Sh 2-4 is an emission nebula in the constellation Scorpius. It is part of the Sharpless Catalog assembled by Stewart Sharpless.[4] It was originally misidentified as a planetary nebula. The incorrect planetary designation PN H 2-6 can still be used as an identifier. It may be associated with the star cluster Havlen-Moffat 1.[1]
Visibility
The nebula is bright, and visible with longer exposure. The nebula mostly emits red light, making viewing through a hydrogen-alpha filter effective.[5]
Structure
Havlen-Moffat 1 is known to be a source of ionization within Sh 2-4. The nebula contains two Wolf-Rayet stars, designated WR 87 and WR 89.[6] Contained within the nebula is the infrared cluster [DBS2003] 118. [7]
References
- ^ a b “The Sharpless Observing Atlas” (PDF).
- ^ “Sharpless (Sh2) – Astrobasics”. 13 September 2022.
- ^ “RCW 121”.
- ^ “CCD Images of the Sharpless Catalog”.
- ^ “SH2-4 (Sharpless 4)”.
- ^ “RCW 121”.
- ^ Dutra, C. M.; Bica, E.; Soares, J.; Barbuy, B. (2003). “New infrared star clusters in the southern Milky Way with 2MASS”. Astronomy and Astrophysics. 400 (2): 533. arXiv:astro-ph/0301221. Bibcode:2003A&A…400..533D. doi:10.1051/0004-6361:20030005.
