Messier Index/M20

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Trifid Nebula
Trifid.nebula.arp.750pix.jpg
Trifid Nebula by the w:Hubble Space Telescope (w:NASA/w:ESA)
Observation data: w:J2000 epoch
Type Emission/Reflection
Right ascension 18h 02m 23s[1]
Declination -23° 01′ 48″[1]
Distance 2000 - 9000 ly
Apparent magnitude (V) +6.3[1]
Apparent dimensions (V) ~20 arcmins
Constellation Sagittarius
Physical characteristics
Radius -
Absolute magnitude (V) -
Notable features -
Other 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 w:H II region located in Sagittarius. Its name means 'divided into three lobes'. The object is an unusual combination of an w:open cluster of w:stars, an w:emission nebula (the lower, red portion), a w:reflection nebula (the upper, blue portion) and a w:dark nebula (the apparent 'gaps' within the emission nebula that cause the trifid appearance; these are also designated Barnard 85). Viewed through a small w:telescope, the Trifid Nebula is a bright and colorful object, and is thus a perennial favorite of amateur astronomers.

Characteristics

The Trifid Nebula was the subject of an investigation by astronomers using the w:Hubble Space Telescope in w:1997, using filters that isolate emission from w:hydrogen w:atoms, w:ionized w:sulfur atoms, and doubly ionized w:oxygen atoms. 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 w:stellar nursery full of embryonic stars. This cloud is about 8 w:light years away from the nebula's central star. A w:stellar jet protrudes from the head of the cloud and is about 0.75 w:light-years long. The jet's source is a young stellar object deep within the cloud. Jets are the exhaust gasses of star formation. 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 an w: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, w:NASA's w:Spitzer Space Telescope discovered 30 embryonic stars and 120 newborn stars not seen in w:visible light images.

Gallery

External links

References

  1. a b c d "SIMBAD Astronomical Database". Results for NGC 6514. http://simbad.u-strasbg.fr/Simbad. Retrieved 2006-11-16.