Video: Milky Way’s Warp Caused by Collision Between Galaxies - ESA

Using data from the European Space Agency’s (ESA) star-mapping satellite Gaia, scientists have been able to determine that the Milky Way is warping at a speed much faster than anticipated - suggesting our galaxy may be colliding with another star system.

While scientists have come to a consensus on the fact that the Milky Way’s disc is warped, the ESA revealed Thursday that astronomers may have finally discovered exactly why this process is occurring in our galaxy.

While initial theories surrounding the galaxy’s mysterious warp pointed to the possibility of it being static, the data from Gaia Data Release 2 proved not only that it was ongoing, but also exceeding expectations for its presumed velocity.

“We measured the speed of the warp by comparing the data with our models. Based on the obtained velocity, the warp would complete one rotation around the center of the Milky Way in 600 to 700 million years,” said lead researcher Eloisa Poggio of the Turin Astrophysical Observatory.

This unexpected velocity leads researchers to believe that the Milky Way is clashing with a dwarf galaxy.

“That’s much faster than what we expected based on predictions from other models, such as those looking at the effects of the non-spherical halo,” she added.

Thanks to data from the ESA’s star mapping satellite, the researchers were able to determine the distances from Earth of over 1 billion stars and track their journeys over millions of years.

“It’s like having a car and trying to measure the velocity and direction of travel of this car over a very short period of time and then, based on those values, trying to model the past and future trajectory of the car,” said co-author Ronald Drimmel, a research astronomer at the Turin Astrophysical Observatory.

“If we make such measurements for many cars, we could model the flow of traffic. Similarly, by measuring the apparent motions of millions of stars across the sky we can model large scale processes such as the motion of the warp.”

The structure of our galaxy, the Milky Way, with its warped galactic disc, where the majority of its hundreds of billions of stars reside. Data from ESA's star-observer Gaia recently proved that the disc's warp is precessing, essentially moving around similarly to a wobbling spinning top. The speed of the warp's rotation is so high that it must have been caused by a rather powerful event, astronomers believe, perhaps an ongoing collision with another, smaller, galaxy which sends ripples through the disc like a rock thrown into water.

© European Space Agency

Though the astronomers have yet to determine which galaxy is causing these ripples through the Milky Way, the ESA release noted that one possible star system could be the dwarf galaxy Sagittarius, which scientists believe has already passed through our galaxy several times before.