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The Trifid Nebula (Greenhouse in the Sky)

Within the nebula-rich constellation of Sagittarius lies the Trifid Nebula (M20 or NGC 6514). The word trifid means 'divided in three'. This stellar nursery has been a favorite of amateur astronomers for years, as it is a bright, colorful object when viewed through a small telescope.

Photo Credit: NASA, JPL-Caltech, J. Rho (SSC/Caltech)

The nebula was first observed by Charles Messier in June 1764; the hazy, glowing object was listed as simply M20 in the Messier Catalogue. The English astronomer John Herschel, while observing the nebula some 60 years later, noticed the dust lanes that seem to separate the cloud into three separate lobes. Herschel then named the nebula Trifid.

Trifid, unlike most nebulae, is actually a rare combination of three different types of nebulae, in addition to open star clusters.

In the upper left corner of Trifid is a reflection nebula. Reflection nebulae, as the name implies, are dust clouds that merely reflect the light that is emitted by nearby stars. These nebulae tend to be light and wispy, somewhat similar to the airiness of a mare's tail cloud. As these reflection nebulae are not dense, stars can be seen through the cloud's dust. Star formations have been known to develop within reflection nebulae.

The area that appears orange in the picture above and pink in the pictures below, is an emission nebula. Emission nebulae are clouds made up of ionized gas. A hot star emitting high-energy photons close to a nebula is one of the most common sources of ionization. The emission nebula within Trifid is an H II region, an area that has shown recent star formation.

The bands seen within Trifid are dark nebulae. Dark nebulae are so dense that light from surrounding stars and other nebulae cannot be seen through the cloud that makes up the nebula. These clouds which make up dark nebulae are the breeding ground of new stars and planets.

This combination of three different star-breeding nebulae within Trifid is akin to a greenhouse. Over time, many new stars will undoubtedly emerge from this hotbed of stellar activity.

Photo Credit: ESO

To the left of the "heart" of Trifid is a finger-like cloud formation (seen clearly in the two lower pictures) which points to the star that powers the nebula. This gas protrusion from the cloud is a well-defined example of an "EGG", or evaporating gaseous globule. The white spot at the tip of the "finger", resembling a star, is actually an extremely dense knot of gas; so dense that it is able to avoid being obliterated by the massive radiation put out by Trifid's central star.

Photo Credit: Hunter Wilson

Just half a degree south of Trifid is the Lagoon Nebula, another favorite of astrophotographers, also located in the constellation Sagittarius.

*** Note: Although the colors are markedly different between the top and two bottom pictures, these are all pictures of the Trifid Nebula. The color variances are due to a number of factors, including the equipment used for taking the photographs and filters that may have been applied during the taking of the pictures.

For Help Locating This Object in the Sky: Use the Interactive Messier Map in the upper right hand corner. Objects are listed numerically. Click on the object you wish to view (ex. The Crab Nebula is M1) and a map will be displayed showing that object's location.

Author Resource: Written by Starr Hendon


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