Eddie Gonzales Jr. – MessageToEagle.com – Astronomers have pieced together the cannibalistic past of our neighboring large galaxy Andromeda, which has now set its sights on the Milky Way as its next main course.
The galactic detective work found that Andromeda has eaten several smaller galaxies, likely within the last few billion years, with left-overs found in large streams of stars.
Astronomers also found traces of more small galaxies that Andromeda gobbled up even earlier, perhaps as far back as 10 billion years when it was first forming.
“The Milky Way is on a collision course with Andromeda in about four billion years. So knowing what kind of a monster our galaxy is up against is useful in finding out the Milky Way’s ultimate fate,” Dr. Dougal Mackey from the ANU Research School of Astronomy and Astrophysics, said in a press release.
“Andromeda has a much bigger and more complex stellar halo than the Milky Way, which indicates that it has cannibalized many more galaxies, possibly larger ones. The signs of ancient feasting are written in the stars orbiting Andromeda, with the team studying dense groups of stars, known as globular clusters, to reveal the ancient mealtimes.
“By tracing the faint remains of these smaller galaxies with embedded star clusters, we’ve been able to recreate the way Andromeda drew them in and ultimately enveloped them at the different times,” Dr. Mackey said.
The discovery presents several new mysteries, with the two bouts of galactic feeding coming from completely different directions.
“This is very weird and suggests that the extragalactic meals are fed from what’s known as the ‘cosmic web’ of matter that threads the universe,” said Professor Geraint Lewis from the Sydney Institute for Astronomy and University of Sydney School of Physics.
“More surprising is the discovery that the direction of the ancient feeding is the same as the bizarre ‘plane of satellites’, an unexpected alignment of dwarf galaxies orbiting Andromeda.”
Dr. Mackey and Professor Lewis were part of a team that previously discovered such planes were fragile and rapidly destroyed by Andromeda’s gravity within a few billion years.
“This deepens the mystery as the plane must be young, but it appears to be aligned with the ancient feeding of dwarf galaxies. Maybe this is because of the cosmic web, but really, this is only speculation,” Professor Lewis said.
“We’re going to have to think quite hard to unravel what this is telling us.”
Written by Eddie Gonzales Jr. – MessageToEagle.com Staff