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Measuring the Universe
· One astronomical unit is the distance from
the earth to the sun ­ 1.5*1011m
· A light year is the distance travelled by light in
a year. Worked out by multiplying the speed
of light by the number of seconds in a year ­
· For distances between starts and galaxies,
parsecs are used.…read more

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· This is measured using parallax ­ the angle
through which stars appear to move when
observed at different times during the year,
due to earths orbit.
· Parallax angles are so small that they are
measured in arc seconds ­ 1 arc second is
1/3600th of a degree.
· A parsec is defined as the distance to a star
that gives a parallax angle of 1 arc second ­
3.1*1016m.…read more

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Formation of stars
· Slightly denser areas of the universe have a
slightly higher gravitational pull.
· This pulls in material, making it denser and
giving it a greater gravitational pull, so it pulls
in more material etc.
· This process is known as gravitational
· As it collapses it becomes hotter because it is
losing potential energy and gaining kinetic
energy (which is directly proportional to
temperature).…read more

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Formation of stars
· This ball of gas and dust is known as a protostar.
· Eventually the core of the material becomes hot
enough for hydrogen fusion to take place forming
helium nuclei. This process is called hydrogen
· The fusion creates radiation pressure which
balances out the gravitational force.
· Once they are equal the star will stop collapsing and
continue to burn for millions of years. It is now
called a main sequence star.…read more

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thank you for sharing! :)

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