3D map of the Milky Way shows its twisted warped shape is changing — and it could be because of an ongoing collision

• New data collected by the European Space Agency’s (ESA) Gaia satellite shows that not only is the Milky Way warped, but its shape is shifting.
  
• The speed of the change indicates that the Milky Way’s twisted and warped shape may be the result of an ongoing collision.
  
• Astronomers do not know which galaxy is colliding with the Milky Way, however, Sagittarius is a likely candidate.
  

Just like the Earth was once thought to be flat, so was the Milky Way. However, a new 3D map of the galaxy shows otherwise. While being spiral in shape, the galaxy’s disk is a warped and twisted shape.

New data from the European Space Agency’s ($4) Gaia satellite now shows that the even that warped shape isn’t static — it’s on the move. The constant change should mean that the Milky Way in the midst of a collision with another galaxy, especially because the data shows that the Milky Way is changing shape much faster than expected.


Astronomers have dubbed this phenomenon as "precession” comparing it to the wobble of a spinning top as it rotates. "Based on the obtained velocity, the warp would complete one rotation around the centre of the Milky Way in 600 to 700 million years,” said the lead author of the study published in $4, $4.

The most likely candidate
While astronomers believe that the most likely reason for the $4 changing shape in an ongoing collision with another galaxy, they have no idea which one. The most likely candidate is Sagittarius, a dwarf galaxy that is in orbit around the Milky Way.

Previous studies indicate that Sagittarius, being the smaller galaxy, will eventually be absorbed by the Milky Way. A process that many believe is already underway.

The Milky Way is no stranger to cannibalism. A study published in January found evidence of the galaxy having gobbled up $4, a dwarf galaxy, between 11.6 to 13.2 billion years ago.


Even though the Milky Way might be in the middle of a merger, it’s no cause to panic. While an ongoing collision is an impressive feat on the galactic scale, it’s unlikely to have any impact on life on Earth. "The Sun is at a distance of 26,000 light-years from the galactic centre where the amplitude of the warp is very small,” said Poggio.

A better understanding of the Milky Way’s shape can help astronomers understand how it evolved over time.

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