Originally, and until Kohler's work of 2017, it was thought that, based on the
spectrum and stellar type of Tabby's Star, its changes in brightness could not be attributed to
intrinsic variability. Some of the proposed explanations involve
interstellar dust, a series of giant planets with very large ring structures, a recently captured
asteroid field, and an artificial
megastructure orbiting the star. However, in September 2019, astronomers reported that the observed dimmings of Tabby's Star may have been produced by fragments resulting from the
disruption of an
orphaned exomoon.
Circumstellar dust ring " orbiting Tabby's Star Based on these studies, on 4 October 2017, NASA reported that the unusual dimming events of Tabby's Star are due to an "uneven ring of
dust" orbiting the star. A related, but more sophisticated, explanation of dimming events, involving a transiting "
brown dwarf" in a 1600-day eccentric orbit near Tabby's Star, a "drop feature" in dimness, and predicted intervals of "brightening", has been proposed. Dimming and brightening events of Tabby's Star continue to be monitored; related light curves are updated and released frequently. Nonetheless, data similar to that observed for Tabby's Star, along with supporting data from the
Chandra X-ray Observatory, were found with dust debris orbiting
WD 1145+017, a
white dwarf that also has unusual light curve fluctuations. Further, the highly variable star
RZ Piscium, which brightens and dims erratically, has been found to emit excessive
infrared radiation, suggesting that the star is surrounded by large amounts of gas and dust, possibly resulting from the
destruction of local planets.
A cloud of disintegrating comets One proposed explanation for the reduction in light is that it is due to a cloud of disintegrating
comets orbiting the star elliptically. This scenario would assume that a planetary system around Tabby's Star has something similar to the
Oort cloud and that gravity from a nearby star caused comets from said cloud to fall closer into the system, thereby obstructing the spectra of Tabby's Star. Evidence supporting this hypothesis includes an M-type
red dwarf within of Tabby's Star.
Younger star with coalescing material around it Astronomer Jason T. Wright and others who have studied Tabby's Star have suggested that if the star is younger than its position and speed would suggest, then it may still have coalescing material around it. A
0.8–4.2-micrometer spectroscopic study of the system using the
NASA Infrared Telescope Facility (NASA IRTF) found no evidence for coalescing material within a few
astronomical units of the mature central star. A massive collision scenario would create warm dust that glows in
infrared wavelengths, but there is no observed excess infrared energy, ruling out massive planetary collision debris.
Consumption of a planet In December 2016, a team of researchers proposed that Tabby's Star swallowed a planet, causing a temporary and unobserved increase in brightness due to the release of gravitational energy. As the planet fell into its star, it could have been ripped apart or had its moons stripped away, leaving clouds of debris orbiting the star in eccentric orbits. Planetary debris still in orbit around the star would then explain its observed drops in intensity. Additionally, the researchers suggest that the consumed planet could have caused the star to increase in brightness up to 10,000 years ago, and its stellar flux is now returning to the normal state.
Large planet with oscillating rings Sucerquia et al. (2017) suggested that a large planet with oscillating rings may help explain the unusual dimmings associated with Tabby's Star.
Large ringed planet followed by Trojan swarms Ballesteros et al. (2017) proposed a large, ringed planet trailed by a swarm of
Trojan asteroids in its L5
Lagrangian point, and estimated an orbit that predicts another event in early 2021 due to the leading Trojans followed by another transit of the hypothetical planet in 2023. The model suggests a planet with a radius of 4.7
Jupiter radii, large for a planet (unless very young). An early
red dwarf of about would be easily seen in
infrared. The current radial velocity observations available (four runs at σ
v ≈ 400 m/s) hardly constrain the model, but new radial velocity measurements would greatly reduce the uncertainty. The model predicts a discrete and short-lived event for the May 2017 dimming episode, corresponding to the
secondary eclipse of the planet passing behind KIC 8246852, with about a 3% decrease in the stellar flux with a transit time of about 2 days. If this is the cause of the May 2017 event, the planet's orbital period is more precisely estimated as 12.41 years with a
semi-major axis of 5.9 AU. -->
Intrinsic luminosity variations The reddening observed during the deep dimming events of Tabby's Star is consistent with cooling of its photosphere. It does not require obscuration by dust. Such cooling could be produced by a decreased efficiency of heat transport caused e.g. by decreased effectiveness of convection due to the star's strong differential rotation, or by changes in its modes of heat transport if it is near the transition between radiative and convective heat transport. The "missing" heat flux is stored as a small increase of internal and potential energy. "Avalanche statistics" with a
self-similar or
power-law spectrum are a
universal property of
complex dynamical systems operating close to a
phase transition or
bifurcation point between two different types of dynamical behavior. Such close-to-critical systems are often observed to exhibit behavior that is
intermediate between "order" and "chaos". Three other stars in the Kepler Input Catalog likewise exhibit similar "avalanche statistics" in their brightness variations, and all three are known to be
magnetically active. It has been conjectured that stellar magnetism may be involved in Tabby's Star. According to Steinn Sigurðsson, the megastructure hypothesis is implausible and disfavored by
Occam's razor and fails to sufficiently explain the dimming. He says that it remains a valid subject for scientific investigation, however, because it is a
falsifiable hypothesis. Due to extensive media coverage on this matter, Tabby's Star has been compared by Kepler's Steve Howell to , a star with an odd light curve that was shown, after years of research, to be a part of a five-star system. The likelihood of extraterrestrial intelligence being the cause of the dimming is purely speculative;
Exomoons Two papers published in summer 2019 offered plausible scientific scenarios involving large
moons being stripped from their planets. Numeric simulations were performed of the migration of gas giant planets, and their large gaseous moons, during the first few hundred million years after the formation of the planetary system. In approximately 50% of the cases, the results produce a scenario where the moon is freed from its parent planet and its orbit evolves to produce a light curve similar to that of Tabby's Star. ==Follow-up studies==