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The explosions of stars, called supernovae, can be so bright that they eclipse their host galaxies. It takes months or years to disappear, and sometimes the gaseous remains of the explosion turn into hydrogen-rich gas and become temporarily bright again, but can they stay bright without outside interference?
That's what Dan Milisavljevic, assistant professor of physics and astronomy at Purdue University, believes to have seen six years after the explosion of "SN 2012au".
"We have not seen an explosion of this type, on such a late time scale, remaining visible unless there is an interaction with the hydrogen gas left by the star before the explosion," he said. "But there is no spectral peak of hydrogen in the data – something else was stimulating this thing."
As larger stars explode, their interiors collapse to a point where all their particles become neutrons. If the resulting neutron star has a magnetic field and rotates fairly rapidly, it can turn into a pulsar wind nebula.
That's probably what happened to SN 2012au, according to the results published in the Astrophysical Review Letters.
"We know that supernova explosions produce these types of rapidly rotating neutron stars, but we have never seen direct evidence at this unique moment," Milisavljevic said. "It's a key moment when the pulsar wind nebula is bright enough to act as a light bulb illuminating the outer ejectas of the explosion."
SN 2012au was already known to be extraordinary and strange in many ways. Although the explosion was not bright enough to be described as a "superluminous" supernova, it was extremely energetic and durable, and faded into an equally slow curve of light.
Milisavljevic predicts that if researchers continue to monitor extremely bright supernovae sites, they could see similar transformations.
"If there is really a pulsar or magnetar nebula in the center of the exploded star, it could push in and even accelerate the gas," he said. "If we go back to some of these events a few years later and take careful measures, we could observe the oxygen-rich gas that is moving away even faster from the explosion."
Superluminous supernovae are a hot topic in transient astronomy. They are potential sources of gravitational waves and black holes, and astronomers believe that they could be related to other types of explosions, such as gamma ray bursts and bursts. fast radio.
Researchers want to understand the fundamental physics that underlies them, but they are difficult to observe because they are relatively rare and arrive so far from the Earth.
Only the next generation of telescopes, which astronomers have dubbed "extremely large telescopes", will be able to observe these events in such detail.
"It's a fundamental process in the universe – we would not be here unless it happens," Milisavljevic said. "Many of the essentials for life come from supernova explosions – the calcium in our bones, the oxygen we breathe, the iron in our blood – I think it's crucial for us , citizens of the universe, to understand this process. "
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