The Trifid Nebula, M20, is a beautiful gaseous cloud within which new stars are being born. It is one of several spectacular telescopic sights embedded in the summer and autumn Milky Way.
The Trifid is is about 5,000 light-years away, 40 light-years across and a mere 300,000 years old. That makes it one of the youngest star forming regions in our sky, with newborn and embryonic stars embedded in its natal dust and gas clouds.
Trifid Nebula (51 min total exposure Sep 4, 2023)
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The name Trifid 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. Viewed through a small telescope, the Trifid Nebula is a bright and peculiar object, and is thus a perennial favorite of amateur astronomers.
The next image is less enlarged and shows that the Trifid has a nearby sky neighbor, the open star cluster M21 (NGC 6531), sometimes called Webb’s Cross. Although M21 and M20 are similar distances away from us there is no apparent connection between the two. In fact, M21’s stars are much older, about 8 million years old.
Trifid Nebula and M21 (51 min total exposure Sep 4, 2023)
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I’ve not found any other source that mentions it, but to me M21 suggests a diamond ring - a little circle of stars with a bright one just below it.
Besides the dark dust clouds within the Trifid, this region of the sky hosts several other dark nebulae. Besides LdN-232, you will be able to make out several other dark patches where the dust obscures the stars behind them.
One of my earlier blog posts three years ago was also a look at the Trifid Nebula. It’s interesting to compare the earlier image (a five-minute exposure) with the current one (51 minutes); click here to see it.