A Chinese-led team unravels the secrets of the giant star’s explosive death after support from citizen scientists

“Although the shock wave was expected to be very hot and short-lived, our study showed that this was not the case in the first hours when the star went supernova,” said the paper’s lead author Wang Xiaofeng of Tsinghua University in Beijing.

“This showed that the death of a massive star can be much more complicated than previously thought,” he said.

04:00 hours

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According to Wang, scientists have a relatively good match between theories and observations about how low- or intermediate-mass stars live and die. However, the mechanism of evolution of massive stars, which by definition have eight times the mass of the Sun or more, remains unclear.

When a star with about 18 solar masses was first discovered to have exploded by Japanese amateur astronomer Koichi Itagaki in May, it immediately became a treasure trove of observational data for scientists thanks to its extreme brightness and proximity to Earth.

As one of the most beautiful galaxies in the night sky, the Pinwheel Galaxy is constantly photographed by amateurs around the world. Wang collected images from both professional observatories and amateurs to reconstruct the entire explosion process.

His team contacted astronomy enthusiasts who had captured the galaxy before and after the supernova. The researchers then extract information for each color band, including red, green, and blue bands, and perform intensive calibration and comparison to obtain reliable multicolor photometric data.

To their surprise, the shock wave immediately after the explosion appeared to have a much lower temperature than expected.

“During the first few hours, the shock wave appeared red, which corresponds to several thousand degrees Celsius,” Wang said. Then it turned blue, or tens of thousands of degrees, as predicted by standard theory.

It was also observed that the shock wave lasted for several hours – much longer than the predicted duration of around 30 minutes.

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Wang said these observations provide direct evidence that the giant star ejected a significant amount of gas and dust to form a dense medium that eventually absorbed much of the shock wave’s energy.

Meanwhile, the dust layers are likely asymmetric, leading to the wave’s long journey from the core to outer space, he added.

“Our work would not have been possible without the help of amateur astronomers in and outside of China,” he said. “I really hope that such collaborations happen more often and even open a new paradigm in astrophysical research in the future.”

Elliott Herman, professor emeritus of plant biology at the University of Arizona in the US, was one of the amateur astronomers contacted by Wang’s team.

Herrmann said he happened to notice the supernova warning and stayed up much of the night to take images using a remote network of telescopes in Utah as the supernova grew brighter and brighter.

When asked to share the original data set with Wang’s group, Herman happily agreed. His data and that of other amateurs were combined, leading to the analyzes and conclusions described in the Nature paper.

Compared to professional observatories, which often operate based on schedules, amateurs have more flexibility, Herman said.

“Amateurs can change their minds and go on the lookout for new objects of interest,” he said.

02:11 a.m

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Last seen by Neanderthals: The “Green Comet” observed by astronomers in Greece

Astronomy is a unique discipline in which amateurs play a significant role, Herman said. Historically, science was mostly done by amateurs and academics funded by wealthy people before it became government funded.

Today, there is no other major discipline like astronomy.

“I was a program manager at the National Science Foundation (in biology) at one time, and I’ve never seen a grant or project with amateur participation,” he said.

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Astronomy welcomes amateurs, including people from all walks of life who enjoy searching for the wonders of the universe.

“This synergy is science at its best. I am so excited to be involved in this project and its publication,” Herman said.

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