Trifid Nebula

The Trifid Nebula is a star-forming region in Sagittarius about 5,000 light-years away, where dark dust lanes divide glowing gas into three prominent lobes.

Emission nebula: An interstellar cloud that emits light after its gas is ionized, usually by nearby hot stars. The Trifid’s red glow comes from ionized hydrogen in its emission-nebula region.
Ionization front: A moving boundary between ionized gas and neutral gas, driven by energetic radiation. Radiation from massive young stars advances into the Trifid’s surrounding neutral material.
Lagoon Nebula: A large star-forming nebula in Sagittarius, also cataloged as Messier 8. Like the Trifid, it is a prominent Sagittarius nebula shaped by young stars and glowing gas.
Charles Messier: An eighteenth-century French astronomer known for compiling a catalog of nebulae and star clusters. Messier included the Trifid as object 20 in his catalog.
Reflection nebula: A dust cloud that appears bright by scattering light from nearby stars. Blue light scattered by dust gives the Trifid’s northern region its reflection-nebula appearance.
Radiation-driven implosion: The compression and collapse of a dense gas clump under intense radiation from nearby stars. Radiation may compress dense Trifid globules and help trigger star formation within them.
Eagle Nebula: A star-forming nebula in Serpens that includes the Pillars of Creation. Its sculpted gas pillars offer a well-known comparison for radiation-shaped structures in the Trifid.
Messier catalog: A catalog of astronomical objects compiled by Charles Messier and later expanded by other astronomers. The Trifid’s designation, M20, places it among the catalog’s nebulae and clusters.
Dark nebula: A dense cloud of interstellar dust and gas that blocks light from objects behind it. Dark dust lanes cut across the bright nebula and create its three-part outline.
Bok globule: A small, dense cloud of gas and dust that can contain collapsing protostars. Dark compact globules within the nebula are potential sites of ongoing stellar birth.

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