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Enormous Dwarf Galaxy Found Orbiting the Milky Way

November 28, 2018
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Enormous Dwarf Galaxy Found Orbiting the Milky Way

Astronomers have just discovered a new satellite dwarf galaxy orbiting the Milky Way. It lies in the constellation Antlia.

So, researchers named the new satellite Antlia 2 or Ant 2. It is as big as the LMC (Large Magellanic Cloud), or about one-third of the size of the Milky Way. However, Ant 2 is amazingly faint – around 4000 times fainter than the LMC.

Astronomers discovered the new object searching through data from ESA’s Gaia spacecraft.

Dozens of smaller, gravitationally bound galaxies orbit the Milky Way. So, the discovery team says they might find many more similar-type galaxies soon.

Researchers detailed their finding in a paper published November 9 on arXiv.org.

Astronomers describe Ant 2 to have the lowest known surface brightness of any system by far. It is approximately 100 times more diffuse than the so-called ultra diffuse galaxies (UDGs) that populate the Universe.

The Discovery

With the aim of finding more satellites orbiting our galaxy, a team of astronomers led by Gabriel Torrealba of Academia Sinica in Taipei, Taiwan, has conducted a search for new satellites, especially dwarf galaxies. Thus, discovering the existence of Antlia 2. For their study, the researchers used a combination of astrometry, photometry and variability data provided by Gaia Data Release 2 (DR2).

However, to confirm the nature of Ant 2, scientists used spectroscopic observations with the 2dF+AAOmega Spectrograph on the 3.9 m Anglo-Australian Telescope and archival DECam imaging.

“In this paper, we use Gaia Data Release 2 (GDR2, Gaia Collaboration et al. 2018b) to discover and analyze a new dwarf satellite galaxy orbiting the Milky Way. The discovery was made at the Flatiron Gaia Sprint 2018,” the researchers wrote in the paper.

Antlia 2 is the most diffuse galaxy ever found. Therefore, it could be just the remains of a galaxy long dead.

The satellite galaxy lies some 424,000 light years away from the Earth and is estimated to be about 11.2 billion years old.

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Thumbnail image: Antlia 2 (top left), hidden on the other side of the Milky Way, is the size of the Great Magellanic Cloud (bottom right), but much weaker. (Artists added a bright, artificial spot representing Antlia 2 to show its position.) Credit: G. Torrealba, Academia Sinica, Taiwan; V. Belokurov, Cambridge, U.K., and CCA, New York, USA, based on a picture of ESO / S. Brunie

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