APOD: 2026 February 6 - Supernova Remnant Cassiopeia A

Good Red Friday evening, Rallypoint, and welcome to the February 6, 2026 edition of Astronomy Picture of the Day (APOD).

A regular member of the APOD family, Cassiopeia A is a supernova remnant in the northern constellation Cassiopeia. It is also the most luminous extra-solar radio source in the sky at frequencies above 1 GHz. The supernova occurred only 11,000 light-years away from Earth. Researchers think the light from this event first reached Earth in the 1660s.

Some believe that Astronomer Royal John Flamsteed may have first observed the supernova on August 16, 1680, when he catalogued a sixth-magnitude star at a previously unknown position. In 2013, astronomers detected the presence of phosphorus, confirming the theory that heavier elements are likely produced through a process called supernova nucleosynthesis. Today's infrared image of Cassiopeia A was captured by the Webb Space Telescope in 2023.