Dark Energy Survey discovers more dwarf galaxies near the Milky Way

The Dark Energy Survey has now mapped one-eighth of the full sky (red shaded region) using the Dark Energy Camera on the Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile (foreground). This map has led to the discovery of 17 dwarf galaxy candidates in the past six months (red dots). Several of the candidates are in close proximity to the two largest dwarf galaxies orbiting the Milky Way, the Large and Small Magellanic Clouds, both of which are visible to the unaided eye.
Dark Energy Survey Collaboration

Scientists on the Dark Energy Survey, using one of the world's most powerful digital cameras, have discovered eight more faint celestial objects hovering near our Milky Way galaxy.

They believe that the objects are dwarf satellite galaxies that orbit larger galaxies.

They sometimes contain fewer than 1,000 stars, in contrast to the billions in a galaxy such as the Milky Way.

Scientists have predicted that larger galaxies are built from smaller galaxies, which are thought to be especially rich in dark matter, the substance that makes up about 25% of the total matter and energy in the Universe. Dwarf satellite galaxies, therefore, are considered key to understanding dark matter and the process by which larger galaxies form.

The main goal of the Dark Energy Survey (DES), as its name suggests, is to better understand the nature of dark energy, the mysterious stuff that makes up about 70 percent of the matter and energy in the universe. Scientists believe that dark energy is the key to understanding why the expansion of the universe is speeding up. To carry out its dark energy mission, DES takes snapshots of hundreds of millions of distant galaxies. However, some of the DES images also contain stars in dwarf galaxies much closer to the Milky Way. The same data can therefore be used to probe both dark energy, which scientists think is driving galaxies apart, and dark matter, which is thought to hold galaxies together.

"DES is finding galaxies so faint that they would have been very difficult to recognize in previous surveys," said Keith Bechtol of the University of Wisconsin-Madison.

"The discovery of so many new galaxy candidates in one-eighth of the sky could mean there are more to find around the Milky Way."

The closest of the new galaxies is about 80,000 light-years away, and the furthest about 700,000 light-years.

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