The Coalsack is the most prominent dark nebula in the sky, a cloud of cold dust beside the Southern Cross that blots out the bright Milky Way behind it.
At a glance
| type | nebula |
|---|---|
| distance from the Sun | 587 light-years (180 pc) |
| its light left it | 587 years ago |
| size in the piece | about 59 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 Coalsack
A dark nebula is a cloud of gas and dust dense enough to absorb the light of the stars behind it. The Coalsack has no stars of its own to light it, so it shows only as a hole: a dark patch cut out of one of the richest parts of the southern Milky Way, between Crux and Centaurus. It is plain to the naked eye from a dark site.
The dust grains that make it dark are tiny, and they dim blue light more than red, so the few background stars that do shine through are reddened. Clouds like this are cold and quiet, the raw material from which stars may later form, although the Coalsack itself shows little sign of forming stars now.
In Aboriginal Australian astronomy the Coalsack is the head of the Emu in the Sky, a figure traced not by stars but by the dark lanes of dust that run along the Milky Way.
What you see in the piece
It is drawn as dust that absorbs rather than shines, so it appears only as a shadow against the stars and glow beyond it; switch to infrared and the dust goes transparent.
Measured or modelled
Its depth and shape along the line of sight are modelled; only its outline on the sky and an approximate distance are measured.
Questions
What is the Coalsack Nebula?
It is a dark cloud of interstellar dust next to the Southern Cross. It absorbs the light of the Milky Way stars behind it, so it looks like a dark patch in the band.
How far away is the Coalsack?
The Coalsack is about 587 light-years (180 pc) from the Sun.