KIC 8462852[1] (also
Tabby's Star or
Boyajian's Star) is an
F-type main-sequence star located in the
constellation Cygnusapproximately 1,280 light-years (390 pc) from Earth.
Unusual light fluctuations of the star, including up to a 22% dimming in brightness, were discovered by
citizen scientists as part of the
Planet Hunters project, and, in September 2015, astronomers and citizen scientists associated with the project posted a
preprint of an article describing the data and possible interpretations.
The discovery was made from data collected by the
Kepler space telescope, which observes changes in the brightness of distant stars to
detect exoplanets.
Several hypotheses have been proposed to explain the star's large irregular changes in brightness as measured by its
light curve, but none to date fully explain all aspects of the curve. The likely explanation, announced by NASA on 4 October 2017, is that an "
uneven ring of dust" orbits KIC 8462852.
Another hypothesis, based on a lack of observed infrared light, posits a swarm of cold, dusty comet fragments in a highly eccentric orbit, however, the notion that disturbed comets from such a cloud could exist in high enough numbers to obscure 22% of the star's observed luminosity has been doubted.
Another hypothesis is that of a large number of small masses in "tight formation" orbiting the star.
Furthermore, spectroscopic study of the system has found no evidence for coalescing material or
hot close-in dust or
circumstellar matter from an evaporating or exploding planet within a few
astronomical units of the mature central star.
It has also been hypothesized that the changes in brightness could be signs of activity associated with intelligent extraterrestrial life constructing a Dyson swarm.
The scientists involved are very skeptical, however, with others describing it as implausible.
KIC 8462852 is not the only star that has large irregular dimmings, but all other such stars are
young stellar objects called YSO dippers, which have different dimming patterns. An example of such an object is
EPIC 204278916.
New light fluctuation events of KIC 8462852 began in the middle of May 2017, and totaled, as of 16 September 2017, four prominent dimmings, the last one being the largest of the year, with a 2.3% (or 3%) dimming.
On 10 October 2017, an increased brightening, lasting about two weeks, of the starlight from KIC 8462852 was noted, and a possible explanation described.
Around 20 November 2017, a fifth prominent dimming event began and had deepened to a 0.44% depth; as of 16 December 2017, the event recovered, leveled off for 11 days, faded again to a dimming depth of 1.25%, and began recovering again.
Dimming and brightening events of the star continue to be monitored, with related light curves released frequently.