The gravitational waltz of the Milky Way’s satellites

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I’ve started contributing to the Forbes Science page again! This is my first new contribution, relating to the second data release from the Gaia survey telescope. (And if I can be shameless: Forbes pays according to traffic, so the more of you who share and visit and read my stuff, the better they pay me. Ahem.)

Plotting The Three-Dimensional Dance Of Galaxies

A map of the Milky Way’s satellite galaxies, globular clusters, and other objects in orbit. [Credit: ESA/Gaia]

For Forbes:

The European Space Agency’s Gaia telescope is designed to map the position and speed of a billion stars in the Milky Way and its neighboring galaxies. In fact, some of those galaxies are satellites, which whirl around our home galaxy in a complicated dance. Part of Gaia’s mission is to help us understand that dance.

Many of these satellite galaxies actually orbit inside the halo of the mysterious, invisible dark matter that makes up most of the Milky Way’s mass. For that reason, the dance of the satellites tells us about the structure of the Milky Way, along with the shared history and evolution of all the galaxies involved. The Gaia space telescope’s second data release from last week allowed astronomers to map out the positions and motion of stars inside eleven satellite galaxies, along with other star clusters. The result: new estimate on the mass of the Milky Way, and a fully three-dimensional map of nearly 90 objects in orbit around our galaxy.

[Read the rest at Forbes]