A team of astronomers has managed, in true Sherlock Holmes style, to reconstruct the cannibalistic past of Andromeda, our neighboring galaxy, which will cannibalize the Milky Way in 4,000 million years. The galactic agape of our voracious companion has been published in the journal Nature.
Scientists discovered that Andromeda – which is 2.537 million light-years distant from Earth – has already eaten several galaxies smaller than it, probably in the last billions of years, as they have found remains in large streams of stars.
Andromeda will devour us in 4 billion years
Australian National University researcher Dougal Mackey , who co-led the study with Professor Geraint Lewis of the University of Sydney, both in Australia, commented that the international research team found very faint traces of galaxies smaller than Andromeda engulfed even earlier, perhaps up to 10,000 million years earlier, at the time of its formation.
“The Milky Way is on a collision course with Andromeda in about four billion years. Therefore, knowing what kind of monster our galaxy is facing is useful in discovering the final destination of the Milky Way, ” said Mackey. “Andromeda has a much larger and more complex stellar halo than the Milky Way, indicating that it has cannibalized many more, possibly larger, galaxies.”
Cosmic banquet
The signs of this ancient feast are written in the stars orbiting the Andromeda galaxy, and the team studied dense clusters of stars, known as globular clusters, to reveal the details of this cosmic feast.
“By tracking the faint remnants of these tiny galaxies embedded in star clusters, we have been able to recreate the way Andromeda attracted and ultimately engulfed them at different times,” Mackey said.
This discovery presents , how could it be otherwise (we still have much to discover) several new mysteries, with the two galactic feeding episodes discovered coming from completely different directions.
“This is very strange and suggests that extragalactic foods feed on what is known as the ‘cosmic web’ of matter that threads the universe, ” said Lewis, a co-author of the work.
“We will have to think hard to figure out what this is telling us,” experts say.
Mackey also said that studying Andromeda offered new data about the way our galaxy has grown and evolved over billions of years.
“ One of our main motivations when studying astronomy is to understand our place in the universe . One way to learn about our galaxy is to study others that are similar to it and try to understand how these systems formed and evolved. Sometimes this can be more easier than looking at the Milky Way, because we live inside it and that can make certain types of observations difficult, “comment the astronomers.
Cosmic archeology
The research analyzed data from the Archaeological Survey of Pan-Andromeda, known as PANDAS q ue has institutions in Australia, New Zealand, the United Kingdom, the Netherlands, Canada, France and Germany, and uses the telescope Hawaii Canada-France, Gemini North telescope, Keck telescope, NOAO Mayall 4m telescope and William Herschel telescope.
“We are cosmic archaeologists, except that we are digging through the fossils of long-dead galaxies rather than human history,” said Lewis, who is a prominent member of that survey.
Referencia: Dougal Mackey, Geraint F. Lewis, Brendon J. Brewer, Annette M. N. Ferguson, Jovan Veljanoski, Avon P. Huxor, Michelle L. M. Collins, Patrick Côté, Rodrigo A. Ibata, Mike J. Irwin, Nicolas Martin, Alan W. McConnachie, Jorge Peñarrubia, Nial Tanvir & Zhen Wan. Two major accretion epochs in M31 from two distinct populations of globular clusters. Nature, 2019 DOI: 10.1038/s41586-019-1597-1
