Stars twinkle and shimmer, but if one suddenly gets 65 percent dimmer in one day, then there’s something weird going on.
An international team of astronomers, led by Dr Simone Scaringi from the Max Planck Institute for Extraterrestrial Physics, has observed a young star going through irregular and extreme dimming over a period of 25 days. The object, called EPIC 204278916, is a low-mass star surrounded by a tilted protoplanetary disk, which might be the culprit of the unusual light observed.
The star was discovered by the planet-hunting telescope Kepler during its K2 mission, and it was observed for almost 79 days. Serendipitously, in the first two weeks of observation, the star's luminosity varied severely, settling on a regular variation after the 25th day.
“Other somewhat similar dipping young stellar objects have been reported in the past, but I think it is fair to say that none have been shown to display such extreme dipping behavior for such a short time,” Dr Scaringi told IFLScience.
This star will remind people of Tabby’s star, the object that became an overnight sensation for the (very remote) possibility that the dimming could be caused by a Dyson sphere, a hypothetical megastructure built by an advanced alien race to maximize the energy taken from a star.
So is EPIC 204278916 surrounded by an even bigger Dyson sphere? Almost certainly not. Observations with the Atacama Large Millimeter/submillimeter Array (ALMA) have shown that this star is not surrounded by an alien megastructure but a more “traditional” accretion disk.
“We have found it to be difficult to fully explain the observations, mostly because the transiting material needs to be very large to cause the observed dips (comparable to the size of the star) and transit the star relatively fast, but we do speculate on two scenarios,” added Scaringi.
“It is possible that the inner disk is warped with respect to the outer disk (which is resolved with the ALMA observatory). This might cause erratic dips as the material being accreted by the star is warped and blocks some of the starlight. Another possibility is that the starlight is being blocked by some transiting circumstellar clumps, possibly cometary-like debris.”
In a paper, available online and accepted for publication in the Monthly Notices of the Royal Astronomical Society, the team has excluded that the star itself is changing dramatically, although they were able to discover some regular variation that occurs as the star rotates.
EPIC 204278916 has had only one-third of the observing time as that for Tabby’s star, so future investigations should reveal more details. Kepler will re-observe the area next year, and the team is pursuing a strategy to follow this source from ground-based telescopes as well.