Galaxies can and do merge. In the past, collisions were more common when the universe was smaller and the islands of stars kept closer quarters. While mergers are less frequent today, they still do occur. Right now, our own galaxy, the Milky Way, is consuming the Sagittarius dwarf elliptical galaxy. But in about two billion years the Milky Way will have the tables turned on it, as the giant Andromeda Galaxy devours us.
For the 18th anniversary of the launch of the Hubble Space Telescope, 59 new images have been released, more than any other at one time. These images are all of some of the most spectacular events in the universe, galaxy collisions. Here is a look at a few of those images.
Colliding Galaxies Arp 148
Arp 148 looks straight out of a sci-fi movie. One galactic disk seen edge-on is puncturing another galactic disk at its center, seen face-on. The blue ring is a shockwave of material that was thrown outward after the collision. Arp 148 is still in the midst of colliding. Arp 148, also nicknamed Mayall's object, can be found 500 million light-years away in the direction of the constellation Ursa Major.
Tidal Interactions in Arp 240, or NGC 5257 and NGC 5258
The galaxies cataloged as Arp 240, or NGC 5257 and NGC 5258, are in the beginning stages of collision. These spiral galaxies, which are similar in mass and size, are being drawn together by their massive gravities. A stream of stars form a bridge between the two as they slowly twirl together. New stars are forming in each of their galactic disks. The pair lies about 300 million light-years away in the direction of the constellation Virgo. Except for a few points of light that are stars in our Milky Way Galaxy, nearly every other object in this image is a distant galaxy.
ZW II 96 and Star Formation
ZW II 96 is a good example of star formation that occurs during galactic mergers. As the dust and gas from each galaxy collides, new stars are formed. The star formation is seen as bright blue collections of light. In ZW II 96, threads of new star forming groups can be seen strung between the interacting galaxies. This collision of galaxies is found 500 million light-years away in the direction of the constellation Delphinus the Dolphin.
Merged Galaxy NGC 1614
NGC 1614 shows clear evidence of a galactic collision in its past. While the galaxy has some typical spiral shaping, it also shows tidal interactions that have tugged at it, resulting in the large sweeping arm and the tail that sticks straight out from the nucleus. NGC 1614 is located about 200 million light-years away in the direction of the constellation Eridanus.
More information on colliding galaxies and the whole collection of the 59 new images can be found at the European Home Page for the NASA/ESA Hubble Space Telescope.
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