(CN) --- Researchers revealed on Monday evidence of an entirely new type of supernova that, despite being long theorized to exist somewhere in the cosmos, has never been directly observed until now.
In a nearby galaxy some 31 million light years away sits a supernova --- a bright and incredibly powerful stellar explosion --- that left scientists quite stumped. Dubbed SN 2018zd and discovered using dozens of telescopes from around the world, this supernova defied all known expectations of what to expect from a typical supernova and displayed a combination of characteristics scientists had never seen before.
What at first struck experts as a mystery, however, turned out to be a shocking discovery. Upon closer inspection of the peculiar object, scientists found they actually discovered a brand new type of supernova that has been long theorized but never proven --- the electron-capture supernova.
"We started by asking 'What's this weirdo?'” said Daichi Hiramatsu, a graduate student at the University of California, Santa Barbara and Las Cumbres Observatory. "Then we examined every aspect of SN 2018zd and realized that all of them can be explained in the electron-capture scenario."
In a study published Monday in the journal Nature Astronomy, a team of international researchers revealed why this discovery could completely change the game in how we view supernovas.
This is largely due to the fact that, historically, supernovas fall into one of two distinct types: a thermonuclear supernova and an iron core-collapse supernova. A thermonuclear supernova happens when the remnants of a dead star known as white dwarf explodes after gaining too much matter, while an iron core-collapse supernova occurs when --- as its name implies --- the iron core of a sizeable star collapses in on itself due to a lose of nuclear fuel.
But for decades, researchers believed that a third type of supernova could exist somewhere in the expanse of space. One that struck a balance between the two types we knew of, in which a star was too light to be capable of prolonging its life, too small to create an iron core and too heavy to escape the inevitability of its own collapse.
Now researchers believe they have found that third type of supernova in SN 2018zd. While researchers found some other supernovas in the universe that had some oddball qualities, only SN 2018zd carried all of the six required characteristics --- things like a neutron-rich core and an odd chemical makeup --- to be considered an electron-capture supernova.
Ken'ichi Nomoto of the University of Tokyo was one of the first ones nearly four decades ago to suggest that these types of objects existed, and is thrilled that his long-sought supernova has finally been found.
"I am very pleased that the electron-capture supernova was finally discovered, which my colleagues and I predicted to exist and have a connection to the Crab Nebula 40 years ago,” Nomoto said. “I very much appreciate the great efforts involved in obtaining these observations. This is a wonderful case of the combination of observations and theory."
What’s more is that researchers believe that these findings could help shed some light on one of the most famous supernovas in history.
Nearly a thousand years ago in 1054 A.D., ancient historical records from China and Japan tell of a great supernova explosion that happened in our very own galaxy. It was apparently so bright that it could be seen in broad daylight for nearly a month, and could be glimpsed in the night sky for up to two years.
Scientists have long labored to learn more about this ancient cosmic event and its resulting remnant, the Crab Nebula, and armed with Monday’s revelations experts are fairly confident this explosion was an electron-capture supernova.
“The term Rosetta Stone is used too often as an analogy when we find a new astrophysical object but in this case I think it is fitting,” Andrew Howell, a staff scientist at Las Cumbres Observatory and adjunct faculty at UCSB, said. “This supernova is literally helping us decode thousand-year-old records from cultures all over the world.”
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