The infamous "alien megastructure" star is back, and astronomers are grabbing their telescopes

Scientists around the world were shocked when a mysterious “alien megastructure” star suddenly went dim on May 18.

Astronomers have had their eye on the star — also known as Tabby’s star — since 2009, when it was first discovered by Tabetha Boyajian at Louisiana State University. It’s special because its bright lights dim and flicker in a random, unidentifiable pattern, which is really strange, as far as star behavior goes.

“The weird thing about this star is the constant brightness for so long, then the unpredictable, relatively short periods of dimming,” Matt Muterspaugh, astronomer and professor at Tennessee State University, said. "It’s been four years since scientists last noticed the star dim," Muterspaugh said, and information about it only became available three months after the star had dimmed.

“This is exciting because it’s the first time we’re seeing it happen in real-time,” he said.

The alien megastructure star’s tiny light show caused a breakout of excitement on Twitter as scientists scrambled to share what they're seeing. In the past, the star's brightness has dipped by about 20%.

“Over the past four days, it has been pretty much constantly paying attention to this star,” Muterspaugh said. He estimated that up to 20 labs and observatories are monitoring it right now. “It has been a really great team effort by the astronomical community.”

Researchers previously theorized that bright lights orbiting a star could indicate technological inventions made by space civilizations — perhaps aliens build these machines to harness energy from the stars, for example. That’s how “Tabby’s star” also became known as “alien megastructure star.”

“Aliens should always be the last hypothesis you consider, but this looked like something you would expect an alien civilization to build,” astronomer Jason Wright told the Atlantic in 2015.

Others have said that these “alien megastructures” orbiting the stars are probably just comets, but scientists haven’t completely abandoned the idea of aliens just yet.

“Right now, the alien hypothesis — we can’t rule that out,” Muterspaugh said. “Right now, we’re really trying to collect the data to tell us more about whatever is causing this.”