CTB 109 is a supernova remnant in Cassiopeia shaped like a half-moon, its shell cut short by a molecular cloud, with a magnetar at its centre.
At a glance
| type | supernova remnant |
|---|---|
| distance from the Sun | 10,400 light-years (3.2 kpc) |
| its light left it | 10,400 years ago |
| size in the piece | about 85 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 CTB 109
CTB 109 is the expanding remnant of a stellar explosion in the Perseus Arm. In X-rays and radio it shows a semicircular shell: on one side the blast wave has met a dense molecular cloud and stalled, so the shell is missing there and the remnant looks cut in half.
Near its centre sits an anomalous X-ray pulsar, a slowly spinning neutron star whose glow is thought to be powered by the decay of an enormous magnetic field rather than by its spin. Objects of this kind are called magnetars, and CTB 109 is one of the few remnants where a magnetar and its birthplace can be studied together. It also counts among the clearest cases of a remnant whose shape is set by its surroundings.
What you see in the piece
In visible light it is lost among the stars of Cassiopeia; in the X-ray and radio bands its half shell appears.
Questions
Why is CTB 109 a half circle?
Its blast wave ran into a dense molecular cloud on one side and was stopped, so only half of the shell is seen.
How far away is CTB 109?
CTB 109 is about 10,400 light-years (3.2 kpc) from the Sun.