The mysterious light patterns behind the bizarre star KIC 8462852 may have been solved, and there's no alien megastructure involved.
An alien megastar deep in space has baffled scientists with its mysterious light patterns that caused some to posit an alien civilization, but not any more: scientists think they have an explanation. Instead of being the sign of a far-away alien megastructure, the strange dipping and dimming of light surrounding the star KIC 84622852 indicates that it ate a planet about 10,000 years ago.
The star, also known as Tabby’s Star, had mystified scientists for the past 18 months. It had been discovered in 2009, but it was these strange light patterns that really had astronomers scratching their head.
The study, published in the Monthly Notices of the Royal Astronomical Society, claims that if KIC 8462852 gobbled up one of its own planets, it would have created light patterns that were similar to what has so far been observed.
While the alien megastructure claim hadn’t really been taken too seriously in the scientific community, scientists weren’t sure to make of it. Some suggested that a large number of comets were orbiting the star, causing the erratic shifts in light, or that the star was so active that it periodically emitted light at tremendous energies.
The abstract and intro to the paper follow below.
The Kepler-field star KIC 8462852, an otherwise apparently ordinary F3 main-sequence star, showed several highly unusual dimming events of variable depth and duration. Adding to the mystery was the discovery that KIC 8462852 faded by 14% from 1890 to 1989 (Schaefer 2016), as well as by another 3% over the 4 year Kepler mission (Montet & Simon 2016). Following an initial suggestion by Wright & Sigurdsson, we propose that the secular dimming behavior is the result of the inspiral of a planetary body or bodies into KIC 8462852, which took place ∼ 10−104 years ago (depending on the planet mass).
Gravitational energy released as the body inspirals into the outer layers of the star caused a temporary and unobserved brightening, from which the stellar flux is now returning to the quiescent state. The transient dimming events could then be due to obscuration by planetary debris from an earlier partial disruption of the same inspiraling bodies, or due to evaporation and out-gassing from a tidally detached moon system. alternatively, the dimming events could arise from a large number of bodies comet- or planetesimal-mass bodies placed onto high eccentricity orbits by the same mechanism (e.g. Lidov-Kozai oscillations due to the outer M-dwarf companion) responsible for driving the more massive planets into KIC 8462852.
The required high occurrence rate of KIC 8462852-like systems which have undergone recent major planet inspiral event(s) is the greatest challenge to the model, placing large lower limits on the mass of planetary systems surrounding F stars and/or requiring an unlikely coincidence to catch KIC 8462852 in its current state.
The Kepler-field star KIC 8462852, an otherwise apparently ordinary F3 main-sequence star with a Gaia-measured parallax distance of about 400 pc (Hippke & Angerhausen 2016), was discovered by the Planet Hunters team to exhibit highly peculiar and unique photometric features (Boyajian et al. 2016). Over the 4 year period of the nominal Kepler mission (Borucki et al. 2010), the star underwent several dimming events of variable depth and duration, ranging from approximately 0.5 − 20% reduction in the total stellar flux. These events are often asymmetric in shape, displaying an apparent lack of periodicity and repeatability. Groups of clustered dips were observed, centered around days 800 and 1500 (‘D800’ and ‘D1500’, respectively), but smaller dips are detected at other phases over the observing period.