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Captain, dark energy sensor readings show dwarf galaxies orbiting the Milky Way

Looks like our galaxy might be getting a little bigger, Mr Spock

By Iain Thomson, 18 Aug 2015

Astronomy teams at the University of Cambridge and America's Fermilab looking for evidence of dark matter have spotted eight (relatively) tiny galaxies orbiting our Milky Way.

"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."

Dwarf galaxies certainly live up to their name – they can contain only a few hundred stars (the smallest dwarf found had just 500) compared to the billions of stars in the Milky Way, which is an average-sized galaxy. The eight dwarfs are orbiting up at a distance of between 80,000 and 700,000 light years, but may eventually merge with the Milky Way and add to its mass.

The galaxies were discovered using the Dark Energy camera (DECam), which at 570 megapixels is the most advanced and expensive digital camera ever built. Installed at the Victor M. Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile, the DECam was examining a section of the southern skies and was able to pick up the tiny, faint galaxies.

The Dark Energy Survey (DES) is part of an ongoing scientific quest to understand the mysteries of dark energy, which accounts for around 75 per cent of the universe. The survey maps out galaxies and is trying to understand how they have expanded over time.

The theory stems from the 1998 Nobel Prize-winning discovery that the universe's expansion is speeding up. Einstein's theory of General Relativity suggests that gravity should slow the expansion of the universe, but dark energy could provide an opposite force to gravity that keeps things moving outward rapidly.

"This exciting discovery is the product of a strong collaborative effort from the entire DES team," said Basilio Santiago, a DES Milky Way Science Working Group coordinator and a member of the DES-Brazil Consortium. "We've only just begun our probe of the cosmos, and we're looking forward to more exciting discoveries in the coming years." ®

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