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You know what, maybe Tabby's star ate a planet, ponder space eggheads

So much for the 'alien megastructure' theories

By Richard Chirgwin, 13 Jan 2017

Tabby's star – formally KIC 8462852 – has attracted a new and possibly-plausible explanation for its excess of twinkle: the remnants of a planet destroyed in a collision.

That hypothesis comes from Brian Metzger and Nicholas Stone of Columbia University's Astrophysics Laboratory, and Ken Shen of UC Berkeley's Department of Astronomy and Theoretical Astrophysics Centre.

Over at Arxiv, they explain a hypothesis that's a lot more plausible than the “alien megastructure” idea that occupied a lot of synapses in 2016.

In case this is the first you've heard of Tabby's star: it's a mostly unremarkable F-type main sequence star with just one interesting characteristic, it's light isn't stable. It shows both short term “twinkles” and a long-term dimming.

Since it was the first time such a phenomenon had been observed, there was no straightforward explanation for its dimming. Possibilities offered up included instrument calibration (debunked), a comet halo (also debunked), and most famously, a partly-constructed “Dyson sphere” (which NASA played killjoy about).

Metzger, Nicholas and Shen write that they took their idea from “an initial suggestion by Wright & Sigurdsson” and, doing the maths, suggest a planet spiralled into the star, leaving debris that causes the dimming.

The paper suggests a collision could leave two artefacts:

  • A brightening that happened before it was observed, followed by a long-term dimming which is in observations between 1890 to 1989. This was caused by “gravitational energy released as the body inspirals into the outer layers of the star”; and
  • Transient dimming “due to obscuration by planetary debris from an earlier partial disruption of the same inspiraling bodies, or due to evaporation and out-gassing from a tidally detached moon system”.

The paper notes that since one star is exhibiting two unusual phenomena, it's reasonable to suggest they're related.

Vulture South isn't up to the task of assessing the science, but we'll happily predict this won't be the end of the controversy. ®

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