* Astronomy

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HII region RCW 120

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RE: RCW 120

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This glowing emerald nebula seen by NASA's Spitzer Space Telescope is reminiscent of the glowing ring wielded by the superhero Green Lantern. In the comic books, the diminutive Guardians of the Planet "Oa" forged his power ring, but astronomers believe rings like this are actually sculpted by the powerful light of giant "O" stars. O stars are the most massive type of star known to exist.

Credit NASA

Named RCW 120 by astronomers, this region of hot gas and glowing dust can be found in the murky clouds encircled by the tail of the constellation Scorpius. The green ring of dust is actually glowing in infrared colours that our eyes cannot see, but show up brightly when viewed by Spitzer's infrared detectors. At the center of this ring are a couple of giant stars whose intense ultraviolet light carved out the bubble, though they blend in with the other stars when viewed in infrared.

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Previously unseen star formation has been revealed in the first scientific results from the Herschel infrared space observatory.
Herschel is the largest astronomical telescope ever to be placed into space and the SPIRE instrument onboard was built by an international consortium, led by the School of Physics and Astronomy.
The new images show thousands of distant galaxies furiously building stars and one picture catches an 'impossible' star in the act of formation. The findings challenge old ideas of star birth and were presented during a major scientific symposium held at the European Space Agency (ESA), attended by leading academics from the School.
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Herschel Sees Embryo Star In RCW 120

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Herschel reveals the hidden side of star birth

The first scientific results from ESA's Herschel infrared space observatory are revealing previously hidden details of star formation. New images show thousands of distant galaxies furiously building stars and beautiful star-forming clouds draped across the Milky Way. One picture even catches an impossible star in the act of formation.
Presented today during a major scientific symposium held at the European Space Agency (ESA), the results challenge old ideas of star birth, and open new roads for future research.
Herschels observation of the star-forming cloud RCW 120 has revealed an embryonic star which looks set to turn into one of the biggest and brightest stars in our Galaxy within the next few hundred thousand years. It already contains eight to ten times the mass of the Sun and is still surrounded by an additional 2000 solar masses of gas and dust from which it can feed further.
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Herschel space telescope pierces giant star bubble

A colossal star many times the mass of our own Sun is seen growing in a bubble of gas and dust just pictured by the Herschel space observatory.
The image of the bubble, known as RCW 120, has been released a few days ahead of the European telescope's first birthday in orbit on 14 May.
Herschel's infrared detectors are tuned to see the cold materials that give birth to stars.
Pictures like RCW 120 will help explain how really giant ones are made.
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Title: Star formation around RCW 120, the perfect bubble
Authors: L. Deharveng, A. Zavagno, F. Schuller, J. Caplan, M. Pomarès, C. De Breuck

We take advantage of the very simple morphology of RCW 120 -- a perfect bubble -- to understand the mechanisms triggering star formation around an HII region and to establish what kind of stars are formed there. We present 870 microns observations of RCW 120, obtained with the APEX-LABOCA camera. These show the distribution of cold dust, and thus of neutral material. We use Spitzer-MIPS observations at 24 and 70 microns to detect the young stellar objects (YSOs) present in this region and to estimate their evolutionary stages.
A layer of dense neutral material surrounds the HII region, having been swept up during the region's expansion. This layer has a mass greater than 2000 solar masses and is fragmented, with massive fragments elongated along the ionisation front (IF). We measured the 24 microns flux of 138 sources. Of these, 39 are Class I or flat-spectrum YSOs observed in the direction of the collected layer. We show that several triggering mechanisms are acting simultaneously in the swept-up shell, where they form a second generation of stars. No massive YSOs are detected. However, a massive, compact 870 microns core lies adjacent to the IF. A 70 microns source with no 24 microns counterpart is detected at the same position. This source is a likely candidate for a Class 0 YSO. Also at 24 microns, we detect a chain of about ten regularly spaced Class I or flat spectrum sources, parallel to the IF, in the direction of the most massive fragment. We suggest that the formation of these YSOs is the result of Jeans gravitational instabilities in the collected layer. Finally, the 870 microns emission, the 24 microns emission, and the Halpha emission show the existence of an extended and partially ionised photodissociation region around RCW 120.

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