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Calcium-rich supernovae are a rare type of very fast supernova with unusually strong calcium lines in their spectra. [69] [70] Models suggest they occur when material is accreted from a helium-rich companion rather than a hydrogen-rich star. Because of helium lines in their spectra, they can resemble type Ib supernovae, but are thought to have ...
SN 1006 was a supernova that is likely the brightest observed stellar event in recorded history, reaching an estimated −7.5 visual magnitude, [3] and exceeding roughly sixteen times the brightness of Venus.
SN 1054 remnant (Crab Nebula)A supernova is an event in which a star destroys itself in an explosion which can briefly become as luminous as an entire galaxy.This list of supernovae of historical significance includes events that were observed prior to the development of photography, and individual events that have been the subject of a scientific paper that contributed to supernova theory.
Thus this category of supernovae has become highly useful as a standard candle for measuring cosmic distances. In 1998, the High-Z Supernova Search and the Supernova Cosmology Project discovered that the most distant Type Ia supernovae appeared dimmer than expected. This has provided evidence that the expansion of the universe may be accelerating.
— NASA Universe (@NASAUniverse) June 7, 2024. ... But while supernovas occur only once, a nova can happen again and again. After a nova explosion, the dwarf star remains intact, and the cycle ...
So a supernova with a measured redshift z = 0.5 implies the universe was 1 / 1 + 0.5 = 2 / 3 of its present size when the supernova exploded. In the case of accelerated expansion, a ¨ {\displaystyle {\ddot {a}}} is positive; therefore, a ˙ {\displaystyle {\dot {a}}} was smaller in the past than today.
Hypernovae are thought to be supernovae with ejecta having a kinetic energy larger than about 10 45 joule, an order of magnitude higher than a typical core collapse supernova. The ejected nickel masses are large and the ejection velocity up to 99% of the speed of light .
The supernova was about 21 million light-years from Earth and is expected to have left behind either a neutron star or black hole, based on current stellar evolution models. The supernova is located near a prominent HII region, NGC 5461, in an outer spiral arm of the bright galaxy. [3] By 22 May 2023, SN 2023ixf had brightened to about ...