Our galaxy is overdue a supernova we can see with the naked eye
On average a star in the Milky Way should explode every 61 years or so, yet the last one anyone actually saw here was Kepler's in 1604. Dust in the galactic disc may hide some; one explosion in the late nineteenth century went entirely unnoticed at the time.
A supernova is a star's final, cataclysmic blast, briefly rivalling a whole galaxy in brightness before fading over weeks or months. There are two main triggers. A white dwarf can reignite in runaway fusion, usually after stealing matter from a companion or merging with another star, and be blown apart completely. Or the core of a massive star, no longer able to hold itself up once it starts fusing iron, suddenly collapses into a neutron star or black hole. Only a tiny share of a galaxy's 100 billion or so stars can end this way.
The blast hurls several solar masses of debris at up to a few percent of light speed, sweeping up gas into an expanding remnant. That debris seeds space with elements from oxygen to rubidium, its shock waves can spark new stars, and supernovae are a major source of cosmic rays. Walter Baade and Fritz Zwicky began using the word, from the Latin nova, new, in 1931 lectures, and Knut Lundmark may have coined it on his own.
Human records reach far back. A Kashmiri rock carving dated to around 4500 BC may show one, though that cannot be verified. SN 1006 was described in China, Japan, Iraq, Egypt and Europe, and Chinese astronomers logged the 1054 blast that left the Crab Nebula. Tycho Brahe's star of 1572 and Kepler's of 1604 undermined the Aristotelian belief in an unchanging heaven. In 1987 SN 1987A erupted in the Large Magellanic Cloud and yielded the only astronomical neutrinos detected besides the Sun's.
Today amateurs and professionals catch about two thousand a year. Peak brightness makes them distance markers, and distant ones looking dimmer than expected in 2003 supported the idea that cosmic expansion is speeding up. In 2016 an Argentine amateur, Victor Buso, caught the first optical shock breakout, and the brightest on record, ASASSN-15lh, peaked at 570 billion Suns.
Source: Supernova
