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Amateur Astronomers Help Discover Cosmic Crash

Heavily pixelated video showing movement around a black circular object in the center of the frame.
NASA Volunteer Arttu Sainio saw the star Asassn-21qj brightening, possibly due to crashing planets.
Credit: Dan Caselden, NASA

Astronomers found what looks like a glowing cloud of dust from a massive planetary pile-up—and NASA volunteers helped make the discovery! A recent paper in Nature describes how an international group of professional and amateur astronomers teamed up to measure the heat glow of two ice giant planets colliding and see the resultant dust cloud moving in front of the parent star several years later.

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 Stéphane Charbonnel, Pascal Le Dû, 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.

Congratulations to all the researchers who collaborated on this study!



Last Updated
Dec 18, 2023
NASA Science Editorial Team