The mystery shrouding the
"alien megastructure" star KIC 8462852, also known as Tabby's star or
Boyajian's star may be one step closer to being solved. The star's bizarre
and long-term dimming has posed a mystery to scientists;
however, a new study indicates that the star's dimming is probably caused by
dust and not due to some extraterrestrial force.
The star, which is located
around 1,400 light-years away from Earth, rose to prominence a few years ago
after some scientists speculated whether the star's dimming could be caused by an alien
megastructure built around the star by some advanced and intelligent extraterrestrial civilization. Yet
another speculation also included the idea that the star swallowed an unstable
planet.
However, according to a new
study, published in the Astrophysical Journal, the star's dimming
is likely caused by an "uneven dust cloud" moving around the star.
"This pretty much rules
out the alien megastructure theory, as that could not explain the
wavelength-dependent dimming," Huan Meng, at the University of Arizona,
Tucson, the lead author of the study, said in a NASA statement. "We
suspect, instead, there is a cloud of dust orbiting the star with a roughly
700-day orbital period."
Researchers studied the star
from January to December last year, using NASA’s Spitzer and Swift space
telescopes. Scientists observed ultraviolet dips that implicate circumstellar
dust – which is dust that orbits a star. The particles are large enough not to
be blown away but small enough not to block light in all wavelengths.
Although the new study does
shed some light on what causes long-term dimming of the star, it did not solve
all the mysteries that surround the star. For instance, the study did not
explore the short-term dimming events. Scientists also still don't know what
caused a major 20% dip in brightness, which was observed by NASA’s Kepler.
What is more, in a separate
study, researchers from the Observatories of the Carnegie Institution for
Science in California also uncovered that although the star continues dimming,
it has also experienced two periods of brightening between 2009 to 2013 and
2015 to now.
"Up until this work, we had thought that the star's changes
in brightness were only occurring in one direction—dimming," Josh Simon,
lead researcher of the study said in a statement. "The realization that
the star sometimes gets brighter in addition to periods of dimming is
incompatible with most hypotheses to explain its weird behavior."
"We haven't solved the
mystery yet," Simon added. "But understanding the star's long-term
changes is a key piece of the puzzle."