An analysis of the Pan-Andromeda Archaeological Survey (PANDAS) revealed two major episodes of buildup, probably separated by the billions of years in which the Andromeda Galaxy, a neighbor of our Milky Way Galaxy, twisted several small galaxies.
Large galaxies, similar to the one we live in, are thought to be growing due to repeated mergers with dwarf galaxies.
Gas and dwarf galaxies in a vast cosmic web follow gravitational paths lined by dark filaments, slowly moving to collections of dark matter and gathering into large galaxies.
When dwarf galaxies are drawn by gravity, they also detach from each other, leaving behind long drawn streams of stars and compact star clusters.
The Australian Astronomer at National University Dougal McKee and his colleagues found evidence of two major migratory events in the history of Andromeda: a more recent migration event occurred several billion years ago, and an older event about 10 billion years ago.
The evidence comes from "galactic" archeology, "the use of the motions and properties of stars and stellar clusters to reconstruct the formation and evolutionary history of galaxies.
" The Milky Way and We Are Coming to an Andromeda Collision in About 4 Billion Years – Dr. Ma said .
"Therefore, knowing which monster our Galaxy is resisting is useful for figuring out the ultimate fate of the Milky Way."
Doctor. Mackay and co-authors analyzed the movements and properties of 77 globular clusters and several large stellar structures in the Andromeda halo. This allowed them to reproduce how the galaxy painted smaller galaxies.
"By tracking the faint remnants of these smaller galaxies with built-in star clusters, we were able to reproduce how Andromeda drew them in, and ultimately wrapped them in" 19269005] "To see two different meal times for Andromeda was quite amazing," she said Surrey University astronomer Michelle Collins.
"The path of globular clusters around Andromeda suggests that this galaxy had breakfast about 10 billion years ago, and a big dinner, perhaps only a few billion years ago. "
The discovery presents several new secrets, with two bouts of galactic power coming from completely different directions.
There are strikingly different directions, as two populations of globular clusters orbit at right angles to each other, "said Dr. Collins.
" This orientation can tell us something about the spider web embedded by Andromeda and the Milky Way.
"This is very strange, and it says that extragalactic foods are fed by what is known as the cosmic web of matter that inflates the universe," said Professor Heroin Lewis of the University of Sydney Institute of Astronomy Sydney.
"B. More surprising is the discovery that the direction of ancient feeding is the same as the bizarre "plane of the satellites," the unexpected alignment of dwarf galaxies orbiting around Andromeda.
The results were published in the October 3, 2019 issue of Nature . .
Dugal McKee and others 2019. Two major ecoregion epochs in the M31 of two different populations of globular clusters. Nature 574: 69-71; doi: 10.1038 / s41586-019-1597-1