[Image: The Antennae galaxies, a pair of merging galaxies named for the long tidal tails of stars, gas, and dust ejected during the merger. In the next several hundred million years, the two galaxy nuclei seen here will combine to form a single merger-remnant galaxy. Credits: NOAO/AURA/NSF, B. Twardy, B. Twardy, and A. Block (NOAO)]
A few years ago, I watched a documentary on black holes and how pairs of them have been observed to dance, or rather waltz. What does this mean exactly? Allow me to explain.
Nearly every galaxy has a central black hole. Most of us are familiar with merging galaxies, right?! The reason galaxies merge is due to their central black holes. It has been observed that there are pairs of black holes that move towards each other in a choreographed way and will eventually collide.
Back in 2010, astronomers used the Deep Imaging Multi-Object Spectrograph (DEIMOS) on the 10-meter Keck II Telescope and discovered what they believe to be 33 pairs of black holes in distant galaxies. Although, not everyone agrees with this observation. Some believe what is really happening is that one of the black holes is recoiling and being kicked out of its galaxy. Either way, as Julia Comerford from the University of Texas at Austin explained, both hint at black holes merging. Astronomers all agreed that additional observations were necessary to distinguish between a "pre-merger waltz" or "post-merger recoil".
When I first heard about this on Through the Wormhole (Yes, with Morgan Freeman!!), I was quick to read up about it a bit. I even read (I recall in the UCR news but can't seem to find the article!!) that many elliptical galaxies have black holes at their center as well.
This is all very cool, I know. :) Even more so, there is still so much to be understood about black holes! All this leaves me with so many questions. Specifically, one question that comes to mind, was there or could there have been an elliptical/spiral black hole pair? (I don't see why not. This would have had to occur during a specific time frame.) Also, it makes me think of galaxies without central black holes. Almost seems kind of strange. What do you think?
Below are a few links that I thought some of you, dear readers, would be interesting in clicking on. Please take a special peek. You can even look after finals. :P
Galaxy collisions take a lesson from dance by Julia Comerford
Black Holes by Professor Wudka
Gargantuan Black Hole Occupies Modest Galaxy
So the reason that galaxies merge is not because of the black holes. The gravity from the black holes only dominates over the galaxy in an extremely small region in the center. A central black hole might have 10^8 solar masses but there is 3-4 orders of magnitude more mass in stars (and even more in dark matter).
ReplyDeleteBut yes, when the galaxies merge, the black holes should eventually find themselves very close to one another and it's really interesting what happens when they merge.
4 points.
beautiful!
ReplyDelete