It’s not an asteroid on a beeline to our little Blue Dot. Or, some rogue black hole ready to swallow us. Nope, this prediction is a lot cooler and a lot less dangerous for us. A Calvin College professor (and several colleagues) believes a binary star he’s been studying is on the cusp of merging and exploding. If the prediction pans out, a binary star you can’t even see with the naked eye will surge in brightness and temporarily become one of the brightest stars in the sky in 2022.
Calvin College professor Larry Molnar’s prediction started in 2013. While attending an astronomy conference, he saw a presentation from another astronomer, Karen Kinemuchi, about the brightness changes in a star known as KIC 9832227. Was the star pulsing, or was there another star lurking close by?
Molnar’s research assistant Daniel Van Noord also attended the conference and wanted to know exactly what was going on with KIC 9832227.
“He looked at how the color of the star correlated with brightness and determined it was definitely a binary,” said Molnar in a Calvin College news release. But it wasn’t a regular pair of stars in close proximity. “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,” Molnar added.
A contact binary hints a merger and explosion could happen soon, but how did Molnar and his astronomers get to 2022? Noord used Kinemuchi’s Kepler satellite data of the star to come up with a precise orbital period. It was just under 11 hours. Which surprised them as it was slightly less than what earlier data showed. A decreasing orbital period points to the binary star getting closer and closer.
This has been seen before. The star V1309 Scorpii surprised astronomers when it exploded in 2008. Astronomer Romuald Tylenda poured over observational archives to see how the star behaved leading up to the explosion. Can you guess what Tylenda found? Yep, a contact binary with a decreasing orbital period.
Molnar and his colleagues didn’t make the prediction without checking for other possible interpretations of their data. First, they ruled out a companion star with an orbital period greater than 15 years. Then they looked at the orbital period again with a Calvin College telescope over the past two years. The orbital period is continuing to decrease.
“Bottom line is we really think our merging star hypothesis should be taken seriously right now and we should be using the next few years to study this intensely so that if it does blow up we will know what led to that explosion,” said Molnar.
If the prediction comes true, a new star will be visible to the naked eye in the constellation Cygnus. If it doesn’t, astronomers can learn why. It’s a win-win for science.
And you can watch it unfold too. “The orbital timing can be checked by amateur astronomers,” said Molnar. “It’s amazing the equipment amateur astronomers have these days. They can measure the brightness variations with time of this 12th magnitude star as it eclipses and see for themselves if it is continuing on the schedule we are predicting or not.”
Top image credit: Space Telescope Science Institute