2 Tabby’s Star
In 2011, scientists studying data captured by NASA’s Kepler spacecraft discovered that a star named KIC 8462852 frequently dimmed before brightening up again. The star is also known as Boyajian’s star or Tabby’s star.
Scientists proposed several causes for this bizarre behavior. Some suggested that the dimming was caused by a group of comets orbiting the star or some other unconfirmed materials in our solar system. Others think that it is caused by the dust around a black hole between Tabby’s star and Earth.
One group of astronomers believed that this effect was generated by a megastructure built by some intelligent life. They think that the star dimmed when the orbiting megastructure passed between the star and the Kepler space telescope. This suggestion generated the most curiosity, causing other scientists to try to determine the real cause of the dimming event.
Dozens of telescopes observed the star when it dimmed again in May 2017. Scientists soon discovered that this was not caused by a megastructure because such an object would block all colors of the star’s light from reaching the telescopes rather than simply dimming it. Scientists concluded that the dimming effect happened due to space dust orbiting the star.
However, they could not decide on the origin of the dust or confirm whether it is really dust. It also seems like the dust is being blown away from the star. This is why some scientists think that an undiscovered celestial body is creating more dust to orbit the star.
In 2016, Brian Metzger of Columbia University suggested that the dust was released from a planet or moon destroyed after straying too close to Tabby’s star.