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takyon writes:

Astronomers at Calvin College in Michigan have predicted that the contact binary star system KIC 9832227 will merge and produce a "red nova" around 2022 (2022.2 ± 0.6):

Molnar's exploration into the star known as KIC 9832227 began back in 2013. He was attending an astronomy conference when fellow astronomer Karen Kinemuchi presented her study of the brightness changes of the star, which concluded with a question: Is it pulsing or is it a binary?

Also present at the conference was then Calvin College student Daniel Van Noord '14, Molnar's research assistant. He took the question as a personal challenge and made some observations of the star with the Calvin observatory. "He looked at how the color of the star correlated with brightness and determined it was definitely a binary," said Molnar. "In fact, he discovered it was actually a contact binary, in which the two stars share a common atmosphere, like two peanuts sharing a single shell. From there Dan determined a precise orbital period from Kinemuchi's Kepler satellite data (just under 11 hours) and was surprised to discover that the period was slightly less than that shown by earlier data" Molnar continued.

This result brought to mind work published by astronomer Romuald Tylenda, who had studied the observational archives to see how another star (V1309 Scorpii) had behaved before it exploded unexpectedly in 2008 and produced a red nova (a type of stellar explosion only recently recognized as distinct from other types). The pre-explosion record showed a contact binary with an orbital period decreasing at an accelerating rate. For Molnar, this pattern of orbital change was a "Rosetta stone" for interpreting the new data.

Upon observing the period change to continue through 2013 and 2014, Molnar presented orbital timing spanning 15 years at the January 2015 meeting of the American Astronomical Society, making the prediction that KIC 9832227 may be following in the footsteps of V1309 Scorpii. Before taking the hypothesis too seriously, though, one needed to rule out other, more mundane, interpretations of the period change. In the two years since that meeting, Molnar and his team have performed two strong observational tests of the alternative interpretations. First, spectroscopic observations ruled out the presence of a companion star with an orbital period greater than 15 years. Second, the rate of orbital period decrease of the past two years followed the prediction made in 2015 and now exceeds that shown by other contact binaries.

The prediction has been refined from an earlier estimate of 2018 to 2020. Illustrations.

PREDICTION OF A RED NOVA OUTBURST IN KIC 9832227

Related: KIC 9832227: a red nova precursor
Evolution of the stellar-merger red nova V1309 Scorpii: SED analysis

Original Submission