APOD: In the Center of the Trifid Nebula (2020 Nov 01)

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APOD: In the Center of the Trifid Nebula (2020 Nov 01)

Post by APOD Robot » Sun Nov 01, 2020 4:05 am

Image In the Center of the Trifid Nebula

Explanation: What's happening at the center of the Trifid Nebula? Three prominent dust lanes that give the Trifid its name all come together. Mountains of opaque dust appear near the bottom, while other dark filaments of dust are visible threaded throughout the nebula. A single massive star visible near the center causes much of the Trifid's glow. The Trifid, cataloged as M20, is only about 300,000 years old, making it among the youngest emission nebulas known. The star forming nebula lies about 9,000 light years away toward the constellation of the Archer (Sagittarius). The region pictured here spans about 10 light years. The featured image is a composite with luminance taken from an image by the 8.2-m ground-based Subaru Telescope, detail provided by the 2.4-m orbiting Hubble Space Telescope, color data provided by Martin Pugh and image assembly and processing provided by Robert Gendler.

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Re: APOD: In the Center of the Trifid Nebula (2020 Nov 01)

Post by Ann » Sun Nov 01, 2020 10:36 am

Two parts of the Trifid Nebula are particularly interesting:

The Trifid Nebula is ionized by a small group of hot stars near its very center.
Wikipedia wrote:

The Trifid Nebula (catalogued as Messier 20 or M20 and as NGC 6514) is an H II region located in Sagittarius. (...) 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).
The Trifid Nebula is a star-forming region in the Scutum spiral arm of the Milky Way. 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. This star is surrounded by a cluster of approximately 3100 young stars.
According to Simbad, HD 164492 is a pre-main sequence star of spectral class O7.5Vz. Don't ask me what the "z" means. Anyway, Simbad suggests that HD 164492 is so young that it may not yet have initiated hydrogen fusion in its core. (I find that last claim just a little bit hard to believe.)

The picture at right does a better job than the APOD at showing which of the bright star at the center of the Trifid Nebula is HD 164492A. Please note the bright rim of the stubby dust pillar close to the small group of stars. Its bright rim means that it is being directly illuminated by the hot stars. Also note the bright outflow from the top of this stubby pillar. A new star is almost certainly being born here, but it is hidden by the dust pillar from our point of view.

Another dust pillar in the Trifid Nebula features two jets. Clearly two young stars are being born here, and during their birth pangs they emit long narrow jets.

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Re: APOD: In the Center of the Trifid Nebula (2020 Nov 01)

Post by VictorBorun » Sun Nov 01, 2020 1:10 pm

I wonder whether the foreground narrow cone is a jet from a forming star in the depth of the dense dust dome.
I mean, a jet that is getting narrower to the end of it. Could it be sharpened by the stellar wind or radiation emitted by the main stars at the center of the APOD picture?

The same kind of sharpening may be being done to a two-lobed nebula at the left side of the last picture, more so at the top lobe.

By the way, is there 2 shadows cast behind that narrow cone on the dome by the 2 main stars ?
If so, why do they look so narrow? Or is the cone more narrow than it seems — is it in fact pointing toward us at 10° and looking fatter?