The Milky Way is Still Rippling from a Galactic Collision Millions of Years Ago

Universe Today | 9/24/2018 | Staff
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Between 300 million and 900 million years ago, our Milky Way galaxy nearly collided with the Sagittarius dwarf galaxy. Data from the ESA’s Gaia mission shows the ongoing effect of this event, with stars moving like ripples on the surface of a pond. The galactic collision is part of an ongoing cannibalization of the dwarf galaxy by the much-larger Milky Way.

“At the beginning the features were very weird to us.” – Teresa Antoja, Lead Researcher, Universität de Barcelona, Spain.

Gaia - Science - Objective - Survey - Stars

Gaia’s main science objective is to survey one billion stars in our galactic neighborhood. It’s creating a precision 3D map of the Milky Way, and answering questions about the origin and evolution of our galaxy. The ESA launched Gaia in 2013 on a planned five-year mission.

Gaia discovered the encounter between the Milky Way and the Sagittarius dwarf galaxy by mapping the movement of stars in the Milky Way’s galactic disc. Gaia accurately measures the positions and precise velocities of a billion stars. The spacecraft worked out what’s known as ‘phase space’ for a subset of a few million stars, by estimating the three-dimensional velocities for those stars. This phase space, or combination of position and velocity, allowed scientists to study the stellar motion of stars in the disc.

ESA - Gaia - Mission - Mission - Stars

The ESA’s Gaia mission is currently on a five-year mission to map the stars of the Milky Way. Gaia has found evidence for a galactic collision that occurred between 300 million and 900 million years ago. Image credit: ESA/ATG medialab; background: ESO/S. Brunier.

“I was a bit shocked and I thought there could be a problem with the data because the shapes are so clear.” – Teresa Antoja, Universitat de Barcelona, Spain.

Motions - Phase - Space - Something - Shocking

The stellar motions in phase space revealed something shocking and unexpected. Lead researcher Teresa Antoja, from the Universität de Barcelona in Spain, was shocked by...
(Excerpt) Read more at: Universe Today
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