The general perception about our Milky Way galaxy is that it resembles a flat disc full of billions of stars including our Sun. But as things usually go in astronomy, surprises also occur in this case.
Phys.org writes that the Milky Way’s ‘disc’ is warped rather than being symmetrical, and the warped edges are also constantly moving around the outer rim of our galaxy.
Milky Way resembles the waves from a stadium
Xinlun Cheng, who’s an astronomy graduate student from the University of Virginia’s College and Graduate School of Arts & Sciences, explained:
If you have ever seen the audience making a wave in a stadium, it’s very similar to that concept,
He also added:
Each member of the audience stands up and then sits down at the correct time and in the correct order to create the wave as it goes around the stadium. That’s exactly what stars in our galaxy are doing. Only in this case, as the wave is going around the galaxy’s disk, the galaxy disk is also rotating around the center of the galaxy. In terms of the sports-fan analogy, it’s as if the stadium itself is also rotating.
What could have caused the warp to occur is a subject of debate among scientists. Some of them are betting on the idea that a collision between our galaxy and another from the distant past was the culprit.
Collision with the Sagittarius Dwarf Spheroidal Galaxy?
In a new study made after gathering data from the Gaia observatory and the infrared spectograph APOGEE, scientists concluded that the warp is not a result of the Milky Way’s own internal mass. Instead, they’re betting on the relic of gravitational tugging on our galaxy’s disk by the close approach of a satellite galaxy. The Sagittarius Dwarf Spheroidal Galaxy could have been the other group of stars involved, and the hypothetical collision happened around 3 billion years ago.
The article, “Exploring the Galactic Warp through Asymmetries in the Kinematics of the Galactic Disk,” of Cheng and his colleagues, was published in The Astrophysical Journal.