Hubble Photo Shows Two Far Off Galaxies Colliding
NGC 5256 (also known as Markarian 266) can be found by those with a powerful enough telescope in the middle of the Ursa Major "Great Bear" constellation - in this case, the powerful enough telescope just so happens to be the Hubble Space Telescope which snapped an impressive photo of the collision.
The dawn of a galactic collision. NGC 5256 is composed of two disc galaxies whose nuclei are currently just 13 000 light-years apart. https://t.co/F7kEO37PHU— HUBBLE (@HUBBLE_space) December 14, 2017
Credit: @esa / @HUBBLE_space /@NASA pic.twitter.com/Se8qBgJ1lh
In the large, plumed smattering of stars and dust, what appears to us now as a single galaxy is actually two separate galaxies in the process of crashing into each other. And while from this distance the pair seems static, in reality, they're undergoing a very tumultuous merger.
Galaxies crashing into each other aren't particularly uncommon. While space is vast and mostly empty, there are enough big collections of swirling stars that every now and then, pairs of galaxies will smash together; the Milky Way has bumped into several galaxies at different times, absorbing them into its own mass.
The two galaxies involved in the NGC 5256 merger are both disk-shaped, like our own, with a central nucleus in the form of a powerful gravity well that's likely caused by a neutron star or a supermassive black hole, around which everything else is spiraling. Here, at the respective centers of these two galaxies, is where the most violent and explosive things will occur, as the tight gravity wells will pull each other together, setting off supernovae and quasars.
Outside the very centers of these two galaxies, things are actually going to remain fairly peaceful. Because there's so much empty space in between star systems, very few of the stars within these galaxies will bump into each other, and things will, at least at first, carry on as normal, although there will eventually be some shifts in these stars' orbits as a result of the dramatic change in gravitational pulls from the two nuclei battling it out for control of the combined new galaxy.
This kind of thing is not altogether uncommon, although some mergers are brighter and more energetic than others.
For those who live in perpetual fear of some big, angry foreign galaxy coming and smashing into our own home turf, it's probably worth noting that yes, this will eventually happen - the Milky Way is on a collision course with our nearest neighbor, the Andromeda galaxy, and there's really not anything we can do about it.
The good news is that this collision won't happen for two billion years, so if any descendant of humanity does still exist by then (presumably some form of advanced chess-playing robot), the galactic merger will be their problem to deal with. Mortality has its advantages, not least the fact that we won't have to worry about the eventual possibility of the sun getting pulled into a black hole.
In the meantime, there's nothing to do but sit back and enjoy the view, as galactic events like NGC 5256 unfold. Galactic mergers may not be that rare, but they are exceptionally pretty when they do occur.