This is probably the most comprehensive science of supernovae.

Supernova is very bright, and its radiant energy is equivalent to the energy emitted by the whole life cycle of the sun. As early as A.D. 185, Chinese astronomers recorded the observation of supernovae. According to the absorption lines of different chemical elements in their spectra, they are divided into five categories. Supernovae also promoted the evolution of stars.

Supernovae are very shiny. The radiation it emits usually illuminates the whole galaxy briefly, and then disappears from people's sight within weeks or months.

In the short life of a supernova, the energy it radiates is equivalent to the sum of the energy expected to be released by the sun in the whole life cycle. An explosion of this scale can throw a large amount (or all) of stellar matter at a speed of 30,000 kilometers per second (10% of the speed of light), causing shock waves to enter the surrounding interstellar medium. The shell-like structure formed by the expansion of gas and dust caused by shock wave is called supernova remnant.

Illustration: Multi-wavelength X-ray, infrared and optical compiled images of Kepler supernova remnant SN 1604.

There are several types of supernovae. Type I and type II may be formed in two ways: stopping or suddenly starting to generate energy through nuclear fusion. When the old heavyweight stars gradually stop producing energy from nuclear fusion, gravitational collapse may occur. These stars eventually become neutron stars or black holes, and release gravitational potential energy to heat and peel off the outer layers of the stars. Another possibility is that the white dwarf has accumulated enough matter from its companion star (through accretion or merger) to make its core reach a temperature that can ignite carbon fusion. At the same time, out-of-control nuclear fusion also devoured the white dwarf, ending its life. When the mass of a star is greater than the Chandraseka limit (about 1.38 times the mass of the sun), it will lead to the "extinction" (that is, collapse) of the star core, and the white dwarf star formed by accretion will also start to spontaneously ignite when it approaches this limit. The poor white dwarf will suffer a completely different thermonuclear explosion, much smaller than nuclear fusion. This explosion is caused by hydrogen accumulated on the surface of white dwarfs, and the light generated by the explosion is often mistaken for a newly generated star. Therefore, scientists call this explosion a "new star". And those lone stars whose mass is less than 9 suns, such as the sun itself, will eventually only evolve into white dwarfs (not supernovae).

Illustration: Type Ia supernovae will appear when white dwarfs absorb companion matter, exceed Chandraseka limit and explode.

Although supernovae have never been observed in the Milky Way since 1964, supernovae occur once every 50 years on average in galaxies the size of the Milky Way. They have made important contributions to the enrichment of interstellar media containing elements with greater mass. In addition, the expansion shock wave generated by supernova explosion will also promote the formation of new stars.

Supernova is "supernova" in English. In Latin, "nova" (plural novae) means "new", which means a very bright nova is shining in the sky. The prefix "super-" distinguishes supernovae from ordinary nova. (The brightness of ordinary nova will also increase continuously, although the increase is smaller than that of supernova, and it is caused by different mechanisms. The word supernova was named by Swiss astrophysicist and astronomer Fritz Wei Zi, and was first used in writing materials in 1926.

The earliest recorded supernova was Sn 185 observed by Chinese astronomers in 1985. The brightest record in supernovae was obtained by SN 1006. China and Islamic astronomers have described this supernova in detail. The much-talked-about supernova SN 1054 eventually became the Crab Nebula.

Illustration: Crab Nebula

Source: Sohu.com.

The latest supernovae SN 1572 and SN 1604 observed by naked eyes in the Milky Way have made great contributions to the development of European astronomy, because their appearance refutes Aristotle's view that the universe except the moon and planets cannot be changed.

The discovery of supernovae will be reported to the central astronomical telegraph office of the International Astronomical Union, and then the central astronomical telegraph office will issue a naming statement. The name of a supernova usually consists of the year when it was discovered plus one or two designated letters. The first 26 supernovae discovered in a year will be named by capital letters "A" to "Z", followed by pairs of lowercase letters, such as "aa" and "ab".

Supernovae recorded in history can only be known when they appeared, such as SN 185, SN 1006, SN 1054, SN 1572 (Andromeda) and SN 1604 (Kepler). Since 1885, even if only one supernova is found in a year, letter symbols (such as SN 1885A, SN 1907A, etc.) have been used all the time. ), and only one supernova, SN 1947A, was discovered within one year. Before 1987, two letters were rarely used in the naming of supernovae, but since 1988, two letters have been frequently used.

Illustration: SN 1987A photographed by Hubble is located in the middle of large magellanic cloud.

In the process of exploring supernovae, scientists classified different chemical elements according to absorption lines. The first criterion is to judge whether the absorption line caused by hydrogen is generated. If the spectrum of a supernova contains a hydrogen absorption line (Balmer line system in the visible part of the spectrum), it is classified as type II, and the rest as type I. In these two categories, it will be subdivided according to the existence of absorption lines of other elements and the shape of the light curve (the functional image of supernova apparent magnitude changing with time).

Illustration: Optical curve of SN 1987A

Source: ARAA

Supernova remains are composed of dense celestial bodies and shock waves containing rapidly expanding substances. After two centuries of free expansion, this mass will enter the adiabatic expansion period, during which it will be cooled and mixed with the surrounding interstellar medium for about 654.38+0 million years.

Illustration: BIGBANG structure diagram

Source: Li Li Li.

The Big Bang produced hydrogen, helium and trace lithium. All the heavier elements were synthesized in stars and supernovae. Supernovae tend to enrich the surrounding interstellar medium with metal elements (non-hydrogen helium elements). These injected elements eventually become a member of the molecular cloud that can form stars. Due to the compression of dense molecular clouds in nearby space, the kinetic energy generated by the expansion of supernova remnants can promote the formation of stars.

Author: Tim trotter

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