In the night sky that we can observe with the naked eye, the supernova explosion is a very peculiar phenomenon, which is manifested as a very bright star suddenly appearing somewhere, and the beginning of a period of time will be very bright, usually up to three months or even three years long, in the process will gradually darken and eventually disappear, in ancient times, this sudden appearance of the big star is called "guest star".
Ancient more famous supernovae are "TianguanKe Star" and "Tycho Supernova", Tianguan Kexing is a supernova seen in 1054 during the Northern Song Dynasty in China, it is the predecessor of today's Crab Nebula, about 6500 light-years away from us, recorded by astrologers of China's Song Dynasty.
Tycho supernova is a supernova that erupted in the constellation Cassiopeia in 1572, recorded in detail by the Danish astronomer Tycho, and Chinese astronomers have also recorded it, this supernova is a la-type supernova explosion, and its shell gas is still erupting outward from the center at a speed of about 9,000 kilometers per second.
The phenomenon of supernova explosions has been recorded more than 10 times in China's historical records. Recently, the astronomical research team at the University of Göttingen in Germany for the first time found a nova remnant at the center of the Messier 22 globular cluster, which can be determined to be a pulsar from its characteristics, and the analysis believes that the location and brightness of this supernova remnant are consistent with an ancient observation record by Chinese astronomers in 48 BC.
The Han Dynasty historical book "Book of Han" once recorded that in April of the first year of the Han Yuan Emperor (48 BC), there were guest stars as big as melons, blue and white, and the second star in the Nandou, the east can be four feet...
From 48 BC to the present 2067, the supernova remnants have now formed a red shining nebula composed of hydrogen and other gases, with a diameter of 1.2 trillion kilometers, about 8,000 times the distance between the Earth and the Sun (the distance between the sun and the earth), which is much larger than the volume of the largest star shield uy that we often say, that is, the volume of the black hole in the center of the m87 galaxy released some time ago is also far from it.
However, although this nebula is large, its mass is very small, even less than the mass of a sun, because the nebula is mostly very thin, and it will become thinner as the volume expands.
Ancient records of supernovae and comets can be deduced in the position and time of some stars found by modern astronomical observations, and their traces can be found in ancient records, because the speed of expansion of the nebula after the supernova explosion can also be converted into a shrinking rate, when it shrinks to a star, it is the time of its eruption; and comets are periodic, and through the periodicity of their orbital time, it can be calculated at what time it passes near the Earth.