Cambridge University | 2015 Mar 10
Astronomers have discovered a ‘treasure trove’ of rare dwarf satellite galaxies orbiting our own Milky Way. The discoveries could hold the key to understanding dark matter, the mysterious substance which holds our galaxy together.
A team of astronomers from the University of Cambridge have identified nine new dwarf satellites orbiting the Milky Way, the largest number ever discovered at once. The findings, from newly-released imaging data taken from the Dark Energy Survey, may help unravel the mysteries behind dark matter, the invisible substance holding galaxies together.
The new results also mark the first discovery of dwarf galaxies – small celestial objects that orbit larger galaxies – in a decade, after dozens were found in 2005 and 2006 in the skies above the northern hemisphere. The new satellites were found in the southern hemisphere near the Large and Small Magellanic Cloud, the largest and most well-known dwarf galaxies in the Milky Way’s orbit. ...
The newly discovered objects are a billion times dimmer than the Milky Way, and a million times less massive. The closest is about 95,000 light years away, while the most distant is more than a million light years away.
According to the Cambridge team, three of the discovered objects are definite dwarf galaxies, while others could be either dwarf galaxies or globular clusters – objects with similar visible properties to dwarf galaxies, but not held together with dark matter. ...
Beasts of the Southern Wild. Discovery of a large number of Ultra Faint
satellites in the vicinity of the Magellanic Clouds - Sergey E. Koposov et al
- arXiv.org > astro-ph > arXiv:1503.02079 > 06 Mar 2015
Rare Dwarf Satellite Galaxy Candidates Found in Dark Energy Survey
DES | Fermilab | 2015 Mar 10
Scientists on two continents have independently discovered a set of celestial objects that seem to belong to the rare category of dwarf satellite galaxies orbiting our home galaxy, the Milky Way.These two images allow you to see how difficult it is to spot these dwarf galaxy candidates
in the Dark Energy Camera's images. The first image is a snapshot of DES J0335.6-5403,
a celestial object found with the Dark Energy Camera. It is the most likely of the newly
discovered candidates to be a galaxy, according to DES scientists. This object sits roughly
100,000 light-years from Earth, and contains very few stars – only about 300 could be
detected with DES data. The second image shows the detectable stars that likely belong
to this object, with all other visible matter blacked out. Dwarf satellite galaxies are so
faint that it takes an extremely sensitive instrument like the Dark Energy Camera to find
them. More analysis is required to confirm if any of the newly discovered objects are in
fact galaxies. (Credit: Fermilab/Dark Energy Survey)
Dwarf galaxies are the smallest known galaxies, and they could hold the key to understanding dark matter and the process by which larger galaxies form.
A team of researchers with the Dark Energy Survey, headquartered at the U.S. Department of Energy’s Fermi National Accelerator Laboratory, and an independent group from the University of Cambridge jointly announced their findings today. Both teams used data taken during the first year of the Dark Energy Survey, all of which is publicly available, to carry out their analysis. ...
Satellite galaxies are small celestial objects that orbit larger galaxies, such as our own Milky Way. Dwarf galaxies can be found with fewer than 100 stars and are remarkably faint and difficult to spot. (By contrast, the Milky Way, an average-sized galaxy, contains billions of stars.)
These newly discovered objects are a billion times dimmer than the Milky Way and a million times less massive. The closest of them is about 100,000 light-years away. ...
Scientists have previously found more than two dozen of these satellite galaxies around our Milky Way. About half of them were discovered in 2005 and 2006 by the Sloan Digital Sky Survey, the precursor to the Dark Energy Survey. After that initial explosion of discoveries, the rate fell to a trickle and dropped off entirely over the past five years.
The Dark Energy Survey is looking at a new portion of the southern hemisphere, covering a different area of sky than the Sloan Digital Sky Survey. The galaxies announced today were discovered in a search of only the first of the planned five years of Dark Energy Survey data, covering roughly one-third of the portion of sky that DES will study. Scientists expect that the full Dark Energy Survey will find up to 30 of these satellite galaxies within its area of study. ...
Eight New Milky Way Companions Discovered in First-Year Dark Energy Survey Data - DES Collaboration
- arXiv.org > astro-ph > arXiv:1503.02584 > 09 Mar 2015