Obi-Wan Kenobi in his force ghost form | Credit: Courtesy

Normally, when a star goes supernova, the thermonuclear explosion blows it utterly apart, leaving nothing behind. An astronomer with Las Cumbres Observatory announced this week, however, that he observed a supernova named SN 2012Z in the nearby spiral galaxy NGC 1309 that had not only survived the explosion but grew larger and brighter as a result. 

“I was stunned,” said Dr. Curtis McCully of the discovery, which was the subject of a Wednesday press conference and a newly published article in The Astrophysical Journal. “My immediate reaction was that I did something wrong.” But a re-analysis of the data revealed McCully’s eyes weren’t deceiving him and SN 2012Z had in fact cheated death.

His new observations confirmed what had only been a working theory. SN 2012Z turned out to be a rare type of supernova, referred to as a Type Iax supernova, that are the dimmer, weaker cousins of the more traditional Type Ia supernova and are the result of a failed Type Ia explosion. McCully and his team believe the half-exploded star got brighter because it puffed up to a much larger size. Over time, they expect it to slowly return to its initial state, only less massive.

Scientists still aren’t exactly sure what makes a star ― specifically white dwarfs, which are roughly the mass of the sun packed into the size of the Earth ― erupt into supernovas. One theory is that the dwarf steals matter from a companion star and when it gets too heavy, thermonuclear reactions ignite in the core and lead to a runaway explosion.

“This star surviving is a little like Obi-Wan Kenobi coming back as a Force ghost in Star Wars,” said Dr. Andy Howell, another author on the study and a staff scientist at Las Cumbres Observatory. “Nature tried to strike this star down, but it came back more powerful than we could have imagined.”

Color images of NGC 1309 both before and after SN 2012Z. The left panel shows the Hubble Heritage (pre-explosion) image of NGC 1309. The top-middle panel shows a zoom in on the position of the supernova from the pre-explosion image. The top-right shows SN~2012Z from the 2013 visit. The middle-bottom panel shows the location of SN~2012Z in the latest observations in 2016. The bottom-right panel shows the difference image between the pre-explosion images and the observations from 2016. The source at the location of SN~2012Z is still significantly brighter in 2016 than in the pre-explosion images. | Credit: McCully et al. 2022, ApJ, 925, 138.

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