?

When it explodes, all the elements produced are thrown out into the universe.

What must happen for a stable orbit?

The radius must change if the speed changes.

How do planets stay in orbit?

Gravitational attraction provides the centripetal force needed to keep planets and all types of satellite in orbit.

Red shift

The increase in the wavelength of light from most distant galaxies.

The further away a galaxy, the faster they are moving and the bigger observed increase in wavelength

What suggests there is an expanding universe?

The change of each galaxy’s speed with distance

Big bang

The starting point of the expanding universe when it was smaller and more dense