An artist’s impression of the Andromeda galaxy.

Sebastian Zentimolo

The galaxy subsequent door to our warped and twisted Milky Manner is, formally, a monster. Astronomers learning the Andromeda galaxy have found the large spiral galaxy has fairly the cannibalistic previous. On two separate events during the last 10 billion years, Andromeda has devoured up smaller galaxies however the best way wherein it devoured them has astronomers puzzled. 

“We have recognized for about 10 to 15 years that Andromeda has had a way more violent previous, by way of swallowing smaller galaxies, than the Milky Manner has,” says Dougal Mackey, a researcher at Australian Nationwide College and first creator on the brand new research.

The analysis, carried out by Mackey and a world crew of collaborators, was revealed within the journal Nature on Oct. 2 and reconstructs the historical past of the Andromeda galaxy in higher element than ever earlier than. After analyzing 77 globular clusters — dense knots of round one million stars every — orbiting Andromeda and measuring their velocities, the crew stumbled upon one thing fairly shocking. 

One of the best clarification for his or her information suggests Andromeda cannibalized a galaxy (or a number of galaxies) at the least twice during the last 10 billion years. One in every of these feeding frenzies occurred lately, however the different is far more historical. Somewhat than progressively absorbing stars and clusters over time, Andromeda has been “binge-eating in distinct periods,” based on Geraint Lewis, an astronomer with Sydney College and co-author on the research. 

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It will get a bit weirder, although. The way in which that Andromeda’s two binge periods occurred has intrigued the researchers as a result of it seems the galaxy’s meals got here from two completely different instructions. The older clusters are spinning round Andromeda in the same technique to how rings spin round Saturn. However the different cluster strikes round Andromeda perpendicular to the growing older cluster. 

“If that’s the case, then there seem like particular instructions from which galaxies “choose” to reach,” says Mackey. 

That phenomenon may level to a galaxy formation position for the community of filaments and voids forming the premise of our Universe, the so-called “cosmic net.”

The net is “a sponge-like distribution of matter, with dense knots and empty voids, and filaments and sheets in between,” says Lewis. You would possibly have a look at the universe and suppose all the celebrities have been simply randomly dropped into place, as if an almighty god simply scattered its marbles, however the cosmic net exhibits how the universe is richly linked. The speculation then, is that this net helped feed Andromeda its meals and that is why we see clusters rotating round it at 90 levels. 

“We all know that matter flows out of voids and alongside the filaments and into galaxies, which could recommend that Andromeda has been getting meals from outlined instructions from the cosmic net.”

Lewis says the crew aren’t fairly certain that speculation holds true however it’s an intriguing notion.

The crew will now analyze the globular clusters used within the analysis in higher element, hoping to drag aside the newest Andromeda feed and decide precisely what it ate. Was it one galaxy? Two? Many small dwarf galaxies? That is what they hope to search out out.

Mackey additionally says they hope to “weigh” Andromeda.

“In the meanwhile we’re not even sure whether or not the Milky Manner or Andromeda is the extra large system.” he says. “It is very tough to precisely weigh galaxies … however the clusters would possibly give us a means ahead right here.”

The monster residing subsequent door is ultimately going to swallow up our house galaxy, too.

After all, there is no must panic. The Milky Manner’s demise by galactic cannibalism is slated to happen some 4 billion years from now. Hopefully, astronomers will come to some conclusions about Andromeda’s cannibalistic tendencies and its weight earlier than then.