How A Catastrophic Cosmic Collision Changed the Milky Way Forever

Mindy Sparks
November 2, 2018

Based on these data, scientists have calculated that the boundaries of the milky Way is expanding to 15 billion kilometers per year. For example, researchers always been a question about how it was formed halos - large-scale structure of stars, dark matter and gas that surrounds the galactic disk. They think that a dwarf galaxy with about a fourth the mass of the Milky Way was pulled inside our home galaxy and then torn apart by our greater gravitational force, its constituent stars spread out and integrated into their new home.

Some stars have been measured more than 70 times as the satellite ― circling the Sun as it orbits Earth ― continuously scans the galaxy.

As UNIAN reported earlier, new research has shown that the milky Way for the second extends approximately 500 meters due to the formation of new stars on the outskirts.

She also added that it's a tremendously exciting result, because now we know something new and deeply significant about our home galaxy.

Before this discovery, the team had run simulations of galactic mergers.

Although Gaia-Enceladus is expected to have been about ten times smaller than the current Milky Way, it was still large; large enough to have collections of stars called globular clusters trailing after it. "This is like a police investigation - this one in particular, because it's not a galaxy that we can see today". The collision scrambled the orbits of stars in its disk, making it much puffier, and sent alien stars flying all around the Milky Way, thus building much of its halo.

"We became only certain about our interpretation after complementing the Gaia data with additional information about the chemical composition of stars, supplied by the ground-based APOGEE survey", says Carine Babusiaux, Université Grenoble Alpes, France, and second author of the paper. "It's a dead galaxy, so that makes it kind of fun". The chemical signature of many halo stars was clearly different from the "native" Milky Way stars. "At almost three million light-years away, we're never going to Andromeda to populate it or study it in detail", says Kim Venn, an astronomer at the University of Victoria in British Columbia who was not involved in the study.


The merger would have produced brilliant stellar explosions - supernovas - and the rapid birth of stars.

"If you were there ... you would see bright, blue young stars". One of these mergers will be with the Andromeda galaxy, in at least 5 billion years, Helmi said. Our night sky is still being shaped by galactic collisions, and it will continue to be a shifting canvas for billions of years.

The team named the deceased galaxy "Gaia-Enceladus", in honor of the space observatory and a being from Greek mythology, Enceladus, a giant who was believed to be buried under the Mount Etna volcano and responsible for the earthquakes in the region. In addition, the stars from the smaller galaxy that fell into the Milky Way 10 billion years ago still form a population of stars that are rotating around the Milky Way center, in a sense contrary to the majority of the stars.

But 10 billion years ago, the Milky Way was itself much smaller, which illustrates the explosive, star-creating power of the merger.

This Hubble image of the Antennae galaxies is the sharpest yet of their merger.

The researchers hope that by understanding the collision in the Milky Way, they can better understand the process in other galaxies as well. "It was fantastic to look at the new Gaia data and realize that I had seen it before!" said the astronomer. "By studying these stars that were present in these galaxies, you get a way of understanding the properties of galaxies".

"What I really like is that Gaia data was combined with the ..."

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