Star Astronomy

There are many different shapes and sizes of star galaxies. An elliptical galaxy is an oval egg shaped galaxy, there are also circular galaxies and spirals which are similar to a pin-wheel in shape. Star galaxies which have none of these shapes and known as irregulars. The stars within a galaxy remains together due to gravitational forces, planet earth is part of the Milky Way galaxy which has over one hundred billion other stars, including the sun within it.

Until the early twentieth century astronomers did not realise that there were other galaxies other than the Milky Way. When they looked through their telescopes they observed blurred patches in the sky which they called nebula and believed that these were part of the Milky Way. Further observations and studies carried out by Edwin Hubble discovered that the nebulas were in fact full of billions of stars which were also held together by gravity and it is now known that the Milky Way is just one galaxy among billions in the universe.

Star galaxies are made up from gases, dust and millions of stars which have different shapes such as the disc shaped Milky Way, which is included in a group of galaxies known as the Local Cluster. The disc of the Milky Way is one hundred times longer that it is deep, Spiral and Galactic galaxies are relatively thin and dense which rotate extremely fast.

Giant elliptical galaxies are the largest galaxies in the sky. They are made up of old stars and have very little or no dust in them. The elliptical galaxies which have been probed all have massive black holes in their centre, they do not have disks around them and more regularly found in the most crowded parts of the universe. Astronomers widely accept that the elliptical star galaxies are formed from the merger of smaller galaxies and have found that some of the mergers can be very violent with galaxies colliding together at speeds of over one million miles per hour!

When the star galaxies begin to merge the stars and dark matter in each become affected by the approaching galaxy and during the later stages of the merger the shape of the galaxy begins to change very rapidly due to the stars being affected by the gravitational forces. The complexities of these galaxy mergers changes the shape and size of the galaxies which are colliding as the ordered motion of the stars is transformed into random energy, giving elliptical galaxies stars which are on unordered orbits.