THE possible existence of an alien megastructure orbiting a mysterious star in the Milky Way is one of the more far fetched theories banded about by imaginative stargazers — but it’s not going away.

Over the past weekend astronomers were rushing to fix their telescopes on the mysterious star which spawned the theory because it was, once again, acting strangely.

Known as Tabby’s Star, or KIC 8462852, the odd pattern of light emitted from the star located about 1500 light years away continues to leave scientists puzzled since it’s strange luminosity was noticed in recent years.

The star’s observed brightness dips by about 20 per cent, an unexplained phenomena that has led to a number of theories, some more sensational than others.

On Friday night astronomer Jason Wright from Penn State University — the same academic who recently wrote a paper about the hypothetical existence of an indigenous alien species in our solar system before humans — noted that the brightness of Tabby’s Star was dipping again.

ALERT:@tsboyajian's star is dipping



This is not a drill.



Astro tweeps on telescopes in the next 48 hours: spectra please! — Jason Wright (@Astro_Wright) May 19, 2017

The star is named after astronomer Tabetha Boyajian who first reported on the star’s seemingly strange behaviour after analysing data from the Hubble Telescope.

She has been posting recording of the star’s dimming over the past few days with great excitement.

the newest light curve for #TabbysStar from LCO 0.4m scopes shows it has a complex shape. And its not over yet! @LCO_Global pic.twitter.com/wsIKK0JLJI — Tabetha Boyajian (@tsboyajian) May 21, 2017

But we still have no idea why the star appears to be flickering.

One of the most favoured explanations for seemingly random light fluctuation is that a swarm of comet fragments is periodically blocking light from the star. Another very similar theory contends it could be the debris of a destroyed planet that is blocking the star’s rays, however such a theory struggles to explain the irregularity of the dimming.

Another technically possible explanation that has been banded about — and gained much attention in the media — is the idea that an alien megastructure has been responsible for blocking the star’s light.

It’s a notion that has its origins in an idea put forth by physicist Freeman Dyson who proposed that a massive orbiting array of solar collectors (which has become known as a Dyson structure) would be a perfectly rational thing for an alien society to build to meet its energy needs.

Of course, scientists think that’s hugely improbable.

Last year SETI (Search for Extraterrestrial life Institute) announced it was going to focus on the star in a bid to get to the bottom of the mystery.

Dan Werthimer, a chief scientist at Berkeley SETI, was quick to dismiss the wild theories of an alien megastructure.

“I don’t think it’s very likely — a one in a billion chance or something like that — but nevertheless, we’re going to check it out,” he said.