dyson sphere
Artist's impression of a Dyson SphereKevin Gill/Flickr, CC BY-SA

There are still no signs of aliens in the area around KIC 8462852, the "alien megastructure" star located more than 1,400 light years from Earth, Seti International has said. Astronomers have been studying the star for the past few months after it showed patterns of dimming never seen before – more than 20% of its light was being blocked out by something, 20 times more than a large planet like Jupiter would when it passes in front.

A number of theories as to what could be causing this dimming have been suggested. One is that a planetary collision has taken place in KIC 8462852's system, while another is that a nearby star has knocked thousands of comets from their normal place. However, a third and more exciting possibility is that of an alien megastructure.

The idea of these megastructures was first proposed by Freeman Dyson in the 1960s. He said an extremely advanced alien civilisation would eventually learn to harness energy directly from the sun by building a massive "Dyson sphere" around it. So when the dimming star was noticed, Seti International astronomers began focusing their attention on it, looking for possible signals that could be from extraterrestrials. Seti International is a new research and educational organisation. It was founded in July 2015 and is "devoted to innovative approaches to astrobiology and the Search for Extraterrestrial Intelligence (SETI)".

In November, Seti said it had found no radio signals coming from that part of space in the frequency ranges it used. But this did not deter it from continuing to look: "Clearly, the energy demands for a detectable signal from KIC 8462852 are far higher than this terrestrial example (largely as a consequence of the distance of this star)," Seti wrote.

alien megastructure
Artist impression of an alien megstructureSeti International

Now, scientists from Seti International have announced further findings from their observations. In a paper submitted to the Astrophysical Journal Letters, the authors searched for laser pulses as short as a billionth of a second from the Boquete Optical Seti Observatory in Panama.

"Given the large distance to KIC 8462852, nearly 1,500 light years, any signal received on Earth today would have left the star shortly after the fall of the Roman Empire," said study author Marlin Schuetz. "We need a sensitive way to detect any laser pulses that have travelled that far."

Over six nights, they looked for intentional laser pulses sent towards Earth. The team used a new method of detecting brief laser pulses using a single photometer that receives a full stream of pulses. They then analysed the output to look for a regular periodical signal – a sign of an artificial signal – but it came up blank.

"The hypothesis of an alien megastructure around KIC 8462852 is rapidly crumbling apart," said Douglas Vakoch, president of Seti International, who was also an author on the paper. "We found no evidence of an advanced civilization beaming intentional laser signals toward Earth."

Nevertheless, the team said carrying out these sorts of experiments is important for future alien research. "If some day we really detect a signal from an extraterrestrial civilization, we need to be ready to follow up at observatories around the world, as quickly as possible," Vakoch said.