The Milky Way Ate One of Its Friends 10 Billion Years Ago

The Andromeda galaxy which researchers think will collide with the Milky Way in billions of years. One new study shows how our galaxy was shaped by a merger with a dwarf galaxy 10 billion years ago

The Andromeda galaxy which researchers think will collide with the Milky Way in billions of years. One new study shows how our galaxy was shaped by a merger with a dwarf galaxy 10 billion years ago

By looking at the chemical signatures and trajectories of the stars, Helmi's team was able to easily tell the Gaia-Enceladus stars from the "native" ones. 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.

Stars on the outskirts of our galaxy was "aliens".

This clip shows a simulation of the merger of a Milky Way-like galaxy (with its stars in blue) and a smaller galaxy (with its stars in red). She also notes that, in the future, our galaxy will merge with at least two other objects.

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

This is a characteristic of very, very old stars, since metals were only propagated throughout the Universe after the first generations of stars that forged them had died, spewing their contents into surrounding space to be incorporated into the formation of new stars.

"It has eaten many dwarf galaxies in the past, and we've just found a major one that it ate in the past". This means that when we try to look at the opposite side of the galaxy, much of our view is blocked by the stars and dust in between.But on April 25, our view of the Milky Way became much clearer. To further test that hypothesis, the team also analyzed the chemical compositions of 600 of those stars previously studied with the ground-based APOGEE stellar survey. Stars from different galaxies have their own kind of fingerprint. Another Kapteyn astronomer, Helmer Koppelman, helmed a study that spotted a "blob" of stars orbiting in the opposite direction to most of the stars in the Milky Way's halo.

"It's very cool that stars that formed in another galaxy could be lurking right next door to us", said Kim Venn, a professor at the University of Victoria's department of physics and astronomy, who was not involved in the study.

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

We are so deeply embedded in this collection that its stars surround us nearly completely, and so can be seen across most of the sky.

Helmi: That it will lead to "fireworks" in the sky. Our night sky is still being shaped by galactic collisions, and it will continue to be a shifting canvas for billions of years.

The now consumed galaxy has been given the name Gaia-Enceladus after one of the Giants in ancient Greek mythology, who was the offspring of Gaia, the Earth, and Uranus, the Sky.

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That is when our galaxy's gravity pulled a smaller companion, roughly one quarter its mass, into a risky dance: One where the dwarf galaxy plunged into and out of the Milky Way's disk, oscillating back and forth until it was finally swallowed whole.

In the latest work, researchers have traced these stars to a galaxy called Gaia-Enceladus, showing how a mega-merger between the Milky Way and the smaller galaxy helped to shape our own during its early days.

This Hubble image of the Antennae galaxies is the sharpest yet of their merger. Previous models on the Milky Way's development suggested that its halo was made from mergers with other galaxies, but no one knew the timing or the number of mergers.

But recently, the European Space Agency's Gaia spacecraft, which is taking an exquisitely detailed look at the positions and movement of more than a billion nearby stars, shook a new clue loose from the heavens.

Large galaxies get that way by absorbing lesser ones.

The research is described in a paper published today (Oct. 31) in the journal Nature. This study would not have been possible without the Gaia data.

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

Find out more in the video above.

And that galactic sleuthing is exactly what's so enticing to Helmi.

The team knew the stars had formed elsewhere, but they didn't know how they ended up floating around the Milky Way.

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