ngc 7538

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NGC 7538 by Remidone
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Camera: SBIG ST-10XME sensor -20°C with Sbig CFW10 and SXV-AO-LF Optics: GSO 10" f/8 RC carbon fiber Filters: Baader Exposure time (seconds): HA: 39×1200 bin 1×1 SII: 17×1200 bin 1×1 OIII: 19×1200 bin 1×1 Place: Pesaro (PU) Italy Date: 27/08/2016 - 02/09/2016

NGC 7635 (Bubble Nebula), Sh2-159, NGC 7538
Credit: Emil Ivanov

The Bubble Nebula (NGC 7635, Sharpless 162, or Caldwell 11), is an emission nebula in the constellation Cassiopeia. The “bubble” is created by the stellar wind from a massive central star,SAO 20575 (estimated mass 10-40 Solar masses). The adjacent giant molecular cloud contains the expansion of the bubble nebula while itself being excited by the hot central star, causing it to glow. Below the Bubble Nebula is the emission nebula Sharpless 159. This H II region, contains within it a very compact source of radio waves, which coincides with the densest part of the cloud, and surrounds a star of spectral type O9, which is the main source of ionization of gases in the region. At the upper left corner is another emission nebula - NGC 7538. This is one of the regions of intense star formation easier to observe, due to the fact that it is obscured by dust and dark clouds.The main source of gas ionization in this cloud is the biggest yet discovered protostar which is about 300 times the size of our Solar System.

Star factory NGC 7538

The billowing clouds portrayed in this image from ESA’s Herschel observatory are part of NGC 7538, a stellar nursery for massive stars. Located around 9000 light-years away, this is one of the few regions of massive-star formation that are relatively close to us, allowing astronomers to investigate this process in great detail.

Star factories like NGC 7538 consist mainly of hydrogen gas, but they also contain small amounts of cosmic dust. It was through this minor – but crucial – component that Herschel could image these star-forming regions, because dust shines brightly at the far-infrared wavelengths that were probed by the observatory.

With a total mass of almost 400 000 Suns, NGC 7538 is an active factory where stars come to life – especially huge ones that are over eight times more massive than the Sun. Hundreds of seeds of future stellar generations nestle in the mixture of surrounding gas and dust scattered across the image. Once they reach a critical mass, they will ignite as stars. Thirteen of these proto-stars have masses greater than 40 Suns, and are also extremely cold, less than –250ºC.

One group of stellar seeds seem to trace a ring-like structure, visible in the left part of the image. The ring may be the edge of a bubble carved by previous stellar explosions – as stars reach the end of their lives and explode as dramatic supernovas – but astronomers are still investigating the origin of this peculiar arrangement.

Image credit & copyright ESA/Herschel/PACS/SPIRE. Acknowledgements: Cassie Fallscheer (University of Victoria), Mike Reid (University of Toronto) and the Herschel HOBYS team

Dust Cloud: NGC 7538

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.
 Astronomers often see ring and bubble-like structures in cosmic dust clouds. The strong winds cast out by the most massive stars, called O-type stars, can generate these expanding puffs, as can their explosive deaths as supernovas. But no energetic source or remnant of a deceased O-type star, such as a neutron star, is apparent within the center of the ring. It is possible that a big star blew the bubble and, because stars are all in motion, subsequently left the scene, escaping detection.
 Astronomers study stellar nurseries such as NGC 7538 to better learn how stars come into being. The Herschel observations have revealed numerous clumps of material in NGC 7538, a baker’s dozen of which may evolve into O-type stars. Early in the star-formation process, these clumps remain quite cold, just a few tens of degrees above absolute zero. At these temperatures, the clumps emit the bulk of their radiation in the low-energy, submillimeter and infrared light that Herschel was specifically designed to detect.
 Finding the mysterious ring came as an unexpected bonus during the Herschel observing run. The blue and green colors in this image represent 70- and 160-micron data, respectively, from Herschel’s Photoconductor Array Camera and Spectrometer (PACS) instrument. The red colors are 250-micron observations obtained from Herschel’s Spectral and Photometric Imaging Receiver (SPIRE) instrument.
 Caption: Herschel/Caltech

  ESA/NASA/JPL-Caltech/Whitman College