Why is this star dimming? Astronomers still don't know

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A strange star in our galaxy has officially become even more enigmatic: According to data collected by NASA’s Kepler space telescope, the star mysteriously dimmed over a period of a few years.

The star is called KIC 8462852, and it was already on scientists’ radar for fluctuations in its brightness. So two astronomers decided to study it more carefully, using images from Kepler. They discovered that from 2009 to 2012, the star’s brightness declined by just under 1 percent. Then, over a time period of six months, its brightness plunged by 2 percent. While news of their discovery first surfaced in August, their work has now been accepted for publication in an astronomy journal, the Carnegie Institution for Science announced on Monday.

“The steady brightness change in KIC 8462852 is pretty astounding,” Ben Montet, an astronomer and fellow at the University of Chicago, said in a statement. “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.”

Montet is coauthor on the new study about the star, forthcoming in the Astrophysical Journal.

“This star was already completely unique because of its sporadic dimming episodes,” Josh Simon, an astronomer at Carnegie Science, said in the statement. “But now we see that it has other features that are just as strange, both slowly dimming for almost three years and then suddenly getting fainter much more rapidly.”

One explanation for the star’s change in brightness is something like a planet or comet breaking up in front of it, although that idea doesn't fully account for the star's behavior, according to the study.

While the controversial concept that an “alien megastructure” could have caused the dimming has galvanized public interest in the star, David Kipping, an astronomer with Columbia University, said that it’s likely caused by an as-yet-to-be explained natural phenomenon.

“The confirmation that the star is dimming over time re-enforces how strange this star is,” Kipping told FoxNews.com in an email. “As yet, we do not have a natural explanation as to what is happening, but in my view this most likely represents a gap in our present knowledge rather than evidence for an alien megastructure.”

Follow Rob Verger on Twitter: @robverger