Astronomers Accidentally Discover a Hidden Galaxy Right Next Door

Mindy Sparks
February 3, 2019

During relatively recent work on imaging NGC 6752, a globular star cluster located around 13,000 light-years from the Milky Way's halo, Hubble made a surprise discovery: a previously unknown dwarf galaxy. The Hubble Space Telescope team initially planned to determine the age of a globular cluster by measuring its faintest stars, but ended up stumbling upon a small galaxy while doing so.

The researchers determined that this galaxy - nicknamed Bedin 1, after discovery team leader L. R. Bedin of the INAF-Osservatorio Astronomico di Padova in Italy - is a "spheroidal dwarf" just 3,000 light-years wide.

But Bedin 1 stands out from the crowd.

Dwarf galaxies are common in the universe, but most ride the coattails of larger galaxies. But that's how it goes sometimes, and the authors of the new study, published this week in the Monthly Notices of the Royal Astronomical Society, couldn't be happier. After a careful analysis of their brightnesses and temperatures, the astronomers concluded that these stars did not belong to the cluster - which is part of the Milky Way - but rather they are millions of light-years more distant. NASA has shared a stunning image of the dwarf galaxy that was captured by Hubble.

This "loner galaxy" is about 30 million light years away, or 2,300 times farther away than the clusters in the foreground of the image. 36 galaxies of this type are already known to exist in the Local Group of Galaxies, 22 of which are satellite galaxies of the Milky Way.

Dwarf spheroidal galaxies are defined by their small size, low-luminosity, lack of dust and old stellar populations [1].

Almost all the stars astronomers measured in Bedin 1 are small and old, implying the dwarf galaxy made all its stars in a single burst of activity some 10 billion years ago.

"This makes it possible the most isolated small dwarf galaxy discovered to date".

Not only is this dwarf galaxy old, it's also remarkably isolated and undisturbed.

"The discovery of Bedin 1 was a truly serendipitous find", the ESA said.

"Very few Hubble images allow such faint objects to be seen, and they cover only a small area of the sky", said the European Space Agency. As telescopes on the ground and in space become more sophisticated, it seems highly likely that it's only a matter of time before more nearby cosmic fossils are dug up. Second, Bedin 1 shows little sign of past interactions with any galactic neighbors.

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