WR 102

Sagittarius IAU.svg
Författare/Upphovsman: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg), Licens: CC BY 3.0
IAU Sagittarius chart

Golden star.svg
(c) I, Ssolbergj, CC BY 3.0
Gold-shaded star.

Compare of WR 102 and Sun.png
Författare/Upphovsman: NASA and Typhoon2021, Licens: CC BY-SA 4.0
Compare WR 102 and Sun.

WR102 Ejecta Nebula.png
Författare/Upphovsman: Judy Schmidt from Fresh Meadows, NY, USA, Licens: CC BY 2.0

This nebula near the top left edge of the widefield Milky Way mosaic caught my eye. It looks different from most of the other nebulas, because its emissions are so strongly in the MIPS1 channel with very little or none appearing in the other two. So in my other image, it appears extremely red. For this version, I have processed it in a way that makes it easier to see by having it screen over the green and blue channels a bit.

Anyway, one thing I have been struggling with for infrared imagery is how to interpret the various bands. Is it dust? Is it gas? What kind of dust? What kind of gas? Trying to learn more about this nebula, I came across this paper which helps me understand why it's been difficult. If I've understood it correctly, the authors looked at the emissions of known objects and compared them to the WISE W3 and W4 bands to see what matches up. In particular, the W4 band is closely associated with Hα emission for certain objects like this one, and the W4 band is very close to Spitzer's MIPS1 band presented here, so I'm satisfied to say this could probably also a Hα emission nebula.

The curling, looping appearance is unfamiliar to me. I don't know if those are actual loops or if they just look like loops from here. Note that the star itself, WR102, is nearly invisible in this image.

Pale Orange: Spitzer/MIPS1 (24μm) Green: WISE/W3 (12μm) Blue: Spitzer/IRAC4 (8μm)

North is NOT up. It is 58.7° counter-clockwise from up.