The Draco Dwarf is a faint dwarf spheroidal galaxy orbiting the Milky Way, a sparse cloud of ancient stars held together mostly by dark matter.
At a glance
| type | galaxy |
|---|---|
| distance from the Sun | 261,000 light-years (80 kpc) |
| its light left it | 261,000 years ago |
| size in the piece | about 2,700 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 Draco Dwarf
The Draco Dwarf is a small satellite galaxy in the direction of the constellation Draco, found by Albert Wilson on photographic plates of the Palomar Sky Survey. It has no gas, no young stars and no spiral structure, only an old, metal-poor population of stars spread so thinly that it is almost invisible against the foreground stars of our own galaxy.
Its stars move faster than their own gravity could account for. Measuring those motions shows that Draco holds far more mass than its starlight implies, which makes it one of the most dark-matter-dominated galaxies known. That makes it a prime target in searches for signals from dark matter particles, and a test for theories of how dark matter clumps on small scales.
What you see in the piece
In the piece it is a loose, faint swarm of old, warm-coloured stars far outside the disc. From the Sun it is lost among the Milky Way’s own stars; fly out and it appears as a diffuse cloud in empty space.
Measured or modelled
How its dark matter is distributed, whether peaked at the centre or spread in a flat core, is debated and depends on the modelling of its stars’ motions.
Questions
How far away is the Draco Dwarf galaxy?
The Draco Dwarf is 261,000 light-years (80 kpc) from the Sun, so the light we see left it 261,000 years ago.
Why is the Draco Dwarf important for dark matter?
The motions of its stars show it contains far more mass than its stars supply, making it one of the most dark-matter-dominated galaxies known.