Spiral Galaxy:
NASA Hubble Space Telescope recently shared a stunning video of a spiral galaxy known as Caldwell 45, or NGC 5248.
- Spiral galaxies are twisted collections of stars and gas that often have beautiful shapes and are made up of hot, young stars.
- In a spiral galaxy, the stars, gas, and dust are gathered in spiral arms that spread outward from the galaxy’s center.
- Most of the galaxies that scientists have discovered so far are spiral galaxies, as opposed to the other two main categories of galaxy shapes—elliptical and irregular.
- Approximately 60% of all galaxies are thought to be spiral galaxies.
- The Milky Way, the galaxy that includes Earth and our solar system, is an example of a spiral galaxy.
- Most spiral galaxies contain a central bulge surrounded by a flat, rotating disk of stars.
- The bulge in the center is made up of older, dimmer stars and is thought to contain a supermassive black hole.
- Approximately two-thirds of spiral galaxies also contain a bar structure through their center, as does the Milky Way.
- The disk of stars orbiting the bulge separates into arms that circle the galaxy.
- These spiral arms contain a wealth of gas and dust and younger stars that shine brightly before their quick demise.
- The majority of spiral galaxies rotate in the sense that the arms trail the direction of the spin.
- The visible portion of spiral galaxies contains only a small fraction of the total mass of the galaxy, and that spiral galaxies are surrounded by an extensive halo consisting mostly of dark matter.
- Spiral galaxies are thought to evolve into elliptical galaxies as the spirals get older.
