The story began back in 2021, when the All-Sky Automated Survey for Supernovae (ASAS-SN) network noticed that a Sun-like star 1800 light years away was rapidly fading. Some 30 days later, NASA volunteer Arttu Sainio was reading X (formerly Twitter), and caught professional astronomers Dr. Matthew Kenworthy and Dr. Eric Mamajek speculating about this weird event. Arttu decided to further investigate this star, called Asassn-21qj, on his own, using data from NASA's NEOWISE mission. Arttu was surprised to find that the star had demonstrated an unexpected brightening in infrared light two years before the optical dimming event. So he joined the talk on social media and shared his finding with the two astronomers.
"Out of the blue, amateur astronomer Arttu Sainio on social media pointed out that the star brightened up in the infrared over a thousand days before the optical fading," said Kenworthy. "I knew then that this was an unusual event."
More contributions from amateurs helped determine the nature of the star. Amateur spectroscopist Hamish Barker tried to capture a spectrum of Asassn-21qj in late July, 2022. A spectrum spreads out the colors of the starlight, revealing the star's temperature.
However, the star turned out to be too dim, so Hamish asked Olivier Garde from a French amateur astronomy team if they could add ASASSN-21q to their target list. The team, called the Southern Spectroscopic project Observatory Team (or "2SPOT"), succeeded in collecting the needed spectrum in early September, 2022 and forwarded it Kenworthy. The 2SPOT team members are Stephane Charbonnel, Pascal Le Du, Olivier Garde, Lionel Mulato and Thomas Petit.
Two more amateur astronomers also independently observed the star and contributed their data to the study.
Amateur spectroscopist Sean Curry provided a spectrum of Asassn-21qj in early April, 2023. Dr. Franz-Josef (Josch) Hambsch followed the star from his remote observatory ROAD (Remote Observatory Atacama Desert). He submitted his results via the American Association of Variable Star Observers (AAVSO) database.
Want to help find more objects like Asassn-21qj? Help the Disk Detective project search for more exotic clouds of dust around nearby stars - or try the Backyard Worlds: Planet 9 project, where Sainio learned some of his skills. "Thanks to working previously with Backyard Worlds, retrieving WISE timeline photometry from NASA's infrared archive (IRSA) was a logical step for me," said Sainio.
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Related Links
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