Bodman & Quillen (2016) argued that a single comet can not produce a dip in the light
curve as deep and as long as the two major events observed in Q8 and Q16. They propose that
a swarm of at least 30 comets traveling in a tight pack can explain the events during the two
last quarters, Q16 and Q17. The dip in Q8 can not be explained by the same swarm of objects,
however. This interpretation invokes multiple groups of comets in significantly different orbits
around the star, speculatively indicating the start of a Late Heavy Bombardment episode.
We propose a different interpretation which is consistent with the observed peculiarities of the Kepler data and other information about the star. We consider a large swarm of interstellar
objects ranging in size from small comets to planetoids unrelated to the target star, traveling
in the interstellar space, which happened to cross the line of site to the target and, perhaps,
its near neighbors on the sky. The irregularly spaced events are explained as randomly timed
occultations from different parts of the swarm. Such free-traveling swarms can be the remnants
of catastrophic disintegration of a rich exoplanetary system or a star-formation episode in a
depleted molecular cloud. The interstellar Na D absorption lines detected by Boyajian et al.
(2016) are likely to be related to the foreground cloud. The existence of interstellar comets
has been suspected for some time but no direct evidence has yet been found. Alternatively, a
swarm of comets orbiting another foreground star which accidentally happened to be close to
the target star in the sky projection (an optical pair) can also be considered.
What kind of density should a swarm of comet-like or planetoid-like objects have to
produce the observed rate of irregular occultations? Assuming a radius of 1.7 R⊙ for KIC
8462852 (Huber et al. 2014) and a distance of 500 pc to the star, the cross-section of the
occultation events during the 4 years of Kepler main mission is 0.125×10−6µ in arcsec2
A smaller distance to the star implies a higher relative
A cloud of foreground comets, whether solivagant (traveling by themselves) or attached to
a foreground star, analogous to our system’s Kuiper belt, could explain the irregular arrival of
occulters, the varying depth and duration of observed dips, and the magnitude of these events.
Giant comets are no longer required, as a closer body of regular size obstructs more light from
the target star.