Cassiopeia A

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Cassiopeia A

An intense radio source 2.8 kiloparsecs distant in the constellation Cassiopeia. It has the largest flux density at low frequencies of all the discrete radio sources (apart from the Sun), the value being about 8200 jansky at 178 megahertz, and a spectral index of –0.77. The flux drops by about 1% per year. It is a supernova remnant – probably of a supernova explosion (unrecorded) of a massive (˜50 MO) star in the late 17th century – and has a ringlike structure about four arc minutes in diameter. The radio radiation is by synchrotron emission and the radio shell is expanding at 2300 km s–1. It is also an extended source of soft X-rays.

Cassiopeia A

[‚kas·ē·ə′pē·ə ′ā]
(astronomy)
One of the strongest discrete radio sources, located in the constellation Cassiopeia, associated with patches of filamentary nebulosity which are probably remnants of a supernova.
References in periodicals archive ?
The NuSTAR map of Cas A shows the titanium concentrated in clumps at the remnant's center and points to a possible solution to the mystery of how the star met its demise.
Previously, it was hard to interpret what was going on in Cas A because the material that we could see only glows in X-rays when it's heated up.
Two independent research teams studied the supernova remnant Cassiopeia A, or Cas A for short, the remains of a massive star 11,000 light-years away that would have appeared to explode about 330 years ago as observed from Earth.