Two Stars Are on a Crash Course and Will Explode as a Red Nova

Mark your calendars: In 2022, a rare "red nova" will appear in the sky, according to an unprecedented and ultra-precise stellar prediction.

If astronomer Larry Molnar is right, sometime around 2022 a spectacular explosion that occurred 1,800 years ago will burn bright as a new star in the constellation Cygnus, the world's first nova forecast.

Molnar, with Michigan's Calvin College, and his team have been monitoring a binary star system, called KIC9832227, which currently can only be seen with telescopes. The stars already are so close together, roughly three times the distance of Earth to the sun, that they basically share an atmosphere.

Based on the increasingly faster rate that the stars are spinning around each other, astronomers predict they are moving even closer together. Computer models show that the KIC9832227 pair will merge and explode in another five years or so, generating a bright and rare red nova that will be easily visible in Earth's night-time skies.

Actually, since KIC9832227 is located 1,800 light-years away, the crash already has happened, with light from the explosion racing outward at 186,000 miles per second every since, if Molnar's unprecedented prediction is right.

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Molnar and his team began a hunt for a so-called contact binary star after a 2008 Hubble image of a red nova. Archival data revealed telltale light curves of a binary star, which no longer exists today.

"We could see (in the archived data) that the period of the star was getting shorter over time. Shorter period means it's spiraling in, and it was getting shorter at an ever-accelerating rate. That's the Rosetta Stone I wanted to use to find the next one before it explodes," Molnar said at the American Astronomical Society meeting in Texas last week.

Enter KIC983227, which was among thousands of stars observed by NASA's Kepler Space Telescope. After hearing a presentation about the star, a student calculated its orbital period and then made the same calculation from archival data dating back to 1999. The numbers were different.

"He saw that the orbital period was getting shorter," Molnar said.

The team then used a small remotely operated telescope in New Mexico for two years of follow-on studies and found that KIC9832227's orbital period continued to shrink, meaning the stars were eclipsing one another at a faster and faster rate.

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The rate matched what was calculated for the binary star that proceeded Hubble's 2008 red nova discovery.

"This is not a model that has many degrees of freedom. It either fits or it doesn't and it did," Molnar said.

If the trend continues, the explosion should take place in 2022, give or take a year, and take about six months to reach peak brightness, roughly 10,000 times brighter than the original pair and easily visible to the unaided eye.

The nova will remain bright for several months, creating one more star in the crossbar of the Northern Cross.

"Anyone can see it," Molnar said. "You won't need a telescope to tell me in 2023 whether I was wrong or whether I was right."

Image: Light echoes from another rare red nova, V838 Monocerotis, was imaged by the Hubble Space Telescope in September 2006. The star actually exploded five years earlier, but light from the burst continued propagating outward through a cloud of dust surrounding the star. The light reflects or "echoes" off the dust and then travels to Earth. Credit: NASA/ESA/Hubble Heritage Team at STSci, AURA WATCH VIDEO: What Is a Supernova?