SPACE: Gaia Reveals That Most Milky Way Companion Galaxies Are Newcomers To Our Corner Of Space

dWeb.News Article from Daniel Webster dWeb.News

Science & Exploration

24/11/2021 755 views 30 likes

Data from ESA’s Gaia mission is re-writing the history of our galaxy, the Milky Way. Satellite galaxies that were once considered to be satellite galaxies of the Milky Way are now mostly new to our galactic environment.

A dwarf galaxy is a group of stars that can number between a few thousand and many billion. It has been believed for decades that the dwarf galaxies around the Milky Way are satellites. This means that they orbit our galaxy and have been our constant companions over many billions of year. Now the motions of these dwarf galaxies have been computed with unprecedented precision thanks to data from Gaia’s early third data release and the results are surprising.

Francois Hammer, Observatoire de Paris – Universite Paris Sciences et Lettres, France, and colleagues from across Europe and China, used the Gaia data to calculate the movements of 40 dwarf galaxies around the Milky Way. This was done by computing the three-dimensional velocity for each galaxy and using these to calculate its orbital energy as well as its angular (or rotational) momentum.

They found that these galaxies are moving much faster than the giant stars and star clusters that are known to be orbiting the Milky Way. They moved so fast that they couldn’t be orbiting the Milky Way yet. Interactions with the galaxy and its contents would have depleted their orbital energy, and angular momentum.

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