Mysterious long-term dimming of KIC 8462852 may be caused by dust, astronomers say 

Posted: October 9, 2017 by oldbrew in Astrophysics, research

Orbiting dust cloud – artists’ impression [credit: Karen L. Teramura]

An orbiting cloud of dust round ‘Tabby’s star’ may lack excitement for casual observers, but there it is – probably.

University of Arizona astronomer Huan Meng and co-authors have found the long-term dimming of KIC 8462852 — a main-sequence F-type star located in the constellation Cygnus, about 1,480 light-years from Earth — appears to be weaker at longer infrared (IR) wavelengths of light and stronger at shorter ultraviolet (UV) wavelengths, reports

Such reddening is characteristic of dust particles and inconsistent with more fanciful ‘alien megastructure’ concepts, which would evenly dim all wavelengths of light.

The study is published in the Astrophysical Journal ( preprint).

KIC 8462852, also known as Boyajian’s star, Tabby’s star, TYC 3162-665-1 or 2MASS J20061546+4427248, captured astronomers’ imagination in September 2015 with its strangely fluctuating brightness. Ever since then, the scientific community has been observing this enigmatic character and sifting methodically through the data in search of an answer.

Speculation to account for KIC 8462852’s dips in brightness has ranged from it having swallowed a nearby exoplanet to a swarm of exocomets orbiting the star to a Dyson sphere, a hypothetical energy-gathering structure built by an advanced civilization.

To test multiple hypotheses for the behavior of the star, Dr. Meng and colleagues obtained measurements of the star over a wide wavelength range from the UV to the mid-IR from October 2015 through December 2016, using NASA’s Spitzer and Swift missions, as well as the Belgian AstroLAB IRIS observatory. They found less dimming in the IR light from the star than in its UV light.

Any object larger than dust particles would dim all wavelengths of light equally when passing in front of KIC 8462852. “This pretty much rules out the alien megastructure theory, as that could not explain the wavelength-dependent dimming,” Dr. Meng said. “We suspect, instead, there is a cloud of dust orbiting the star with a roughly 700-day orbital period.”

Continued here.

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