Alien megastructure mystery a step closer to being solved?

The mystery surrounding the star KIC 8462852 may be a step closer to being solved. Scientists have discovered another very young star that exhibits huge dimming in the same way the "alien megastructure"star does – the reason for which appears to be a massive disk of dust.

KIC 8462852 made headlines at the end of last year when scientists noticed unusual dips in its brightness.

A star will get dimmer when something passes in front of it – a planet the size of Jupiter, for example, would block around 1% of our Sun's light. However, this star was showing dips of up to 20%, meaning something enormous must be blocking its light.

A number of proposals were put forward, the most out-there being that an advanced alien civilisation had built a huge structure around it to harness its energy. Scientists are yet to come up with a plausible explanation.

EPIC 204278916 is a young star, between five and 11 million years old, and was discovered with Nasa's Kepler spacecraft two years ago. It is about the same size as our Sun, but with half the mass. Like KIC 8462852, scientists discovered unusual dips in its brightness – only far more pronounced. The light from this star dipped as much as 65% for around 25 days over a 78 day monitoring period.

Publishing their findings on the pre-print server arxiv.org, Simone Scaringi, from the Max Planck Institute for Extraterrestrial Physics in Germany, and colleagues say the dimming of EPIC 204278916 is likely caused by a protoplanetary disk that is tilted in such a way that when observed from Earth, it blocks out the star's light.

The age of the star, they argue, gives weight to this proposal. Younger stars in the earlier stages of their formation are often surrounded by protoplanetary disks – a rotating dense disk of dust and gas. Another explanation is "transiting cometary-like objects in either circular or eccentric orbits", although this explanation has several major constraints – one of which being the huge size of the transiting clump.

But how does this related to KIC 8462852? Some scientists have argued the alien megastructure star is far younger than has been proposed. If this is the case, a similar disk of dust and gas could be shielding its light. Furthermore, they say older stars can also have circumstellar disks of dust.

They note, however, that KIC 8462852 is still an extremely unusual star. Three other stars have since been discovered that more closely resemble EPIC 204278916. Other than both having huge dips in their brightness, there are no other similarities between the two stars. Most importantly satellite imagery shows EPIC 204278916 is surrounded by a disk – which is not the case for KIC 8462852.

Regardless, they say further research will be needed to confirm the cause of dimming at the young star. "Given there is no complete explanation for the mysterious behaviour of EPIC 204278916, more observations and modelling of this system are required to fully explain the clustered large-amplitude dipping events," they wrote. "Continuous photometric monitoring of this system for subsequent dipping events will determine whether this behaviour is periodic or not ... It is thus important to monitor EPIC 204278916 before such an event occurs."