The Sagittarius Dwarf is a small galaxy being torn apart by the Milky Way, hidden behind the Galactic Centre and trailing a stream of stars around the sky.
At a glance
| type | galaxy |
|---|---|
| distance from the Sun | 65,200 light-years (20 kpc) |
| its light left it | 65,200 years ago |
| size in the piece | about 16,000 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 Sagittarius Dwarf
The Sagittarius Dwarf Spheroidal Galaxy was discovered surprisingly late, because it lies on the far side of the Galactic Centre, behind the dense star fields and dust of the bulge. It was found from the motions of stars that did not share the bulge’s velocities: a separate population, moving as a group.
It is close enough to the Milky Way to be pulled apart by its tides. Stars stripped from it form the Sagittarius Stream, which wraps around the Galaxy in a great loop and has been traced across much of the sky. A massive globular cluster, M54, sits at its heart and may be its nucleus.
It has passed through the Milky Way’s disc several times. Some studies link those passages to bursts of star formation in the disc and to ripples in its outer parts.
What you see in the piece
It appears on the pull-back as a faint, diffuse spread of old yellowish stars on the far side of the Galactic Centre, too dim and scattered to stand out against the bulge from the Sun.
Measured or modelled
Its mass, how many times it has crossed the disc, and how much it shaped the Milky Way’s spiral structure are model-dependent. The extent drawn here is modelled.
Questions
How far away is the Sagittarius Dwarf galaxy?
The Sagittarius Dwarf is about 65,200 light-years (20 kpc) from the Sun, beyond the Galactic Centre.
Why was the Sagittarius Dwarf discovered so late?
It lies behind the centre of the Milky Way, where the bulge’s dense star fields and dust hide it. It was found only through the distinct motions of its stars.