spaceSpace and Physics

Astronomers Have A Clever New Theory About The Alien Megastructure Star


Robin Andrews

Science & Policy Writer

Nope, not a disintegrating planet... but close! NASA/JPL-Caltech

The wait is over. Finally, today, we can exclusively reveal that the mystery behind the so-called “alien megastructure star” has been solved. Yes, ladies and gentlemen: it was aliens all along, and they’ve got themselves one hell of a megastructure.

Only kidding – but hey, you know that’s what you all want it to be. Well, we hate to disappoint you, but a new arXiv paper explaining the star’s unusual behavior doesn’t involve interstellar beings after all. It’s much more likely that the mystery figure in this puzzle is a ringed gas giant, much like Saturn.


First, a little recap for the uninformed. Tabby’s star – named after Dr Tabetha Boyajian, who first discovered and documented the strange celestial behavior – noticed in 2015 that her bright, soon-to-be namesake kept experiencing inexplicable and significant dips in brightness.

This suggested that one of two things was occurring. Either an internal process was triggering the unpredictable dimming, or something was moving erratically in front of the star. Normally, dimming is a sign that a planet is shifting in the direct line of sight between the star and Earth, but planets have regular orbits – and this dimming was happening somewhat randomly.

Almost immediately, academics, the press, and the public began to suggest a range of possible hypotheses, ranging from the sensible (a self-destructive swarm of comets) to the outright unlikely (an alien megastructure).

The number of comets required to explain the dimming is an absurdly high number, one thought to be physically impossible. It also can’t be explained away as a variable star – one whose brightness naturally changes over time – because observations show it’s a stable main sequence star, one that should only show minor alterations in brightness, not the major changes observed in real life.

Is a ringed exoplanet to blame? Nostalgia for Infinity/Shutterstock

So what’s going on? A team from the University of Antioquia in Colombia think they have the best idea yet: it’s a ringed planet, with a twist.

Using a series of mathematical simulations, the team calculated that if a ringed gas giant was orbiting close to the planet, it would produce significant and irregular dips in brightness. The fragmented mass of rock, dust, and ice would cleave across the star’s path first, then the planet itself, then the rings.

This alone doesn’t explain quite how random the dips in brightness are, though. The team’s models reveal that, as the gas giant is so close to Tabby’s star, the immense gravitational well would cause the planet to wobble eccentrically – and this added complexity would fully explain the strange light patterns of the mysterious star.

Are they 100 percent sure that this is what’s going on? Of course not – but it’s an intriguing new idea, and one that’s yet to be debunked like all the rest.



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