Reason behind mysterious dips in brightness of `alien megastructure` star discovered

New Delhi: The Milky Way's most mysterious 'alien megastructure' star, also known as Tabby Star's strange dimming and brightening behaviour now has a reason.

According to a new study, the star's unusual dips in brightness could be due to an uneven dust cloud moving around the star, not because of a "megastructure" built by an advanced civilization.

Named after Tabetha Boyajian, lead researcher of the team that observed the celestial body in 2015 – Tabby Star has been an object of intrigue due to its strange nature.

Discovered by the NASA's Kepler Space Telescope, the KIC 8462852 has had scientists propose many theories to explain strange irregularities in its brightness, with one speculation being that the changes in brightness could be signs of activity associated with intelligent extraterrestrial life constructing a Dyson swarm.

The SETI Institute's initial radio reconnaissance of the star, however, found no evidence of technology-related radio signals from the star.

The Boyajian Star, as it is also known, was recently in the news after astronomers discovered that it had started dimming again.

Scientists do not expect such behaviour for normal stars slightly more massive than the Sun.

Speculations have included the idea that the star, more than 1,200 light-years away from Earth in the constellation Cygnus the Swan, swallowed a planet that it is unstable, and a more imaginative theory involves a giant contraption or "megastructure" built by an advanced civilization, which could be harvesting energy from the star and causing its brightness to decrease.

The findings of the new study published in the Astrophysical Journal rule out the "alien megastructure" idea and the other more exotic speculations.

Using NASA's Spitzer and Swift missions, as well as the Belgian AstroLAB IRIS observatory, the researchers found less dimming in the infrared light from the star than in its ultraviolet light.

But any object larger than dust particles would dim all wavelengths of light equally when passing in front of Tabby's Star, the study said.

"This pretty much rules out the alien megastructure theory, as that could not explain the wavelength-dependent dimming," said lead author of the study Huan Meng from University of Arizona in the US.

"We suspect, instead, there is a cloud of dust orbiting the star with a roughly 700-day orbital period," Meng said.

(With IANS inputs)