The Trifid Nebula (M20) is a young nebula in Sagittarius where a red cloud of glowing gas, split by dark lanes of dust, sits beside a blue one.
At a glance
| type | nebula |
|---|---|
| distance from the Sun | 5,220 light-years (1.6 kpc) |
| its light left it | 5,220 years ago |
| size in the piece | about 39 light-years acrossmodel |
Read off the piece’s own catalogue, the same values it draws with. Model marks a property of the piece’s galaxy model rather than a measurement.
About Trifid Nebula (M20)
The Trifid puts several kinds of nebula in one view. The red part is an emission nebula, hydrogen ionised by a young massive star near its centre. Dark lanes of dust lie in front of it and divide it into the lobes that gave it its name.
To the north is a reflection nebula: dust that makes no light of its own but scatters the light of a nearby star, and looks blue for the same reason the daytime sky does.
Hubble’s images show pillars of gas being worn away by the central star, and from the tip of one of them a narrow jet streaming out of a star still forming inside it.
What you see in the piece
Fly to it and the lanes come away from the glow: they are dust lying in front of it. Above, the blue cloud shines by scattered starlight, and on the rim a pillar points at the central star with a thin jet at its tip.
Measured or modelled
Its distance is uncertain, and how the lanes and the blue cloud sit along the line of sight is modelled.
Questions
Why is the Trifid Nebula red and blue?
The red part is hydrogen glowing because a hot star ionises it. The blue part is dust scattering starlight, and scattering favours blue light.
Why is it called the Trifid?
Dark lanes of dust cross its glowing part and divide it into lobes, so it looks split in three.