Galaxies

Galaxies Galaxies – large groupings of stars in space Contain more than a trillion stars (estimation based on size and brightness)

Types of Galaxies Spiral galaxies Elliptical galaxies Irregular galaxies

Spiral galaxies Bulge at the center and very distinctive spiral arms When the center has a bar shape, its a barrel spiral Milky Way galaxy is thought to be a spiral galaxy, similar to the nearest galaxy, Andromeda Our solar system is located on the outer edge

Elliptical galaxies Very bright centers and very little dust and gas Contain very old stars, no new stars forming

Irregular galaxies Galaxies that don't fit into any other class EX: Large Magellanic Cloud, companion to a large spiral galaxy whose gravity may be distorting the shape of their smaller neighbor

Contents of Galaxies Gas clouds – nebula Open clusters – groups of stars that form when large amounts of gas and dust came together located along spiral disk of a galaxy Newly formed open clusters have many bright blue stars Globular clusters – groups of older stars that formed from a large gas cloud Looks like a ball of stars Located in the spherical halo that surrounds spiral galaxies

Origin of galaxies Galaxies form from collapsing clouds of gas and dust If stars form slowly, the cloud collapses into a disk and forms a spiral galaxy If stars form quickly, the cloud becomes an elliptical galaxy

Back in time Looking through a telescope is like looking back in time because it takes time for light to travel through space Quasars – star like source of light/radio waves that is extremely far away