Boyajian's star, Tabby star, mystery, space
This artist's illustration shows comet fragments crossing the face of a star, one possible explanation for the strange dimming exhibited by Boyajian's star or Tabby star.NASA/JPL-Caltech

Tabby's Star -- the most popular strange star in our galaxy -- is acting weird again. On Friday, May 19, the F-type main-sequence star located in the constellation Cygnus started losing its luminosity by three percent and portraying mysterious dips in its brightness yet again.

Also Read: NASA: Is this man-made 'bubble' shielding Earth from strong space radiation? [VIDEO]

Several hypotheses have been proposed to explain the star's large irregular changes in brightness as measured by its unusual light curve, but none to date fully explain all aspects of the curve.

This unusual star was discovered in September 2015 by Yale University's Tabetha Boyajian and her colleagues. Initially the star was dubbed -- KIC 8462852 -- and nicknamed Tabby in the honour of Tabetha Boyajian. It was found that it dimmed over a span of seven years by almost 22 percent, before its luminosity became normal again.

Boyajian tweeted about the recurrence of loss of luminosity of the star on Friday.

Twitter/ Tabetha Boyajian

In 2016, it was revealed that the star had dimmed by 14 percent between 1890 and 1989. This finding was made with the help of old photographic plates. The star was analysed by Kepler space observatory and it was found to fade by three percent more over four years.

Researchers came up with numerous hypotheses behind the mysterious behaviour of the star. Some came up with the theory that the interior dynamics of the star are responsible for the dimming, while others blamed it at the group of space dust and asteroids.

The most popular theory formulated by some researchers is that an alien megastructure orbiting around the star has caused the depletion in the radiance of the star.