Mystery Grows for Strange Star- “It’s Doing Things We’ve Never Seen Before”

When the observations and analysis of the star known as KIC 8462852 were posted to a preprint server in August, they caused quite a commotion due to their unusual nature.

And now that those findings and observations have been officially published by The Astrophysical Journal, it turns out KIC 8462852 is even stranger than previously thought.

A sequence of brief, non-periodic dimming events observed by NASA’s Kepler space telescope reported by the study team drew initial public attention to the star. One explanation for these events is the presence of a so-called ‘alien megastructure’ circling the star. But now, the observing scientists have reported an odd twist: the star appears to be rapidly dimming.

Stars can seem to darken because a solid object such as a planet or cloud of dust passes in between it and also the observer, blocking the star’s light for a brief period of time. However, the inconsistent pattern of quick dimming and re-brightening in KIC 8462852 has not been seen any other star.

Studying a Strange Star

Inspired by a claim the star’s brightness steadily dropped by 14 percent from 1890 to 1989, the study team made a decision to investigate its behavior in a number of Kepler calibration pictures that had not been used scientifically.

“We thought that these data could confirm or refute the star’s long-term fading, and hopefully clarify what was causing the extraordinary dimming events observed in KIC 8462852,” study author Josh Simon, an astronomer at the Carnegie Institution of Science, said in news release.

The researchers discovered that, over the initial three years of the Kepler mission, KIC 8462852 diminished in brightness by nearly 1 percent. Its illumination then fell by a remarkable 2 percent over just six months, staying at around that level for the last six months of the mission.

The team then looked at more than 500 similar stars examined by Kepler and discovered that a small percentage of them exhibited fading comparable to that observed in KIC 8462852 over the first three years of Kepler pictures. However, none showed such a remarkable dimming in just six months, an overall difference in brightness of 3 percent.

“The steady brightness change in KIC 8462852 is pretty astounding,” said study author Ben Montet, an astronomer at CalTech. “Our highly accurate measurements over four years demonstrate that the star really is getting fainter with time. It is unprecedented for this type of star to slowly fade for years, and we don’t see anything else like it in the Kepler data.”

The study team said the best proposal thus far for describing the observations might be the collision of a planet or comet in the star’s system, which would result in a cloud of dust and debris that obstructs some starlight. However, this scenario wouldn’t describe the longer-term dimming witnessed during the first three years of Kepler and indicated by observations of the star dating back more than 100 years.

“It’s a big challenge to come up with a good explanation for a star doing three different things that have never been seen before,” Montet said. “But these observations will provide an important clue to solving the mystery of KIC 8462852.”

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Image credit: NASA-JPL/Caltech

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