Study suggests that ancient gravitational force rippled through our galaxy

Preliminary data suggests that the Milky Way was hit by an ancient gravitational force that rippled through it.
By Tyler MacDonald | Apr 30, 2018
New data suggests that a strong gravitational force sent ripples through the Milky Way approximately 300 to 900 million years ago, according to Gizmodo. The findings come from the Gaia mission's data drop that happened last weekin particular, one paper that describes a potential gravitational force that could have affected our galaxy in an ancient time, like a stone thrown into a pond.

"We have here provided the clearest evidence that our own Galaxy disk has suffered from perturbations, bringing it to an out-of-equilibrium state, which may well be due to the interaction with an external satellite galaxy," reads the paper, which has yet to be peer-reviewed.

Using data on the apparent motion of 1.3 billion stars in the sky and actual velocities for over 7 million stars, the research team studied how the star velocities vary with position. The motion revealed that they are likely recovering for a gravitational force a few hundred million years ago, which is fairly recent in the universe's terms.

The gravitational force might have originated from a close approach from theSagittarius Dwarf Galaxy, which is a collection of stars that orbits the Milky Way from around 70,000 light years away..

"This work shows that the stellar disk of the Milky Way is a dynamically active place, where spiral arms and the Galactic bar leave their marks on the orbits of stars like ripples in a ponda pond that has perhaps recently felt the splash of a small stone in the form of a merging dwarf galaxy," said Stacy McGaugh from Case Western Reserve University, who wasn't involved in the study. "It is a living and breathing beast that is sensitive to be poked and prodded and even tickled a little bit."

The findings are available on preprint repository arXiv.

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