Category Archives: Jupiter

Eppur Si Muove: Galileo’s Big Night

Note: This is an edited repost of an article from 2014.
Jupiter and the fours "Galilean moons" Europa, Io, Callisto, and Ganymede. (Jan Sandberg/

Jupiter and the four “Galilean moons” Europa, Io, Callisto, and Ganymede. (Jan Sandberg/

405 years ago tonight, January 7, 1610, the Pisan astronomer Galileo Galilei looked up at a bright Jupiter at opposition through his handmade telescope and saw three little “stars” next to it, which piqued his natural scientific curiosity. He soon realized that these little objects weren’t stars at all but rather moons orbiting the giant planet (and, most importantly, not Earth). Further observations over the next few nights showed that the planet wasn’t moving relative to the little “stars” as it should if they were indeed background stars, and in fact the smaller bodies (of which he soon saw four) were moving along with Jupiter each in its own little orbit. This revelation helped change our entire view of the Solar System, causing no end of trouble for Galileo (as the Church didn’t appreciate data contradicting their conveniently Earth-centered Universe) but also opening the door for the discovery of many more moons around other planets.

Today Jupiter is now known to have at least 50 moons, with possibly as many as 67!

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Jupiter’s Moons Make Ghostly Auroral “Footprints”

UV image of Jupiter taken with the Hubble Space Telescope Imaging Spectrograph (STIS) on November 26, 1998. (NASA/ESA, John Clarke (University of Michigan))

Aurorae seen in a UV image of Jupiter taken with the Hubble Space Telescope Imaging Spectrograph (STIS) on November 26, 1998. (Credit: NASA and the Hubble Heritage Team)

We have all marveled at incredible photos and time-lapse videos of Earth’s auroral displays, captured by talented photographers that have braved the frigid nighttime temperatures of remote high-latitude locations as well as by those privileged few living in orbit aboard the International Space Station. But our planet isn’t the only one with curtains of light crowning its poles – aurorae have been observed on Jupiter, Saturn, Uranus, and Neptune as well (and Venus may even have them too.) While we know that these light shows are caused by interactions between atoms in planets’ upper atmospheres and charged particles from the Sun that get caught up in magnetic fields focusing out from around the poles, Jupiter in particular is known to have a peculiar additional type of auroral feature, created by the moons that orbit it.

The image above, captured by the Hubble Space Telescope Imaging Spectrograph (STIS) on November 26, 1998, shows Jupiter’s north polar region in ultraviolet light. The planet’s energetic aurorae can be seen wrapping around its pole in wavy circular arcs, just like Earth’s does. But there are also several bright spots that aren’t due to solar activity but are instead the “footprints” of three of its largest moons: Ganymede, Europa, and Io.

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An Ocean Beyond Earth: Europa Awaits

It’s no secret that Earth’s ocean is filled with life, much of it still a mystery or totally unknown to science. But what about the ocean on other worlds? I’m not talking about sci-fi planets or suspected alien Earths around other stars, but right here in our own solar system, where an ocean even deeper than ours lies hidden beneath a global shell of ice.

Scientists believe there is an ocean hidden beneath the surface of Jupiter’s moon Europa. In the video above, NASA-JPL astrobiologist Kevin Hand explains why scientists are so excited about the potential of this ice-covered world to answer one of humanity’s most profound questions: does life exist beyond Earth?

To learn more about Europa click here, and see the latest enhanced version of a Galileo image of Europa below:

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Dear Jupiter: Use More Sunscreen

Image of Jupiter's Great Red Spot from Voyager 1, 1979 data. Edited by Björn Jónsson.

Image of Jupiter’s Great Red Spot from Voyager 1, 1979 data. Edited by Björn Jónsson.

It’s the signature accessory of the largest planet in our solar system: Jupiter’s Great Red Spot, an enormous anticyclone over twice the width of our entire planet. Visible in even modest backyard telescopes, the GRS has been churning away for at least several hundred years. But, based on recent analysis of data gathered by the Cassini spacecraft during its pass by Jupiter in December 2000, the Great Red Spot’s rusty coloration may actually only be skin-deep – a “sunburn” created by interaction between Jupiter’s upper atmosphere and solar radiation.

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Boom! Io Explodes With Volcanic Eruptions Hundreds of Miles High

A volcanic outburst on Io on Aug. 29, 2013. Credit: Katherine de Kleer/UC Berkeley/Gemini Observatory

Infrared image of a volcanic outburst on Io on Aug. 29, 2013. Credit: Katherine de Kleer/UC Berkeley/Gemini Observatory

Three enormous volcanic eruptions on Jupiter’s moon Io were witnessed by scientists last year using the Keck II and Gemini telescopes in Hawaii. The only other confirmed volcanically-active world in the solar system besides Earth, Io is constantly being resurfaced by eruptions and lava flows, due to internal heat and pressures caused by tidal stresses as a result of its elliptical orbit around Jupiter. These recent outbursts were exceptionally powerful, sending huge amounts of incredibly hot molten material out into space and likely coating a large area on its surface as well.

“We typically expect one huge outburst every one or two years, and they’re usually not this bright,” said Imke de Pater, professor and chair of astronomy at UC Berkeley and lead author of a paper describing the 2013 eruptions. “Here we had three extremely bright outbursts, which suggest that if we looked more frequently we might see many more of them on Io.”

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Europa Is Covered In Bacon. That Is Why We Must Go.

A newly-released image of Europa's surface captured by Galileo (NASA/JPL)

A newly-released image of Europa’s surface captured by Galileo (NASA/JPL)

Whether you’re a trend-loving hipster, a breakfast lover, or just fan of meat products in general, you’d have to agree that it does look like a giant piece of bacon* running across the image above. And while the color and shape seems about right, the size and temperature is a bit off — that’d be a piece of fried pork 25 miles wide and -300ºF!

All kidding aside, this is actually a newly-released picture of the frozen surface of Jupiter’s moon Europa, made from images acquired by NASA’s Galileo spacecraft in 1997 and 1998. The dark coloration of the river-like bands is thought to be the result of organic compounds staining the water ice that has welled up from the moon’s deep subsurface ocean… all the more reason that yes, we really should attempt a landing there in the very near future!

Read more about this in my article on Universe Today here.

*No pigs were harmed in the production of this image.


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