Swimming pools in space.
In the constellation of Sagittarius, a few celestial degrees apart, we find the large Lagoon Nebula (M8, 4,100 light years away, 110 across) and the nearby Trifid Nebula (M20, 5,200 light years away, 21 across).
The first is reminiscent of a huge lagoon, and anything but a relaxed one: powerful stellar winds of dust and ionized hydrogen. The name comes from the dark band of dust that crosses it and seems to divide it like a stretch of water. At its centre the star Herschel 36 and the cluster NGC 6530 light the gas; in the denser parts you can pick out Bok globules, dark cocoons of dust inside which new stars are forming. It is one of the few star-forming regions visible to the naked eye: an elongated smudge in the densest part of the summer Milky Way, towards the centre of our galaxy.
The Trifid owes its name to the presence of no fewer than three kinds of nebulosity. The red marks a dominant hydrogen emission, ionized by a single central star. The blue is the effect of dust reflecting the ionized oxygen radiation of that same star. And finally the dark parts — split into three bands, hence the name — are dense sites of star formation.
That is exactly what makes it a rare object: it shows at once both ways a nebula can shine, by its own light and by reflected light.
← Back to the gallery