December 1, 2015
A team of astronomers suggests a swarm of comets blocked the light from the star named KIC 8462852 in 2011 and 2013, after ruling out planetary impact and asteroids as possible causes.
While searching for planets in other star systems - exoplanets - NASA’s Kepler telescope observed two unusual events concerning star designated KIC 8462852. On two separate occasions, in 2011 and 2013, star’s light dimmed in a way that drew attention from scientific community.
Kepler finds exoplanets by measuring regular dips in stars’ luminosity, but the irregular nature of the two events ruled out an exoplanet as a cause. Other likely candidates were fragments of planets, asteroids and comets. Fragments of planets after a planetary impact or asteroids colliding with each other would both leave a clue in form of excess infrared light around, and not just in front of, KIC 8462852.
First thing scientist did was check the data from NASA's Wide-Field Infrared Survey Explorer (WISE) space telescope and found no traces of infrared light. However, since WISE observed the star in 2010 before the two events in question, it was possible that no collisions between asteroids or planetary impacts had yet occurred.
So, they turned to Spitzer Space Telescope that observed KIC 8462852 in 2015. Massimo Marengo of Iowa State University, Ames, USA, and his team couldn’t find any infrared light around the star using data from Spitzer either, so they think the comets are the most likely cause for two events.
They suggest that the first time the light from KIC 8462852 was blocked, a very large comet passed in front of the star. Two years later, many smaller comets, led by the large one that passed two years earlier, could have blocked the light again. Since they are cold bodies, comets don’t leave infrared trace for Spitzer to be detected in 2015.
"This is a very strange star," Marengo said. "It reminds me of when we first discovered pulsars. They were emitting odd signals nobody had ever seen before, and the first one discovered was named LGM-1 after 'Little Green Men.' We may not know yet what's going on around this star, but that's what makes it so interesting."
Depending on how long it takes for comets to orbit KIC 8462852, further observations could confirm the team’s theory. Team’s research is accepted for publication in the Astrophysical Journal Letters.