Astronomers have observed in a galaxy relatively close to a star that is, to say the least, singular. Having survived his supernova explosion, he emerged from this cataclysmic event even brighter than before.
undead star
L’star in question, observed using the space telescope Hubbleis a woman blanche with a mass equivalent to that of the Sun, but whose size does not exceed that of the Earth. These incredibly dense objects turn out to be the cores of celestial bodies that have run out of fuel and have shed their outer layers. Scenario that should occur for our star in about 5 billion years.
As part of a binary system, the white dwarf has siphoned off and engulfed a good part of the matter of its companion star, thanks to its strong gravitational attraction. Reaching the 1.4 solar mass threshold resulted in a series of thermonuclear reactions in his heart, triggering a supernova who should have annihilated it.
“We were quite surprised to find that the star had survived and was shining brighter than before. “, Explain Curtis McCullylead author of the new study, published in The Astrophysical Journal. « During the explosion, radioactive materials were produced, explaining the luminosity of the supernova, but it turns out that some of it was retained by the surviving celestial fragment and used as fuel by the latter. »
This star ” zombie » is in a spiral galaxy called NGC 1309, significantly smaller than our Milky Way and located about 108 million light-years from Earth. A light year representing the distance traveled by a photon in a vacuum in 365.5 days, or 9,460.730 billion kilometers.
An Iax-type supernova
There are different types of supernovae, related to the size and composition of the star as well as the power of the explosion. star of the galaxy NGC 1309 offers researchers valuable insight into an event of ” type Iax ”, where the white dwarf undergoes an uncontrolled nuclear fusion after having seen its mass increase relatively quickly, but survives its supernova. Which is why they are called undead stars.
Although the researchers have detected around 50 such supernovae, they have so far been unable to identify the surviving stars. Like 97% of the stars in the Universe, the Sun is doomed to transform into a white dwarf but, in the absence of a companion star, cannot become a zombie star.