G21.5-0.9 is a young supernova remnant in Scutum, dominated by a bright pulsar wind nebula and used to calibrate X-ray telescopes in orbit.
At a glance
| type | supernova remnant |
|---|---|
| distance from the Sun | 15,300 light-years (4.7 kpc) |
| its light left it | 15,300 years ago |
| size in the piece | about 18 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 G21.5-0.9
G21.5-0.9 belongs to the composite remnants: a compact nebula of particles blown by a central pulsar, surrounded by a much fainter outer shell. The nebula is bright, compact and steady, which is why it became a standard calibration target for the Chandra X-ray Observatory, observed again and again over its mission.
Those repeated observations paid off: added together, they revealed the faint shell and other structure around the bright core. A young pulsar powering the nebula was later found in radio. Its name is simply its position in Galactic coordinates, the way many remnants hidden in the disc are known.
What you see in the piece
Small even at this scale and hidden by dust in visible light; the X-ray band is the way to find it.
Questions
Where does the name G21.5-0.9 come from?
It is the object’s position in Galactic longitude and latitude, the usual way of naming remnants that have no common name.
How far away is G21.5-0.9?
G21.5-0.9 is about 15,300 light-years (4.7 kpc) from the Sun.