On June 65438+1October1day, 2022, NASA began to observe luminous creatures as beautiful as the bottom of the sea in the target Cassiopeia A.

65438+1October 1 1, IXPE began to observe its first official scientific target: Cassiopeia A, which is the remains of a massive star that exploded about 350 years ago (from the perspective of the earth). This photo shows Cassiopeia A, another orbiting observatory, which is helping us solve the mystery of outer space.

Cassiopeia A (Cas A) is a supernova remnant (SNR) in Cassiopeia and the brightest radio wave source outside the solar system. Its frequency in the sky is higher than 1GHz. This supernova is in the Milky Way galaxy, about 1 1000 light-years (3,400 parsec) [2][3]. From the position of the earth, the cloud gas formed by the expansion of the material left over by supernovae is now about 10 light-year (3 parsec). In the field of amateur astronomy, with a telescope with a diameter of 234mm(9.25 inches) and appropriate filters, observations can already be made at the wavelength of visible light [4].

It is estimated that the light generated by the explosion of this star first reached the earth about 300 years ago, but there is no historical record of supernovae to record the existence of such debris. Because Cassiopeia is an arched constellation that can be seen all year round in the middle and high latitudes of the northern hemisphere, this may be due to the absorption of interstellar dust, which makes visible light absorbed before reaching the earth. However, when john flamsteed made the catalog, he recorded that Cassiopeia 3 was a sixth-order dark star on August 6th, 1680 [5]. This view tends to explain that protostars are extremely massive and throw a lot of outer matter before explosion. These outer layers will mask the visible light released by the collapse of the protostar during the Big Bang.

Cassiopeia A is the first independent astronomical radio wave source discovered. It was discovered by astronomers martin ryle and Francis Graham Smith of Cambridge University in 1948 using a long Michelson interferometer. Its optical counterpart was confirmed as early as 1950 [7].