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 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