Tuesday, October 17, 2017
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Tabby’s Star


In the universe, there is a multitude of  fascinating stars, from Sirius, a star so large that if it was placed at the center of the solar system it would extend past Jupiter, to quark stars, neutron stars with gravity so strong that the neutrons at the core dissolve into their component quarks. However, one of these phenomena in particular stands out. Meet KIC 8462852, or Tabby’s Star, located in the constellation Cygnus, around 1000 light-years away. First discovered in the mid-1800s, nothing remarkable was found about this star. However, in 2011, when the Kepler Space Telescope, a telescope specially designed to find exoplanets orbiting around distant stars, trained its eye on this star for several years in a row, it found something very different from what it was searching for.

Astronomers use a unit of measurement called magnitude to show the brightness of a star. The lower the magnitude, the brighter the star. Magnitude operates logarithmically, like the decibel system, so for a star to increase its brightness by a magnitude of one, it has to become 10 times brighter. Sirius, the brightest star in  our sky, has a magnitude of 1.4, while the dimmest known star, a red dwarf in the Lepus constellation, has a magnitude of 21.1. Tabby’s star has, as a baseline, a magnitude of 3.05. While Kepler was observing it, the star’s magnitude has been seen to increase by over .1, or 22%! If a Jupiter-sized exoplanet crossed over the star, it would only decrease the luminosity by 1%. If this wasn’t crazy enough, the star’s luminosity in general has been going on a downwards trend, as shown in the graph below.

There have been several hypotheses about these very strange occurrences, but not a single one has answered this problem to satisfaction. One possible explanation was a large cloud of comets and other space debris blocking the light from the star. However, the sheer amount of debris needed for this to be a plausible explanation is far too much. Imagine the number of comets needed to be able to provide the amount of surface area similar to a planet twenty-two times the size of Jupiter. A bit absurd, if you ask the world’s astrophysicists. Another possible explanation could be a massive planet. If calculations are run, a ringed planet 5 times the size of Jupiter with a trail of asteroids could theoretically call for the 22% dimming of the star. However, orbiting planets produce very predictable dips, and Tabby’s Star has been anything but predictable. The final plausible theory presented was the idea of a planetary collision spreading hot dust all over the star, obscuring it. This idea held some merit until scientists pointed an infrared telescope at Tabby’s Star. Hot dust, like everything else hot, produces radiation. If the dimming was truly caused by a planetary collision, a large amount of infrared light would be coming from the system. However, the infrared telescope failed to find anything past the usual levels of infrared expected for the star.

Since all of the conventional theories have been disproven, astrophysicists have been forced to think about more unorthodox explanations, most notably aliens. It is possible that an advanced civilization is creating a Dyson Sphere, a hypothetical megastructure that advanced civilizations could build around a star to harvest its energy, around Tabby’s Star, slowly dimming it as the shell obscures the light from the star. This theory is obviously quite outrageous, and in general scientists will only accept this theory if literally everything else is improbable or some evidence comes up, but hey, it’s fun to dream!

Sources:

https://www.aavso.org/aavso-alert-notice-579

https://phys.org/news/2006-02-strange-stars.html

http://simbad.u-strasbg.fr/simbad/sim-id?Ident=TYC+3162-665-1

https://arxiv.org/abs/astro-ph/0307429

(for the graph): http://www.info-quest.org/seti.html