Star Tabby: Strange dips in brightness are a bit baffling

Star Tabby: Strange dips in brightness are a bit baffling

By Phil Plait A paper by a team of astronomers is getting some notice because of aliens. Now let’s have a care here. The paper doesn’t mention aliens, and it doesn’t even imply aliens. Not directly, at least. But the astronomers found a star so odd, with behavior so difficult to explain, that it’s clear something weird is happening there. And some of the astronomers who did the work are now looking into the idea that what they’ve found might (might!) be due to aliens. But don’t let this idea run away with you (as it has with some folks on social media and, no doubt, will in some sketchier “media” outlets any minute now). The scientists involved are being very skeptical and approaching this the right way: more of an interested “Hey, why not?” follow-up, as opposed to the Hollywood renegade astronomer who just knows it’s aliens but (fist shaking in the air) just can’t convince those uptight Big Astro sellouts! But it’s cool either way. OK, so first, what’s the science? The star is called KIC 8462852, and it’s one of more than a hundred thousand stars that was observed by NASA’s Kepler mission. Kepler stared at these stars, looking for dips in their brightness. These very slight dimmings can be due to many factors, but one is if the star has planets, and one (or more) of them orbits the star in such a way that it passes directly in front of the star as seen from Earth. If it does—what we call a transit—we see a tiny diminution of starlight, usually by less than a percent. Thousands of exoplanets have been found this way. Usually the planet is on a short orbit, so the dip we see is periodic, repeating every few days, weeks, or months, depending on the size of the planet’s orbit.
KIC 8462852 is a star somewhat more massive, hotter, and brighter than the Sun. It’s about 1,500 light-years away, a decent distance, so it’s too faint to see with the naked eye. The Kepler data for the star are pretty bizarre: There are dips in the light, but they aren’t periodic. They can be very deep; one dropped the amount of starlight by 15 percent, and another by a whopping 22 percent!
Click to Enlarge Click to Enlarge - Kepler data show huge dips in brightness, up to 22 percent in the star. The bottom axis is days after an arbitrary date, and the bottom two panels are close-ups of the top one, centered near 800 days (left) and 1,500 days (right). The average amount of starlight over time is set equal to 1 for ease of display.
Read More: Slate’s Bad Astronomy Blog
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