Explosion Coming That Will Change the Night Sky

Calvin College professor Larry Molnar and his students along with colleagues from Apache Point Observatory (Karen Kinemuchi) and the University of Wyoming (Henry Kobulnicky) are predicting a change to the night sky that will be visible to the naked eye. 

This mesh shows the shape of the contact binary star system KIC 9832227 as the smaller star partially eclipses the larger one. For scale, the larger star has a radius 40 percent greater than our Sun. The orbital plane is tilted 53 degrees to the line of sight.

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.

The contact binary KIC 9832227 (red circles) is located in the constellation Cygnus, the Swan. Although astronomers aren’t sure how bright it will become if the stellar pair mergers, it could potentially rise to 2nd magnitude, easily naked eye.

Credit: L. Molnar / Calvin College

Chart shows the summer constellations of Cygnus and Lyra, with north up. The Northern Cross asterism is marked with the blue lines. The position of KIC 9832227 is shown with a red circle. It is in line with the three stars of the cross bar and, if it reaches 2nd magnitude in outburst, will be as bright as they are. Additionally, this chart shows a visualization of the swan Cygnus and of the lyre Lyra.

Contacts and sources:
Matt Kucinski, Lynn Rosendale
Calvin College

Link to preprint of scientific paper