July 2025 - Picture of the Month
Emission nebula Sh2-106 in Cygnus
I've chosen a wonderful image of an object from Stewart Sharpless that's high in northern skies this month: Sh2-106 in his catalogue (aka the Celestial Snow Angel). This H-II region lies about 2,000 light-years from us in the constellation of Cygnus and was formed only 3,500 years ago from its parent molecular cloud.
Sh2-106 is an emission nebula that's ionised by a 15 solar mass O8 type star, S106 IRS 4 (Infrared Source 4), hidden at it's heart in the centre of this image. It's bipolar hourglass shape makes this object look like a planetary nebula, and it's due to a ring of dust and gas in orbit around IRS 4 limiting local radial expansion.
I particularly like the rippled texture of the nebula's "wings" which is caused by interaction between the high velocity outflows and the surrounding interstellar medium.
At the other end of the stellar scale, studies of Sh2-106 in the infrared wavelength have revealed hundreds of brown dwarf stars that weight less than 0.1 solar masses and as a result have remained sub-stellar: a cluster of brown dwarves, not massive enough to fuse hydrogen.
James Whinfrey - Website Administrator.
