One outlandish hypothesis suggests the star's light signal is caused by a Dyson sphere, an alien megastructure designed to capture solar energy. Credit:Artist's impression by CapnHack "Aliens should always be the very last hypothesis you consider," Penn State astrophysicist Jason Wright told The Atlantic. "But this looked like something you would expect an alien civilisation to build." The light from the star is "consistent with a swarm of megastructures" around it, he said. The star has the cumbersome name of KIC 8462852, but the research group that will look for "unambiguous indicators" of technology in the star system has renamed it WTF 001 – What the Flux. (Flux is the measured light from a star that reaches Earth). "This is analogous to when pulsars were first discovered," Dr Siemion told Fairfax Media. "They were identified as 'LGM' for little green men. So we are using WTF, partly in jest but partly to reflect the fact that we truly do not know what the changes in flux [in this star] are due to."

KIC 8462852 has been informally renamed WTF 001. Credit:arXiv It is not unusual for a star's light to be blocked; periodic dimming of stars is one of the best ways to determine whether a star system has exoplanets – planets orbiting suns outside our solar system. However, such planets typically dim a star's brightness by no more than 1 per cent – and they do so in a very regular cycle, indicating the orbital period of a planet. The Very Large Array radio telescope in New Mexico. Credit:Courtesy of NRAO/AUI and NRAO Whatever is blocking this star is very irregular and can block up to 22 per cent of its light.

"It's certainly weird," said Alan Duffy, Swinburne University astronomer. "It's hard to imagine how you could block 20 per cent of light from a star. A star is huge. How do you block that much of it?" Andrew Siemion, director of the Search for Extraterrestrial Intelligence at the University of California, Berkeley, says the star is his organisation's candidate number one. "We are running out of ideas as to what could be causing this dimming," said Dr Duffy, who is not associated with the study of the star. According to Tabetha Boyajian, a postdoctoral astrophysicist at Yale University, the most likely natural explanation is that light from the star is being blocked by a massive swarm of comets that has descended close to the solar mass. KIC 8462852 with its companion red dwarf star. Credit:arXiv

Her work is based on a discovery made by a group of citizen scientists through the Planet Hunters project. They discovered the unusual light signal while looking through data from more than 150,000 stars collected by the Kepler space observatory. A paper Dr Boyajian published in September in arXiv methodically discounts what couldn't be affecting the star's light: it's not the star pulsing, it's not affected by a nearby dwarf star, it can't be a dust cloud caused by an asteroid or planetary collision. Swinburne astronomer Alan Duffy says Parkes has "key scientific capacity that we would not want to lose". Dr Boyajian suggests that the nearby dwarf star could have disrupted a cloud of orbiting comets and sent them crashing in to a closer orbit. But she accepts that her paper only considers natural scenarios. She told The Atlantic that there were "other scenarios" she was considering. Dr Wright at Penn State is about to publish an alternative explanation for the star's light patterns. He told The Atlantic the patterns of light are also consistent with a "swarm of megastructures" orbiting the star, perhaps formed by enormous solar collectors.

Illustration: Cathy Wilcox Such energy collectors are dubbed Dyson structures, named after physicist and mathematician Freeman Dyson, who suggested in 1960 that advanced civilisations would use such structures to collect massive amounts of solar energy. Dr Wright and Dr Boyajian are now working with Dr Siemion at SETI to work out WTF the star actually is. Their research team will use the radio telescope at Greenbank, West Virginia, to see if there are any clear signals of electromagnetic energy in a narrow frequency range that could indicate radio technology. If they get anything unusual, they will use the Very Large Array radio telescope in New Mexico to get a clearer picture. Dr Siemion said that "as scientists we need to say that the probability that this is due to some sort of technology is very, very low, but it certainly warrants follow-up and that's exactly what we are going to do."