Interacting galaxy
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Interacting galaxies (Colliding galaxies) are the result of one galaxy's gravity disturbing another galaxy. An example of minor interaction is a satellite galaxy disturbing the primary galaxy's spiral arms. An example of major interaction is a galactic collision.
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[edit] Satellite interaction
.jpg/240px-Whirlpool_(M51).jpg)
A giant galaxy interacting with its satellites is common. A satellite's gravity could attract one of the primary's spiral arms. Or even the satellite could dive in to the primary (e.g. Sagittarius Dwarf Elliptical Galaxy). This could trigger a small amount of star formation. The satellite could be a vacuum cleaner and suck up some of its primary's stars or vice versa.
[edit] Galaxy collision
Colliding galaxies are common in galaxy evolution. Due to the extremely tenuous distribution of matter in galaxies, these are not collisions in the normal sense of the word, but rather gravitational interaction. Colliding may lead to merging. This occurs when two galaxies collide and do not have enough momentum to continue traveling after the collision. Instead, they fall back into each other and eventually merge after many passes through each other, forming one galaxy. If one of the colliding galaxies is much larger than the other, it will remain largely intact after the merger; that is, the larger galaxy will look much the same while the smaller galaxy will be stripped apart and become part of the larger galaxy. Through-passes are less disruptive of galaxy shapes than mergers in that both galaxies largely retain their material and shape after the pass.
[edit] Galactic cannibalism
Galactic cannibalism refers to the process by which a large galaxy, through tidal gravitational interactions with a companion, merges with that companion, resulting in a larger, often irregular galaxy.
The most common result of the gravitational merger of two or more galaxies is an irregular galaxy of one form or another, although elliptical galaxies may also result.
It has been suggested that galactic cannibalism is currently occurring between the Milky Way and the Large and Small Magellanic Clouds. Streams of gravitationally-attracted hydrogen arcing from these dwarf galaxies to the Milky Way is taken as evidence for this theory.
[edit] Notable interacting galaxies
| Name | Type | Distance (million ly) |
Magnitude | Notes |
|---|---|---|---|---|
| Whirlpool Galaxy (M51) | SAc (SB0-a) | 37 | +8.4 | Satellite interacting with its primary |
| NGC 2207 and IC 2163 | SAc/SAbc | 114 | +11 | galaxies going through the first phase in galactic collision |
| Mice Galaxies (IC 819/20) |
S0/SB(s)ab | 300 | +13.5 | galaxies going through the second phase in galactic collision |
| NGC 1097 | SB(s)bc (E6) | 45 | +9.5 | Satellite interacting with its primary |
| Antennae Galaxies (NGC 4038/9) |
SAc/SBm | 68 | +10.3 | galaxies going through the third phase in galactic collision |
| NGC 520 | S | 100 | +11.3 | galaxies going through the third phase in galactic collision |
[edit] Future collision of the Milky Way Galaxy with the Andromeda Galaxy
Astronomers have estimated that our galaxy, the Milky Way galaxy, will collide with the Andromeda galaxy in about three billion years. It is thought that the two spiral galaxies will merge to become an elliptical galaxy.
[edit] See also
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