A Puzzle a la Herschel

NGC 7538 from Herschel. Image credit: ESA/NASA/JPL-Caltech/Whitman College

NGC 7538 from Herschel. Image credit: ESA/NASA/JPL-Caltech/Whitman College

We know that NGC 7538 is a star factory from Herschel data (see earlier post), turns out there is a puzzling feature located there too:

The Herschel Space Observatory has uncovered a weird ring of dusty material while obtaining one of the sharpest scans to date of a huge cloud of gas and dust, called NGC 7538. The gigantic ring structure is situated at the center-top of this image. The odd ovoid possesses the mass of 500 suns, with its long axis spanning about 35 light-years and its short axis about 25 light-years.
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