This Week’s Astronomy News: The Stars are Dimming, The Sky is Falling, and Io’s Atmosphere is Collapsing

Last fall, researchers with the Kepler Planet Hunters program announced that one of the stars they were studying, KIC 8462852, was experiencing brief but dramatic dips in its brightness, leading to speculation that the effect might be caused by extraterrestrial megastructures in orbit around the star. Although an earlier-reported finding that the star has dimmed by 20 percent over the last century may be due to inconsistencies in the telescopes being used, the Kepler Space Telescope has shown that the star, also called Terry’s Star, has indeed been dimming over the four years that the telescope was trained on that region of the sky.

For the first 1,000 days of observation, the star’s luminosity had dropped steadily by nearly 1 percent. But in the 200 days following that, it dropped another 2 percent, before leveling off in brightness for the final 200 days of observation. While other stars have been known to change in brightness over time, fluctuations in stars of this type aren’t that common, and Terry’s Star’s changes are roughly six times greater than the more dramatic of these cases. Astronomers are flummoxed as to what could be causing this dimming, as no known natural process can explain what’s happening.

The atmosphere is collapsing, at least on Io: As it turns out, the sulphur dioxide atmosphere of Jupiter’s moon Io collapses into a solid each time it makes its 42.5-hour orbit around the giant planet. As Io passes into Jupiter’s shadow, nearly the entire atmosphere rapidly cools and shrinks into a solid, forming on the moon’s surface as a sulphur dioxide frost. When it comes back out into the sunlight, the SO2 frost rapidly sublimates, turning back into a gas, reinstating Io’s atmosphere.

And lastly, the sky is falling — again! The annual Perseid meteor shower occurs this month, with the event’s peak occurring between August 11 and 13, with an expected count of 200 meteors per hour. This year’s shower is forecast to be more intense than usual, due to Jupiter’s gravity having altered the concentration of the debris field, of which originates from dust cast off of the Swift-Tuttle comet as it passes close to the Sun.