Posted October 16, 2015

Where little green men probably don't live

What causes the weird dips in the light of a star 1500 lightyears away? Nobody knows but many people speculate.

In 1967 the astronomy world was abuzz about a unique and inexplicable discovery. Something in the sky broadcast extremely regular blips, about three times every four seconds. A cosmic beacon from an extraterrestrial intelligence? At first the mysterious source was christened LGM-1, for Little Green Man. But there turned out to be a natural explanation. Astronomers now know many such blipping heavenly objects. They call them pulsars and it's a well established fact that they are exhausted, dying, rapidly rotating stars.

Now, in 2015, there is another unique and inexplicable discovery. With the help of amateurs studying raw data, astronomers have found a star with peculiar behaviour. The star goes by the beautiful name of KIC 8462852. It's in the constallation of Cygnus (Swan) and it has magnitude 12, meaning it is way too faint to be seen with the naked eye.

It is one of the 150,000 stars that the space telescope Kepler had studied. Kepler is on the lookout for stars that may have planets orbiting them. One way of finding those is looking for dips in a star's light, that may be caused by a planet passing in front of the star and partially eclipsing it. Such events, even if caused by a Jupiter-sized planet, tend to cause a decrease of about 1% in the light that reaches us from the mother star.

The light emitted by KIC 8462852 has decreased a few times by much more. Something caused a dip of 15% in early 2011 an another one of 22% (accompanied by a lot of smaller dips), about 730 days later in early 2013. 22% is HUGE, like inexplicably huge. To obscure a star by almost a quarter, a solid body would need to have half the diameter of said star and pass almost exactly in front of it. But an object that big would almost certainly be a visible star itself. Also it would make KIC 8462852 move back and forth in our direction. This would cause a measurable 'doppler shift' in the frequency of the starlight, and no such shift has been found.

In a scientific paper a group of professional and amateur astronomers investigate a number of other possible explanations, ruling them out one by one. There is just one they don't reject outright: a cloud of comets that might have been torn loose from the local comet cloud around KIC 8462852, when another star passed close by. But they don't consider the case closed, as they urge that KIC 8462852 be monitored for more dips. One could have occurred in April 2015 but no telescope was looking at the time. The next - if the 730 day interval holds up - will be in May 2017.

Meanwhile, the researchers are thinking in a different direction too. Lead author Tabetha Boyajian tells The Atlantic that she is co-writing a proposal to have a radio telescope look at frequencies associated with technological civilizations. The occultations might just be caused by parts of a Dyson sphere that harvests energy for the local aliens. Observations could take place in January.

But as astronomer Jason Wright tells The Atlantic: 'Aliens should always be the very last hypothesis you consider.' We at Join the Brightest Minds can't help noticing that if an orbiting solar plant were to blame, the two observed dips should resemble one another very much - which they don't. So it seems a lot more probable that something natural is going on.

About Herbert Blankesteijn

Herbert Blankesteijn is a technology journalist from the Netherlands who has written for many prominent Dutch newspapers. He presented and directed television and radio programmes and has 10 books to his name. Herbert is interested in nascent fields such as 3D printing, drones, robotics and the private space business.