It sounds like a crime committed in a Greek candy shop, but it’s actually more like a horror movie created by astronomers. According to a new study, the Andromeda galaxy was once and possibly still is a cannibalistic star conglomeration that consumed a sibling of the Milky Way and some of its own smaller siblings … and could one day eat the Milky Way too. If there’s no sound in space, what’s that chomping, slurping and burping noise?
The terrifying report, published in Nature Astronomy, comes from University of Michigan astronomers Richard D’Souza and Eric Bell. They were studying the Local Group – the collection of at least 54 galaxies that lists the Milky Way and Andromeda as its largest and has its gravitational center right between the two of them. It’s predicted that the Local Group will someday – possibly 4 billion years from now – become the Local One as all of the members collapse into the center.
Collapse? Or should we say ‘are consumed by one giant cannibalistic galaxy that is probably Andromeda’?
That may be what the models developed by D’Souza and Bell are suggesting when they used them to analyze the faint halo of stars surrounding Andromeda. Once thought to be the crumbs of many small galaxies eaten by Andromeda, the simulations instead showed that the stars were potentially from a single large galaxy surpassed in size only by Andromeda and the Milky Way. Furthermore, that giant galaxy was most likely a fraternal twin of the Milky Way that astronomers never knew existed. The astronomers named it M32p after the M32 halo around Andromeda that’s the faint reminder of what it once was … and a faint predictor of what may happen to its surviving sibling.
But first, Andromeda would probably turn the Milky Way into a form of the mysterious M32 – a small, dense satellite galaxy made of both old and new stars that has long puzzled astronomers like Bell … until now.
“M32 is a weirdo. While it looks like a compact example of an old, elliptical galaxy, it actually has lots of young stars. It’s one of the most compact galaxies in the universe. There isn’t another galaxy like it.”
The model shows that this “weirdo” is actually the remaining center of Milky Way sibling M32p, likened to the nearly indestructible pit of a galactic peach sloppily chomped to near extinction by a cannibalistic celestial companion. While the pit remains whole, the rest of the M32 peach is now part of Andromeda’s huge galactic disc, which the simulation shows is sturdy enough to have survived many galactic collisions.
Will the Disc of Andromeda (a great name for a band) be all that’s left in four billion years when the Large Group becomes one? Will there be anyone left to sing along?