5 Fascinating Facts About Galaxies

The Milky Way Galaxy is where we will call home, but there are billions upon billions of other galaxies across the universe, displaying a wide range of characteristics and features, and undergoing all sorts of interactions and evolutions. If you want to learn a bit more about galaxies, you can take a look at the following 5 facts to get started.

5 Interesting Facts About Galaxies You May Not Know

1. Three Main Types of Galaxies: There are three main types of galaxies, the spiral galaxy which has a flat disk, spiral arms and a central bulge; the elliptical galaxy which has no disk or arms; and the irregular galaxy which has no real visible structure. There are many other more specific classifications as well, for example there are barred spiral galaxies.

2. Spiral Arms Aren't True Structure: The spiral arms we see on so many galaxies, including our own Milky Way, aren't true examples of structure. Instead they are density waves that constantly are changing, always being formed and re-formed. You can think about the spiral arms of a galaxy as a traffic jam. Stars moving at normal speed get caught in a more dense area of stars, slow down as a result, and then appear as visibility present areas of matter, before speeding up again on their way out of the area.

3. Active Galaxies: Active galaxies release huge portions of energy at scales that even our own large Milky Way can't compete with. This energy release is caused by the supermassive black holes in their centers. Seyfert galaxies have a nucleus that can release 10,000 times more energy than our entire galaxy, with the majority of that energy being in the infrared wavelength. Radio galaxies release huge portions of energy at radio wavelengths, forming massive emission lobes at each side. From lobe to lobe, these galaxies and their energy missions are 10 times the size of the Milky Way.

4. Quasars: The most luminous objects in the universe are quasars, which are the bright center of certain very distant active galaxies. They are the farthest known objects in the universe in some cases, with the most distant being discovered at 13.7 billion light years away, which is the extent of our visible universe to this time. A result of energy emission from galaxy collisions and formation, quasars stopped appearing about 10 billion years ago.

5. Galaxies Collide: Galaxies are constantly in a state of flux, interacting with other galaxies through collisions and mergers. Even our own Milky Way is on a several billion year collision course with our biggest neighbor, Andromeda. Don't worry though, even as galaxies collide and merge, individual stars and systems escape untouched. This is because the distance between stars is absolutely massive, enabling them all to pass through the space around each other.

Source: Chaisson and McMillan, Astronomy Today, Sixth Edition. 2008.