NGC 6357

Not to be confused with Omega Nebula.

NGC 6357 is a diffuse nebula near NGC 6334 in the constellation Scorpius. The nebula contains many proto-stars shielded by dark discs of gas, and young stars wrapped in expanding "cocoons" or expanding gases surrounding these small stars. It is also known as the Lobster Nebula.^[4][5] This nebula was given the name War and Peace Nebula by the Midcourse Space Experiment scientists because of its appearance, which, in infrared images the bright, western part resembles a dove, while the eastern part looks like a skull.^[6] A petition by anime fans to rename it as the Madokami nebula, due to resemblance with a character, was unsuccessful.^[7][8]

NGC 6357

Emission nebula
H II region
NGC 6357 composite image
Observation data: J2000 epoch
Right ascension	17h 24m [1]
Declination	−34° 20′[1]
Distance	~5900±450[2] ly   (1800±140 pc)
Constellation	Scorpius[3]
Designations	War and Peace Nebula,[1] Lobster Nebula [4] Sharpless 11, RCW 131, Gum 66, Madokami
See also: Lists of nebulae

It is located about 5,500 light years away from Earth.^[9] NGC 6357 is connected by a filamentary structure to NGC 6334, and the two may form a single complex.^[10]

Associated open clusters

Pismis 24

A Hubble Space Telescope (HST) image of Pismis 24-1, the "core" of NGC 6357.

Dark Energy Camera captures the star-forming nebula NGC 6357

This nebula includes the open cluster Pismis 24, which is home to several massive stars. One of the brightest stars in the cluster, Pismis 24-1, was thought possibly to be the most massive on record, approaching 300 solar masses, until it was discovered to be a multiple system of at least three stars; component stars would still remain near 100 solar masses each, making them among the more massive stars on record.^[11][12]

G353.2+0.7

The young stellar cluster G353.2+0.7 lies east of Pismis 24 and was revealed by a Chandra X-ray image showing approximately 800 stars.^[13]

G353.1+0.6

The young stellar cluster G353.1+0.6 lies southeast of Pismis 24 and also contains approximately 800 stars detected by X-ray.^[13] The region includes several O-type stars, including [BDSB2003] 10.^[14]

Massive stars

NGC 6357 is one of the most prominent sites of massive-star formation in our neighborhood of the Milky Way. A variety of early O-type stars reside in this nebula, blowing the bubbles around the star clusters that can be seen in the molecular cloud.

Prominent stars in Pismis 24^[15]

Star name	Spectral type	Magnitude (Mbol)	Temperature[16] (K)	Radius (R☉)	Mass (M☉)
WR 93 (HD 157504)	WC7	-11.2	71,000	10	120
Pismis 24-1NE	O3.5 If*	−10.0	42,000	17	74
Pismis 24-1SW	O4 III	−9.8	41,500	16	66
Pismis 24-2	O5.5 V(f)	−8.9	40,000	12	43
Pismis 24-3	O8 V	−7.7	33,400	9	25
Pismis 24-10	O9 V	−7.2	31,500	8	20
Pismis 24-12	B1 V	−5.3	30,000	4	11
Pismis 24-13	O6.5 III((f))	−8.6	35,600	12	35
Pismis 24-15	O8 V	−7.8	33,400	10	25
Pismis 24-16	O7.5 V	−9.0	34,000	16	38
Pismis 24-17	O3.5 III	−10.1	42,700	17	78
Pismis 24-18	B0.5 V	−6.4	30,000	6	15
Pismis 24-19	B0.5 V	−5.4	30,000	4	11

See also

• List of most massive stars
• Sharpless Catalog
• RCW Catalogue
• Gum Catalog