12 December 2016 | Cederblad 214

NGC 7822

Image credit: André van der Hoeven | Click image to enlarge

Image Data

  • Location: Netherlands
  • Date: November 2016
  • Camera: QSI583ws
  • Optics: TMB92SS
  • Filters: Ha, OIII, SII
  • Exposure: A total of 52 exposures of 900s were used (totaling 13 hours) in the different bands.

Cederblad 214 is one of the largest molecular cloud complexes in the Milky Way. It forms a large region of glowing hydrogen gas together with NGC 7822, another famous hydrogen nebula in this region. In the center of this region lies the young star cluster named Berkeley 59. This complex has a distance of about 900 parsecs from Earth.

The central star cluster in the nebula is quite young with the oldest stars forming some 5 million years ago. The central star, named BD+66 1673, lies on the northwestern edge of Berkeley 59. This star was classified as an O5-type star in 2008, which means it has a surface temperature of about 45 000 K and a luminosity of over 100 000 times that of the Sun. This makes this star the hottest star within a globe of 1000 pc surrounding our Sun. Because of this high temperature this star generates high velocity stellar winds that formed an immense 200 light-year diameter shell of molecular gas which contacts the surrounding cold molecular cloud. Also the darker, cold molecular pillars on the edge of the cloud are formed by this process. During the research the star was investigated for brightness variations and a periodical curve with a period of 5.33146 days was measured. The light-curve showed periodic dips which confirmed that the star is a binary star of the Algol type with a companion star of the B-type.

In the complex, a number of bright-rimmed globules can be found. They are formed by complicated interactions of gas, dust and radiation. The radiation and stellar winds of young, massive stars slowly evaporate and destroy the parent molecular cloud from which they formed over a time scale of about 10 million years. First, the lower density gas in the cloud is pushed away, leaving higher density clumps of gas and dust which resist the pressure forming dark globules that are energized by the ultra-violet radiation of nearby stars. The surface of the globules becomes ionized, and starts to glow, forming the bright edge of the globule. Finally a new generation of low mass stars can form within the globule as it becomes compressed by the radiation and winds of the nearby stars. The lifetime of the globule is quite short, tending to evaporate away within 500 000 years.

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