Astronomers have found that the explosions of stars, known as supernovae, can leave behind gaseous remains that slam into hydrogen-rich gas and temporarily get bright again, appearing to remain luminous without any outside interference.
Assistant professor of physics and astronomy at Purdue University, Dan Milisavljevic, has been studying this phenomenon and believes this is what happens six years after star "SN 2012au" exploded.
"We haven't seen an explosion of this type, at such a late timescale, remain visible unless it had some kind of interaction with hydrogen gas left behind by the star prior to explosion," he said.
"But there's no spectral spike of hydrogen in the data - something else was energising this thing."
Milisavljevic believes this happens because, as large stars explode, their interiors collapse down to a point at which all their particles become neutrons. If the resulting neutron star has a magnetic field and rotates fast enough, it may develop into a pulsar wind nebula.
"We know that supernova explosions produce these types of rapidly rotating neutron stars, but we never saw direct evidence of it at this unique time frame," Milisavljevic explained.
"This a key moment when the pulsar wind nebula is bright enough to act like a lightbulb illuminating the explosion's outer ejecta."
This, according to a new report, is what likely happened to SN 2012au. Although the explosion wasn't bright enough to be termed a "superluminous" supernova, it was extremely energetic and long-lasting, and dimmed in a similarly slow light curve.
Milisavljevic predicts that if researchers continue to monitor the sites of extremely bright supernovae, they might see similar transformations.
"If there truly is a pulsar or magnetar wind nebula at the centre of the exploded star, it could push from the inside out and even accelerate the gas," he added.
"If we return to some of these events a few years later and take careful measurements, we might observe the oxygen-rich gas racing away from the explosion even faster."
To know for sure, we'll have to wait until the next generation of telescopes, which astronomers have dubbed "Extremely Large Telescopes," are developed, as they will have the ability to observe these events in such detail.
"This is a fundamental process in the universe. We wouldn't be here unless this was happening," Milisavljevic said.
"Many of the elements essential to life come from supernova explosions - calcium in our bones, oxygen we breathe, iron in our blood - I think it's crucial for us, as citizens of the universe, to understand this process."
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