Key Takeaways:
- Sharpless 2–157, an emission nebula situated in the constellation Cassiopeia and informally known as the Lobster Claw Nebula, is infrequently targeted by amateur astronomers despite its distinct morphology and adjacency to the prominent Bubble Nebula (NGC 7635).
- Two open star clusters are associated with Sharpless 2–157: Markarian 50, estimated to be 11,000 light-years distant and 7.5 million years old, and NGC 7510.
- NGC 7510, located near the northern periphery of the nebula, presents an apparent magnitude of 8, spans 7 arcminutes, is also 11,000 light-years distant, and has an estimated age of 10 million years.
- A localized region within Sharpless 2–157, designated Sharpless 2–157a, contains a circular nebula that is ionized by the luminous Wolf-Rayet star WR 157 embedded within it.
As we’ve seen in recent posts, the northern constellation Cassiopeia is chock-full of intriguing nebulae and bright star clusters. A large and relatively bright emission nebula among this group, Sharpless 2–157, is rarely observed by amateur astronomers. It is sometimes called the Lobster Claw Nebula due to its distinctive shape.
This big nebula lies in relatively close proximity to the well-known and frequently observed Bubble Nebula (NGC 7635).
Two open clusters lie within or close to Sharpless 2–157. They are Markarian 50, which lies 11,000 light-years away and is 7.5 million years old, and, near the northern edge of the nebula, the bright cluster NGC 7510. The latter glows at 8th magnitude, spans 7’, lies 11,000 light-years away, and is about 10 million years old.
The northern part of Sharpless 2–157, sometimes identified as Sharpless 2–157a, contains a circular nebula surrounding a Wolf-Rayet star, WR 157, which is ionizing the surrounding gas.
