W44 is a supernova remnant in Aquila crashing into a molecular cloud, one of the sites where gamma rays showed supernovae accelerate cosmic-ray protons.
At a glance
| type | supernova remnant |
|---|---|
| distance from the Sun | 9,780 light-years (3 kpc) |
| its light left it | 9,780 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 W44
W44 takes its name from the Westerhout catalogue of radio sources. It belongs to the class of mixed-morphology remnants: a shell in radio, but in X-rays filled at its centre with hot gas, rather than brightest at its rim.
On one side the blast is running into a molecular cloud. The Fermi telescope found there, as in IC 443, the gamma-ray signature of accelerated protons striking dense gas, strong evidence that supernova remnants are where cosmic-ray protons are born. A pulsar with its own small wind nebula lies within the remnant.
What you see in the piece
It is drawn as a shell of shocked gas close to the Galactic plane, dimmed by dust in visible light; it shows in the radio band and, where the shock meets the cloud, in gamma rays.
Measured or modelled
Why mixed-morphology remnants are filled with X-ray gas at their centres is still debated. The drawn extent is modelled.
Questions
Why is W44 important?
Gamma rays from where its shock meets a molecular cloud show the signature of accelerated protons, evidence that supernova remnants produce cosmic rays.
How far away is W44?
W44 is about 9,780 light-years (3 kpc) from the Sun, in Aquila.