In DepthAstronomy

Large galaxy found lurking on the Milky Way's far side

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Science  16 Nov 2018:
Vol. 362, Issue 6416, pp. 737
DOI: 10.1126/science.362.6416.737

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Summary

Circling our galaxy is a stealthy giant. Astronomers have discovered a dwarf galaxy, called Antlia 2, that is one-third the size of the Milky Way itself. As big as the Large Magellanic Cloud, the galaxy's largest companion, Antlia 2 eluded detection until now because it is 10,000 times fainter. Such a strange beast challenges models of galaxy formation and dark matter, the unseen stuff that helps pull galaxies together. The galaxy was discovered with data from the European Space Agency's Gaia satellite, a space telescope measuring the motions and properties of 1 billion stars in and around the Milky Way.