Astronomers announce that they have isolated the remains of an absolutely colossal supernova less than 4,000 light years from Earth. In terms of apparent size, imagine an expanding cloud of gas and dust nearly a hundred times larger than the full Moon.
A supernova is a dying star. Two main mechanisms can produce this type of event. The first results from the thermonuclear explosion of a dead star called a white dwarf initiated by the capture of material dumped by a close companion (thermonuclear supernova). This process therefore involves two objects contained in a binary system. The second results from the implosion of a massive star. This is called a core-collapse supernova).
Either way, the result is the same:a cataclysmic explosion releasing an expanding shell of the star's outer material which, for a time, may shine brighter than an entire galaxy .
Note that these events play a major role in the evolution of the cosmos. It is indeed during these explosions that the heaviest elements that sow the universe are formed.
A team of astronomers led by Werner Becker, from the Max Planck Institute in Germany, announces that they have isolated the remains of one of these stellar explosions . Called Hoinga, after the medieval name of his hometown, it is the largest supernova remnant ever discovered.
"In terms of apparent size, imagine an expanding cloud of dust and gas approximately 90 times larger than the full Moon “, emphasizes the researcher.
So how come we've been missing out all this time? In reality, these remains are only visible in X-rays and only under the eye of one of the most powerful X-ray telescopes built to date:eROSITA. Launched in 2019, you will find it on board the Russian-German SRG satellite.
“The eROSITA telescope is twenty-five times more sensitive than its predecessor ROSAT. Also, we expected to discover new supernova remnants in the coming years, but we were pleasantly surprised to see one so quickly “, said astronomer Natasha Hurley-Walker, of the International Center for Research in Radio Astronomy in Australia.
Based on this radio data, the team calculated that these remains are between 21,000 and 150,000 years old . In addition, they evolve relatively close to the Earth, between 1470 and 3915 light years away .
The location of this supernova is also surprising. These remnants were indeed isolated far from the galactic plane where most Milky Way stars (and therefore supernova remnants) reside. After analyzing past data, available on the arXiv server, it also appeared that this supernova was already present (weakly, but present) in the ROSAT telescope data taken thirty years ago.
"Supernova remnants are not generally expected to be found at high galactic latitudes, so these areas are generally not the focus of investigations, which means there may be even more of these overlooked remains waiting to be discovered “, notes Werner Becker.
