A star that never dies. An international team of astronomers including experts Nick Konidaris and Benjamin Shappee of Carnegie Mellon University (USA) has discovered a star that exploded several times over a period of 50 years without disappearing in these events. The finding, published by Nature, completely confuses our existing knowledge about the end of a star’s life through a supernova.
Usually, when a star becomes a supernova, that’s it. Is the end. However, this new discovery could change the way we see the death of the stars because this one in particular, called iPTF14hls, became a supernova; then, it became illuminated again and, about 60 years later, it became a supernova again. How is it possible?
At first it was classified as a type II-P supernova, it looked like any other known supernova. In fact, the spectroscopic characteristics of the supernova iPTF14hls were identical to those of a type II supernova -P. But, to the surprise of the astronomers, several months later, he did something that supernovas do not usually do: he shone again.
After 600 days of observation, it dimmed and lit several times, at least five times in less than three years. In general, supernovas reach their maximum brightness, shine for a few months and then darken continuously.
When the scientists re-examined the archival data, they found something surprising: the star had already exploded in type II-P supernova in 1954.
“This supernova breaks with everything we thought we knew about how supernovae work,” says Iair Arcavi of the Las Cumbres Observatory and leader of the work. “It’s the biggest puzzle I’ve found in nearly a decade of studying stellar explosions.
“According to the data published in the journal Nature, the original star was large, at least 50 times more massive than the Sun, and probably much larger.” The iPTF14hls supernova may be the most massive stellar explosion ever seen,” says co-author Lars Bildsten.
A possible explanation to the enigma
Researchers believe that it is an unstable supernova pulse, something that had never been observed before, so it would be the first phenomenon of this type in the history of astronomy, something that is believed to have happened to the star Eta Carinae A in 1843. But it is only a hypothesis.
This event seems to be a supernova that does not destroy its host star, and generally occurs in stars with around 95 to 130 solar masses. The supernovas would continue to be produced until the star finally collapsed into a black hole.
“These events should be common at the beginning of the universe, but not today, it’s almost like finding a living dinosaur today, if it happens to you, it’s normal to ask yourself if it’s really a dinosaur,” says Andy Howell, co-author of study.
However, there is a problem with that hypothesis. The unstable supernova pulsation model does not take into account the continuous presence of hydrogen. iPTF14hls retained too much hydrogen to adjust to a pulse. In addition, the star’s most recent explosion used more energy than this model can represent. Which means that either iPTF14hls is a supernova of this type but really strange, or something completely new.
The team continues to monitor the supernova with the hope that the response will eventually clear up.