The brightness of a star naturally changes throughout its life cycle, but that takes ages and we humans are but a blip on the cosmic timeline. When we see a star’s brightness change, it’s an indication something of cosmological significance is happening. Astronomers have had a hard time figuring out what, exactly, is happening to KIC 8462852. You may know it as Tabby’s Star, or the “Alien Megastructure Star.” It’s entered another record-setting dimming cycle of unknown cause.
Astronomers are keen to watch for dips in brightness from distant stars because we’ve learned this is an excellent way to spot exoplanets, or planets that orbit stars other than our own Sun. The Kepler space observatory has discovered thousands of exoplanets this way. Tabby’s Star first gained fame thanks to Kepler observations that showed a big drop in brightness — so big that it couldn’t have been a planet. Its overall brightness dipped by several percent and stayed like that for several days. The dimming events have continued happening, and the intervals are seemingly random.
Early on, some scientists made the semi-serious suggestion that Tabby’s Star (named after original study author Tabetha Boyajian) could exhibit such strange behavior because aliens are building giant space platforms around it. Thus, it became the “Alien Megastructure Star.” Scientists have continued monitoring the star, which is 50 percent larger than the sun and about 1,200 light years away, hoping to figure out what’s causing the dips in brightness. Some have also sought to disprove the alien hypothesis. Boyajian herself published a study early this year that claimed the best explanation for KIC 8462852 is not aliens but a giant dust cloud.
While aliens seem to be out, KIC 8462852 is still a fascinating object. Just this week it entered another dimming cycle, and it’s a big one. According to Boyajian, this is the largest dip since the star first popped up in Kepler data back in 2013 (with observations from 2011).
Starting on March 16, the star’s brightness dipped well below normal. Then on March 22, it was back up. As of March 26, the brightness was down again in a big way. It’s down at least 5 percent and as much as 10 percent. The team is continuing its observations to see how low Tabby’s Star can go. The original Kepler data showed a 22 percent drop, so we might still have a way to go.
This might not be as interesting as aliens building a Dyson sphere, but it’s still a fascinating star.