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Hubble Spots Jupiter Sporting a Spooky Shadow Eye

Jovian moon's shadow plays on giant storm.

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On April 21, 2014, while the Hubble Space Telescope was monitoring Jupiter's Great Red Spot, it captured the shadow of the moon Ganymede at the center of the storm.


Watch out or the cosmic cyclops will get you!

Just in time for Halloween, the Hubble Space Telescope has captured this creepy snapshot of Jupiter. (Related video: "NASA Probe to Explore Jupiter.")

What makes the planet seem to look back at us? The shadow of the moon Ganymede riding atop the clouds of the planet's immense storm called the Great Red Spot.

This amazing photo was taken by the orbiting observatory's wide-field camera back on April 21, 2014, while the space telescope was monitoring weather changes inside the red spot. But it was only released this week.

The moon's shadow "gave the giant planet the uncanny appearance of having a pupil in the center of a 10,000-mile-diameter 'eye,'" said the Hubble team in a press statement.

"Momentarily, Jupiter took on the appearance of a Cyclops planet!"

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This sky chart shows a telescope's view of Jupiter's disk in the early morning hours of Friday, November 7, just as the moon Io's shadow transits.


See for Yourself

Jupiter is easy to spot with just the naked eye as a bright starlike object rising after 1 a.m. above the northeastern horizon. By dawn it shines brightly, high in the southeastern sky.

Observe the giant planet with binoculars or a telescope, and its retinue of four major satellites, known as the Galilean moons, can be seen dancing beside it. They appear in constant motion and change positions relative to each other as they eternally revolve around the planet.

Frequently the moons' shadows can be seen transiting the cloud-tops of Jupiter, if you time your observations right.

On Friday, November 7, starting at 2:53 a.m. EST, the dotlike shadow of the moon Io will appear on the limb (edge) of Jupiter. It will take just over two hours to cross the planet's disk.

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This sky chart shows Jupiter's disk on Saturday, November 1, as the moon Ganymede's shadow eclipses its neighboring moon Io.


Disappearing Tricks

Anyone observing Jupiter through even the smallest of telescopes can, on rare occasions, watch the Jovian moons play a series of neat disappearing tricks on each other.

Over the course of the next few months, the orbital plane of Jupiter's four largest moons will happen to appear edge-on when observed from Earth. This means that the moons will appear to eclipse their neighbors when their shadows fall on each other.

On Saturday, November 1, Jupiter's largest moon, Ganymede, will eclipse the volcanically active moon Io, for example. The four-minute event begins at 4:12 a.m. EDT. Start observing before that time, and you will see the two moons side by side-slowly coming together until they appear to magically merge into one.

Amazing to witness the celestial mechanics of the solar system play out right before our eyes!

Follow Andrew Fazekas, the Night Sky Guy, on Twitter, Facebook, and his website.

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