Jupiter's Moon Europa Helps Solve Stripey Mystery

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Last year, something strange happened to Jupiter.

Not only was the gas giant recovering from an asteroid smash, it also underwent a… change. Jupiter lost one of its trademark stripes — a.k.a. the South Equatorial Belt (SEB) — for no apparent reason.

Although astronomers at the time theorized that there were perhaps some high-altitude clouds blocking our view of the SEB, it wasn’t until the keen infrared eyes of Keck Observatory on Mauna Kea, Hawaii, zoomed in on the planet that the SEB came into focus again.

What’s more, Jupiter’s moon Europa helped astronomers unravel the mystery as to where the belt has been hiding.

Using the Keck II telescope’s Adaptive Optics system, astronomers would normally point a powerful laser above the observatory to create a “guide star.” This artificial point of light can then be used to detect turbulence in the Earth’s atmosphere; the shimmering laser signal feeds back into the adaptive optics, allowing the telescope to slightly deform its mirror (in real-time) to compensate for the distortion.

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The result is a sharper image of an astronomical target, as atmospheric distortions can be removed from observations. It’s these same distortions that can cause stars to “twinkle” at night.

But there was a problem when observing Jupiter. As the planet is so bright, the laser guide star was overwhelmed and couldn’t be used for Jovian observations. But all was not lost, Europa was there to lend a hand and on Nov. 30, 2010, it was very bright, right next to Jupiter in the sky. Europa became the “guide star” for the adaptive optics to sense atmospheric distortions.

So, with a little help from a little moon, an amazing infrared picture of Jupiter’s inner turmoil came into focus.

Thermal infrared radiation (with a wavelength of 5 microns) was detected by Keck leaking from Jupiter’s interior. When combining the thermal radiation data with near-infrared solar radiation being reflected by the upper clouds in the Jovian atmosphere, the churning detail in the cloaked SEB was revealed (pictured top).

As the SEB slowly begins to reveal itself once more, icy clouds in the upper atmosphere gradually dissipating, only the Keck infrared telescope could cut through the Jovian atmosphere to reveal the hidden trademark stripe we’ve been missing out on for these last few months.

More information: Keck Observatory

Image credit: Mike Wong, Franck Marchis & W.M. Keck Observatory

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