This Star Has Been Slowly Dimming for 100 Years

Beyond its sudden dramatic dips, Tabby's Star hides a second, slower mystery: it appears to have been fading for more than a century.

The short dips grab attention, plunging the star's light by up to 22 percent in days. But underneath them runs a much quieter, long-term decline.

When astronomers dug up old photographic plates, some over a hundred years old, they found signs the star has slowly grown dimmer over that time. That is strange on its own. A normal star should not steadily fade over a human lifetime. So the puzzle has two layers: the fast, deep dips lasting days, and a gradual, century-long dimming underneath. Any explanation has to account for both at once.

The leading idea is that one thing causes all of it: enormous, uneven clouds of dust around the star, thick enough in places to cause sudden dips, and spread widely enough to slowly dim the star over decades. Strange, but far more likely than anything artificial.

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