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Galaxies: one or many?
Aim: to investigate the work of
Edwin Hubble
What can we see?
When we look into the night sky we can
see many stars with our naked eye, we
see stars in our galaxy, the Milky Way.
Scientists believe the Milky Way is just
one of many galaxies. It is thought
there are hundreds of billions of
galaxies.
With the use of telescopes we have been
able to see fuzzy-looking things objects
that look bigger than stars, there were
originally called nebulae.
It was found that a nebula was actually a
collection of stars, around a spherical
cloud, this idea changed the names of
nebulae to globular clusters.
Globular Cluster
What did Hubble do?
Hubble studied the
Andromeda Nebula
and spotted a
Cepheid star. So he
measured it’s
distance and realised
it was almost
1,000,000 light years
away. Much bigger
than the dimensions
of the Milky Way.
Hubble’s find made him mourned as an
astronomer, and the Hubble Space
Telescope was named after him.
As the distance between galaxies is up to
13-14 thousand million light years apart,
astronomers use the units;
1Mpc = 1 million parsecs
In the 1920’s
A lot of work in astronomy was happening a
lot of Cepheid stars had been recognised.
Hubble used Henrietta
Leavitt’s discoveries to
determine the distance of
many galaxies. While doing this
he made a massive discovery,
that galaxies were receding
(moving away)
The Hubble Constant
It turned out that the further the distant the
galaxy the faster it is moving away.
Hubble’s graph shows that.
Hubble constant shows the speed of
recession.
Speed of recession = Hubble constant x distance