A leading expert on the hunt for ET has poured cold water on the claim that a star that is displaying mysterious changes in brightness could be surrounded by a giant artificial structure built by advanced aliens. 

One artist’s impression of a Dyson sphere-type structure surrounding a star. Image credit: Kevin Gill/Flickr, CC BY-SA

Duncan Forgan, a researcher into planet formation and astrobiology, has previously proposed a search for such objects, which he says might be used to collect a star’s radiation or to steer it away from danger.

But Dr Forgan told Skymania that he agrees with a team that checked out possible causes for the changes in the star KIC 8462852 and decided they are probably due to comet fragments blocking out the starlight. An ET explanation would require “extraordinary evidence”, he said.

KIC 8462852, which lies about 1,500 light-years away in the constellation of Cygnus, was studied by NASA’s Kepler space telescope, which searched for exoplanets orbiting distant stars by watching for dips in those stars’ brightnesses.

Many hundreds of such planets were discovered during the first phase of its mission. More have been found in the data by a citizen science project called Planet Hunters, that is part of the Zooniverse network. But this keen band of volunteers spotted the odd behaviour of KIC 8462852 and called attention to it.

The chief scientist behind Planet Hunters, Tabetha Boyajian, of Yale University, New Haven, CT, led research to try to discover why the star was behaving oddly. Her team concluded that the comet-fragment hypothesis was the most likely. However their paper sparked speculation in some quarters that the cause might instead by an alien-built artifice such as a Dyson sphere.

The case was interesting enough for astronomers working for SETI (the Search for Extra-Terrestrial Intelligence) to begin monitoring the star last week with a network of 42 radio dishes called the Allen Telescope Array.

Dr Forgan, of the School of Physics and Astronomy at the University of St Andrews in Scotland, told Skymania: “I think this is clearly a very weird and interesting system, and the team who analysed the data for this system have struggled to find a clear answer as to what is causing the dips in the light curve.

“At the moment, a collection of comets is the best fit to the data, and I would agree with the team’s analysis. Obviously, any system which looks anomalous is going to be interesting to SETI scientists, but we have to be rational about this. Proposing ET as the cause of these observations is an extraordinary claim, and therefore needs extraordinary evidence.

“To quote Sherlock Holmes: ‘Eliminate all other factors, and the one which remains must be the truth. We haven’t yet eliminated the other non-artificial explanations for the data. By Occam’s razor, the simplest explanation is likely to be the correct one, and we don’t need to propose an advanced technological civilisation if comets (which I expect are a far more common occurrence in the Universe) will do the job.”

Dr Forgan is calling for more investigation into KIC 8462852 to learn more about it. He told Skymania: “What we really need here is more data. Data of every kind. To solve this puzzle, we need to observe the system at several different wavelengths, especially in the infrared, to learn more about its dust, asteroid and comet population. Observing in the radio will help us test the ET hypothesis further, and it will teach us about the star as well.”

He concluded: “In short: a very interesting system, but we aren’t in a position to declare ‘Aliens!’ yet. Additionally, no-one in the SETI community (especially Wright et al in the G-Hat group) is yelling ‘Aliens!’ either, but are just curious to learn more about this system.”

Jason T Wright is leader of the project known as G-HAT (Glimpsing Heat from Alien Technologies Survey). Having used NASA’s WISE satellite to search 100,000 galaxies for particular radiation that could indicate colonisation by an advanced, spacefaring civilisation, the G-HAT team had to announced in April 2015 that none had been detected.

Some of the dishes making up the Allen Telescope Array. Image credit: Colby Gutierrez-Kraybill CC BY-SA

Dr Forgan has previously told us that he believes advanced aliens might have built giant artificial structures around other stars which optical telescopes could identify from the nature of the starlight.

He said: “The classic suggestion is that energy-hungry aliens might have built something called a Dyson sphere, which completely encircles a star and collects all its radiation. Some American teams are already looking for odd-looking stars that might appear very big and very cool.

“My idea is to look for a variant that is not the full sphere but a spherical arc around the star, built to steer the star onto a different path. The inside of the arc is mirrored so that any radiation that comes from the star gets reflected back to the star.

“Stars are a balance of the radiation coming out and the gravity trying to pull it back in, so when you upset that balance by putting in this mirror then you create a force and the force pushes the star in a direction.

“So it is a way of giving the star a nudge to push it out of the way of something dangerous, perhaps a cloud of molecular gas that might disrupt the star’s magnetic field on which aliens relied to protect themselves from deadly radiation.

“Other people have even suggested that when your star is about to die, you could use it to push your planetary system somewhere else and give your planets to a new star!”

Dr Forgan took a moment to support the work of assistant professor Wright’s alien-hunting efforts with G-HAT at Pennsylvania State University. He said: “I think the media are doing Wright a disservice, and painting him as a crackpot, when he is responsible for some of the most level-headed dialogue on this issue.”