Trifid Nebula

Trifid Nebula
Emission nebula
H II region
reflection nebula and dark nebula

Trifid Nebula by the Hubble Space Telescope
Credit: NASA/ESA
Observation data: J2000 epoch
Right ascension 18h 02m 23s[1]
Declination −23° 01′ 48″[1]
Distance 5200[2] ly   (1,600 pc)
Apparent magnitude (V) +6.3[1]
Apparent dimensions (V) 28 arcmins
Constellation Sagittarius
Physical characteristics
Radius 21 ly
Designations M20, NGC 6514,[1] Sharpless 30, RCW 147, Gum 76

The Trifid Nebula (catalogued as Messier 20 or M20 and as NGC 6514) is an H II region located in Sagittarius. It was discovered by Charles Messier on June 5, 1764.[3] Its name means 'divided into three lobes'. The object is an unusual combination of an open cluster of stars; an emission nebula (the lower, red portion), a reflection nebula (the upper, blue portion) and a dark nebula (the apparent 'gaps' within the emission nebula that cause the trifurcated appearance; these are also designated Barnard 85). Viewed through a small telescope, the Trifid Nebula is a bright and peculiar object, and is thus a perennial favorite of amateur astronomers.[4]

The Trifid Nebula is a star-forming region in the Scutum spiral arm of the Milky Way.[5] The most massive star that has formed in this region is HD 164492A, an O7.5III star with a mass more than 20 times the mass of the Sun.[6] This star is surrounded by a cluster of approximately 3100 young stars.[7]

Characteristics

The Trifid Nebula was the subject of an investigation by astronomers using the Hubble Space Telescope in 1997, using filters that isolate emission from hydrogen atoms, ionized sulfur atoms, and doubly ionized oxygen atom. The images were combined into a false-color composite picture to suggest how the nebula might look to the eye.

The close-up images show a dense cloud of dust and gas, which is a stellar nursery full of embryonic stars. This cloud is about 8 ly away from the nebula's central star. A stellar jet protrudes from the head of the cloud and is about 0.75 ly long. The jet's source is a young stellar object deep within the cloud. Jets are the exhaust gasses of star formation and radiation from the nebula's central star makes the jet glow.

The images also showed a finger-like stalk to the right of the jet. It points from the head of the dense cloud directly toward the star that powers the Trifid nebula. This stalk is a prominent example of evaporating gaseous globules, or 'EGGs'. The stalk has survived because its tip is a knot of gas that is dense enough to resist being eaten away by the powerful radiation from the star.

In January 2005, NASA's Spitzer Space Telescope discovered 30 embryonic stars and 120 newborn stars not seen in visible light images.

It is approximately 5000 ly away from Earth. Its apparent magnitude is 6.3.

See also

References

  1. 1 2 3 4 "SIMBAD Astronomical Database". Results for NGC 6514. Retrieved 2006-11-16.
  2. ↑ "Star formation in the Trifid Nebula" (PDF). Astronomy & Astrophysics. 489: 157–171. 2008. Bibcode:2008A&A...489..157L. arXiv:0809.2023 Freely accessible. doi:10.1051/0004-6361:200810079. Retrieved 2011-10-09.
  3. ↑ Messier 20
  4. ↑ "Science Daily". Science Daily article on Trifid Nebula. Retrieved 2010-07-06.
  5. ↑ Cambrésy, L.; et al. (2011). "Variation of the extinction law in the Trifid nebula". Astronomy & Astrophysics. 527: A141. Bibcode:2011A&A...527A.141C. arXiv:1101.1089 Freely accessible. doi:10.1051/0004-6361/201015863.
  6. ↑ Rho, J.; et al. (2004). "Chandra Observation of the Trifid Nebula: X-Ray Emission from the O Star Complex and Actively Forming Pre-Main-Sequence Stars". Astrophysical Journal. 607 (2): 904–912. Bibcode:2004ApJ...607..904R. arXiv:astro-ph/0401377 Freely accessible. doi:10.1086/383081.
  7. ↑ Kuhn, M. A.; et al. (2015). "The Spatial Structure of Young Stellar Clusters. II. Total Young Stellar Populations". Astrophysical Journal. 802 (1): 60. Bibcode:2015ApJ...802...60K. arXiv:1501.05300 Freely accessible. doi:10.1088/0004-637X/802/1/60.

Coordinates: 18h 02m 23s, −23° 01′ 48″

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