Resulting Structures of Galactic Collisions :: Essays Papers

Resulting Structures of Galactic Collisions In the visible universe, there is one type of event that is often responsible for a good deal of the varied phenomena we observe across the cosmos. A type of event whose effects are both destructive and creative. This event is the interaction of two or more galaxies. The results of a galactic interaction are so varied that each event is unique. Therefore, only a select few examples will be described in the following pages. An examination of the term â€Å"galactic interaction† does not immediately convey much in the way of understanding as to exactly what happens during one of these events. The problem is that the word â€Å"interaction† is fairly ambiguous, yet it must be so because two galaxies can interact in so many ways that literally every interaction we observe is a unique event (depending on how close one looks at the details). Changing the mass ratios, the angle of impact, or the morphological type of the progenitor galaxies can greatly influence the nature of the system after the interaction has played itself out, as we shall see. However, galactic interactions do often share many characteristics. The most notable feature associated with interacting galaxies is often the â€Å"starburst† phenomenon. A starburst is an extremely high rate of star formation over part or all of a galaxy over a cosmologically short period of time (possibly a few billion years as opposed to several billion years). Galaxy interactions cause gravitational instabilities in interstellar gas clouds, which compress the gas in the clouds and trigger star formation (Mouri 2003). When astronomers look at an ongoing starburst in a distant galaxy, they see the starburst as a bluer region than the surrounding parts of the host galaxy. That is due to the extremely hot and energetic, yet short lived, O-type stars produced in the burst, which outshine all of the other stars being born around them as well as the older, redder stars that populate the galaxy. For an example of a galaxy undergoing an interaction- induced starburst, let us look at M82, a member of a nearby group of galaxies. M82 is a rather disturbed-looking disk galaxy that is currently undergoing a massive amount of star formation in its nuclear region. The cause is theorized to be a close encounter between M82 and M81, its large neighbor, which occurred about a billion years ago (Lipscy & Plavchan 2003).