Considering how long it’s been since my last post, I felt that this entry needed to be truly stellar. The trouble was, in doing research, much of the most interesting material I came across regarding stars seemed to be made up.¹ That wouldn’t do. Then, with expectations flagging, I found it: galactic collisions. Galactic collisions make for beautiful pictures and take place on a massive, galaxy-shattering scale that can only be described by words like “epic,” “monumental,” and “holy shit!”² They also take an interesting variety of forms. Some galaxies dance peacefully together, ever so slightly avoiding actual collision. Others merge like lovers, taking all the metaphor out of the phrase “when two become one.” For other galaxies, their collisions are more akin to hit-and-run accidents, or even cannibalism.
The Whirlpool galaxy and its companion NGC 5195 are a wonderful example of cosmic dance. The little NGC 5195 has been passing alongside the Whirlpool galaxy for millions of years. The gravitational interaction of these two partners has likely had great effect on both, sharpening the larger’s two distinct spiral arms and contributing to the smaller’s own amorphous form.
More intimately, the Antennae galaxies have forgone mere dancing, to merge together in blissful, if fiery, harmony. Once, they were two independent spiral galaxies, but hundreds of millions of years of courtship has brought them together so that they are barely distinguishable from one another. A few hundred million years more may find them merged completely, but give them time; in cosmic terms, they’re a young couple yet.
Another young couple is the Mice galaxies. While they are expected to merge like the Antennae, the Mice are still in the less intense phase of their merge, still dancing around one another, interacting, but still relatively distinct, flirting with the idea of union.
In stark contrast to these lover galaxies is the Cartwheel galaxy, who looks like a hit-and-run victim. The Cartwheel’s distinctive ripple-in-a-pond look is the result of a nasty head-on collision with a smaller galaxy, which then continued on its merry way, leaving the Cartwheel galaxy to sort itself out alone.
On the flip side of the smaller galaxy’s David-versus-Goliath drubbing of the Cartwheel, is galactic cannibalism, which occurs when large galaxies devour their smaller companions whole or in part. This can be seen in the nearby Andromeda galaxy which has stripped stars from its satellites M32 and NGC 205. It even appears to be syphoning off stars from the Triangulum galaxy, from a distance of a million light-years.
The same can be seen in our own Milky Way galaxy, which has numerous star streams and clusters that could be the remnants of dwarf galaxies slowly being digested.
The cannibalism of Andromeda and the Milky Way may serve as a common interest when the two galaxies meet, as they are expected to, in a few billion years. Perhaps they will slam together merging themselves like the Antennae, or perhaps they will dance around each other for a time, merging slowly and cautiously like the Mice galaxies. One thing we can know for sure: it will be a love affair of astronomical proportions.
—
1. Many of the interesting and bizarre types of stars and stellar phenomenon, like fuzzballs* and Quark stars* are purely hypothetical, or in rare instances theoretically confirmed only by the scantiest of evidence. My favorite is the preon star, a hypothetical star made up of a hypothetical type of particle known as preons. Seems like someone would confirm the preon’s existence before pretending things can be made out of it.
2. Yes, I know “holy shit” is a phrase, not a word.
More Information/Sources:
http://blogs.discovermagazine.com/badastronomy/2009/10/13/the-beauty-of-cosmic-collisions/
http://csep10.phys.utk.edu/astr162/lect/galaxies/colliding.html
The Whirlpool:
http://www.spacetelescope.org/images/html/heic0506a.html
http://usproxy.bbc.com/2/hi/science/nature/1263664.stm
http://apod.nasa.gov/apod/ap090526.html
The Antennae:
http://www.nasa.gov/multimedia/imagegallery/image_feature_1086.html
http://www.spacetelescope.org/news/html/heic0615.html
http://www.spaceref.com/news/viewpr.html?pid=25413
The Mice:
http://hubblesite.org/newscenter/archive/releases/2002/11/image/d
http://www.daviddarling.info/encyclopedia/M/Mice.html
The Cartwheel:
http://hubblesite.org/newscenter/archive/releases/1995/02/
http://apod.nasa.gov/apod/ap010612.html
http://csep10.phys.utk.edu/astr162/lect/galaxies/Cartwheel.html
http://www.spacedaily.com/reports/Cartwheel_Galaxy_Makes_Waves_In_New_NASA_Image.html
Cannibalism, Andromeda, and Milky Way:
http://www.space.com/scienceastronomy/astronomy/andromeda_010705.html
http://www.newscientist.com/article/dn17728-milky-ways-twin-caught-dismembering-neighbour.html
http://www.newscientist.com/article/dn14549-eleven-new-streams-of-stars-found-in-milky-way.html
http://www.spacedaily.com/reports/Sloan_Survey_Identifies_New_Dwarf_Galaxy_Inside_Milky_Way.html
http://www.guardian.co.uk/science/2009/jan/05/galaxy-collision-space-milky-way
this article was great I mean i actually enjoyed reading this not just becuase im curious about space and stars but because of the way you wrote it actually made reading fun which for is notoriously boring
thanks bruv i hope you do more stuff on space and stars
Safe.