Merging Galaxies

There are billions of galaxies in the Universe, and the Universe is a large place.  However, if our own galaxy is anything to go by, galactic collisions still frequent the cosmos.  While our galaxy has collided with at least three dwarf galaxies in its past, major collisions between full-size galaxies are a spectacle to behold.  Two such galaxies were recently studied by NASA’s NuSTAR X-ray telescope.  In the observations, the supermassive black holes of each galaxy were swallowing more and more matter, some from their galaxy and some from the other galaxy.  In fact the only way NASA was able to tell the black holes were active was because of intense X-rays (thus the requirement of NuSTAR’s observation); there was so much dust and gas surrounding these black holes, whatever other light that might be visible is blocked out.  In fact, this shell of debris is so thick, its only high-end X-rays that are visible to NuSTAR.

Galaxies have long and tumultuous histories; supernovae that outshine it for brief seconds, minor collisions, major collisions, and suffering the wrath of a neighboring quasar.  Collisions are just another part in a galaxy’s life, and thanks to the coalescing gases at the centers of these two galaxies, new stars may form from ejected materiel.  At the end of this collision (and any/every other collision) a new kind of galaxy will emerge; stars from both galaxies, gases, dust.  This too will lead to the birth of stars with unique compositions, unique planets will also form.


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