The Milky Way gobbled up another galaxy 11.5 billion years ago — and it could provide clues to why the galaxy is twisted up in a spiral shape

• Scientists always knew that the Milky Way, in its early days, ate up another galaxy.
  
• A new study published in Nature has been able to pinpoint exactly when the collision occurred.
  
• By studying a star, scientists were able to determine that, our home galaxy gobbled up a dwarf galaxy, Gaia Enceladus, between 11.6 to 13.2 billion years ago.
  

Just like Hungry Hungry Hippos gobbles up anything that gets in its way, the Milky Way gobbled up another galaxy in its early days — Gaia Enceladus. When this discovery was made last year, the scientists only knew that whatever had happened, happened over 10 billion years ago.

In order to know exactly how it may have affected our galaxy, they needed an exact date. It could even be a piece in the age-old puzzle of scientists trying to figure out how the Milky Way got its warped and twisty shape. And, now they have one.

By studying the star, v Indi, a team of researchers were able to pinpoint when the collision occurred. The study published in Nature suggests that v Indi was already a part of the Milky Way before the collision.

Therefore, the star’s age and mass measurements indicate that galactic cannibalism happened somewhere between 11.6 to 13.2 billion years ago.

Using a star to find explosions in the past
Using asteroseismology — the study of how stars in the universe glow and ebb — researchers were able to determine that the star, v Indi was approximately 11 billion years old. Therefore, from the early days of the Milky Way.

"Similar to the way seismic waves on Earth allow conclusions about the interior of our planet, stellar oscillations help us to reveal the internal structure and composition of the star and thus its age," explains Nathalie Themessl, co-author of the study.

In addition, the Transiting Exoplanet Survey Satellite (TESS) indicated that v Indi is located in the region of space where the Milky Way ate up Gaia-Enceladus.

"Since the motion of ν Indi was affected by the Gaia-Enceladus collision, the collision must have happened once the star had formed," said Bill Chaplin, lead author of the study published in Nature.

Milky Way’s neighbour, the Andromeda galaxy, is another collision waiting to happen. According to NASA, both galaxies will collide at a speed of 402,336 kph, 3.75 billion years down the line. Earth will survive — but its skies will be changed forever.

See also:
New stars running from the death of their own galaxies means our Milky Way might survive

Bubbles filled with thousands of stars found in the Milky Way

Milky Way's neighbour might not be so ‘dead’ with young stars brewing at its center