Cosmology

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What is the Definition of the Astronomical Unit (AU) ?
One Astronomical unit is the average distance between the earth and the sun(1.5x10^15)
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What is the Definition of a Light Year (ly) ?
1 Light year is the distance Light travels in 1 year.
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What is the Definition of a Parsec ?
An object at a distance of 1 parsec has an angle of parallax of 1 arc sec with the earth.
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What are the 3 key features of the cosmological Principle ?
On a large scale the universe is: homogeneous, isotropic and the Laws of Physics are universal
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What is the Definition of a planet?
An object in orbit around a star which: mass large enough to create its own gravity to become round, no Fusion and cleared orbit of other objects.
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What is the Definition of a Planetary Satellite?
A body in orbit around a planet,( includes moons and man-made satellites)
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What is the Definition of a comet?
Small irregular bodies made up of ice,dust and small pieces of rock.
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What is the Definition of a Galaxy?
A collection of stars, interstellar dust and gas.
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What does a star originate from?
A cloud of interstellar dust and gas with denser clumps which contract under the force of gravity.
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What is a Protostar?
Protostars are the clumps of Dust and gas which gather together through gravity.
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How does a Protostar develop in to a main sequence star?
Protostar contracts in till the temp at the center is a few million degrees. Hydrogen nuclei fuse to form helium under this heat. Gas pressure increases due to temp increase and volume decrease. Radiation pressure increases due to fusion.
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Why does a Main Sequence star become Red Giants?
Star runs out of Hydrogen fuel which means Fusion stops. Fusion creates radiation pressure which stops the star from collapsing.
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How is a White Dwarf made?
Low mass stars eject their helium shells to leave stable dense core behind. Has to be under 1.4 times the mass of the sun.
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What happens to Massive stars after the Main Sequence?
Becomes a super Red Giant due to more shell layers made. The star will then keep contracting and a Supernova will occur.
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What is produced after a Supernova?
Either a Black Hole or Neutron star
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What is a Neutron Star?
Extremely dense stars which are typically very small. produced from a supernova.
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What is a Black Hole?
If the mass of star is more than x3 of sun the neutrons can't hold the gravitational forces and collapse. Up to a certain distance away the gravitational pull is so great light cant even escape.
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What is Luminosity?
The measure of how bright an object is.
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What is the Big Bang Theory?
The theory that the universe started off very hot and dense and has been expanding ever since
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Card 2

Front

What is the Definition of a Light Year (ly) ?

Back

1 Light year is the distance Light travels in 1 year.

Card 3

Front

What is the Definition of a Parsec ?

Back

Preview of the front of card 3

Card 4

Front

What are the 3 key features of the cosmological Principle ?

Back

Preview of the front of card 4

Card 5

Front

What is the Definition of a planet?

Back

Preview of the front of card 5
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