Milky Way’s “most-mysterious star” continues to confound | Carnegie Institution for Science
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The latest findings from Carnegie’s Josh Simon and Benjamin Shappee and collaborators take a longer look at the star,
going back to 2006—before its strange behavior was detected by Kepler. Astronomers had thought that the star was only
getting fainter with time, but the new study shows that it also brightened significantly in 2007 and 2014. These
unexpected episodes complicate or rule out nearly all the proposed ideas to explain the star’s observed strangeness.
Speculation to account for KIC 8462852’s dips in brightness has ranged from it having swallowed a nearby planet to
an unusually large group of comets orbiting the star to an alien megastructure.
In general, stars can appear to dim because a solid object like a planet or a cloud of dust and gas passes between it
and the observer, eclipsing and effectively dimming its brightness for a time. But even before this evidence of two
periods of increased brightness in the star’s past, the erratic dimming periods seen in KIC 8462852 were unlike anything
astronomers had previously observed.
Last year, Simon and Ben Montet (then at Caltech, now at University of Chicago), who is also a co-author on this current
study, found that from 2009 to 2012, KIC 8462852 dimmed by almost 1 percent. Its brightness then dropped by an extraordinary
2 percent over just six months, remaining at about that level for the final six months of Kepler observations.
https://www.nasa.gov/feature/jpl/mysterious-dimming-of-tabbys-star-may-be-caused-by-dust
One of the most mysterious stellar objects may be revealing some of its secrets at last.
A new study using NASA's Spitzer and Swift missions, as well as the Belgian AstroLAB IRIS observatory, suggests that the cause of the dimming over long periods
is likely an uneven dust cloud moving around the star. This flies in the face of the "alien megastructure" idea and the other more exotic speculations.
The smoking gun: Researchers found less dimming in the infrared light from the star than in its ultraviolet light. Any object larger than dust particles would
dim all wavelengths of light equally when passing in front of Tabby's Star.
"This pretty much rules out the alien megastructure theory, as that could not explain the wavelength-dependent dimming," said Huan Meng, at the University of
Arizona, Tucson, who is lead author of the new study published in The Astrophysical Journal. "We suspect, instead, there is a cloud of dust orbiting the star
with a roughly 700-day orbital period."
