The galaxies NGC 4490 and NGC 4485 are caught in a lovers' embrace, a cosmic tryst that is all the more romantic because NGC 4490 apparently just got over a bad relationship, cannibalistically eating its previous lover.
Hmmm, maybe I pushed that anthropomorphized analogy a bit far. But the essence of it is correct: While these galaxies are in the process of colliding, one of them apparently already collided and merged with a galaxy a billion or three years ago!
The evidence comes from somewhat disparate observations of NGC 4490, the larger of the two galaxies, showing it has two nuclei. Usually, galaxies have a single nucleus, the central concentrated volume of stars in their cores. But a new paper by a team of astronomers show that NGC 4490 has two, and the most likely explanation is that we're seeing the late stages of a galactic merger*.
The pair of galaxies NGC 4485 (top) and NGC 4490 (bottom) are interacting, causing their shapes to distort and triggering huge amounts of star formation. Credit: SDSS/ALADIN
First though, the story behind the observations is pretty great. Allen Lawrence is a 77-year-old amateur astronomer who wanted to do some professional-level research. He ...