Object of the Week, 24 Dec 2017 -- Sh2-302 - The snowman nebula

[obrazell]

Snowman nebula Sh 2-302, Gum 6, LBN 1046, RCW 7

RA: 07h 31.517m

Dec: -16° 58.00'

Size: 17.8'x14.0'

Given the seasonal nature of this OOTW I thought what better target than the emission nebula Sh 2-302, popularly known as the Snowman nebula.

sh2-302_DSS.jpg

Discovered by Stewart Sharpless and included in his 1959 catalogue it had already been independently found and catalogued earlier by Colin Gum in 1955 and given the number Gum 6. Sh2-302 is a star forming and emission region on the front side of the molecular cloud JKK96A and the nebula is probably ionised by the star HD 59986 and the stars of the open cluster Bochum 5, although there is some debate over the spectral type of HD 59986 and whether it is hot enough to ionize the nebula. The nebula also contains an infrared cluster that was discovered on 2MASS images and is also a site of active star formation as seen in the WISE image.

sh2-302_WISE.jpg

There is also the reflection nebula, vdB 97, associated with the nebula. Sh2-302 would appear to be well in front of the expanding HI super shell GS234-0.2 and is thought to be about 1800 pc away. The popular name the Snowman comes from the dark lane bisecting the nebula, appearing to make a head and body. Sh2 -302 falls in the upper reaches of the constellation of Puppis, not much below the declination of Sirius so even from northern latitudes it may be high enough to give decent views. Given its size and faintness the nebula will probably require a wide field eyepiece and a UHC type filter. The nebula does have some observations included in the NSOG Vol. 1 with a 16/18 inch telescope and they describe it as faint with an OIII filter. I must admit I am surprised that they used an OIII rather than a UHC filter to observe it. Other observations I have seen suggest it may respond to using an H-beta filter.
Nearby there is also the star cluster Bochum 4. The included chart gives the designations for objects in the area.

sh2-302.pdf

As Always

“Give it a go and let us know”

Owen Brazell
Editor Webb DSO
22" Obsession UC
15" Obsession UC

[Steve Gottlieb]

I haven't looked at this Sharpless, but I'm curious about other observations. I notice Reiner Vogel called it an "extremely faint glow" with his 22" and a H-beta filter. Assuming it's an H-beta object, the OIII observation seems odd.