Stunning video captures a rare Jupiter triple-eclipse: 3 large moons casting their shadows over the planet

three moons crossing jupiter circled in pink
Left to right: Europa, Ganymede, and Callisto cross in front of Jupiter, August 15, 2021.

Jupiter and its largest satellites recently performed a rare dance.

Three of the planet’s enormous moons – Europa, Ganymede, and Callisto – all paraded across Jupiter’s swirling surface at once, casting their shadows on the clouds below.

Christopher Go, an amateur astronomer in the Philippines, captured images of the spectacle around midnight on August 15. Then Kunio Sayanagi, a planetary scientist at Hampton University, compiled them into the below video.

jupiter rotating as three moons pass in front of it casting shadows on jupiter

Each second of the video represents 30 minutes of real time.

“I already knew what was going to happen, but seeing it live was surreal,” Go told Insider.

In a blog post, he said he’d been waiting for this “grand slam event” all year.

From the surface of Jupiter, the area that falls in shadows of these moons would see a solar eclipse. But from Earth, this occurrence is called a “transit,” since as the moons pass between us and Jupiter, they’re transiting the giant planet. Transits are common on Jupiter – several hundred happen each year. But it’s rare for three to occur at once. The last time a triple transit happened was in 2015, according to Sayanagi, and the next one won’t happen again until 2032.

“This is a very difficult data to capture,” Sayanagi told Insider. “I am convinced that this is the best movie ever made of Jupiter’s triple transit event.”

Go was especially lucky to capture this footage, since it’s the middle of monsoon season in the Philippines. It rained every night the week of the triple transit, but the skies cleared just in time for Go to prepare his telescope and watch the Jovian trio parade across the planet’s bands.

One moon briefly eclipses the other

There’s more to this video than the triple transit, though. At the beginning, the yellow-hued moon Io makes a brief appearance as it zips behind Jupiter. Then about halfway through, something more unusual happens: Europa passes between Ganymede and Jupiter.

Europa, a small icy world with an ocean deep below its surface, briefly disappears behind the larger Ganymede. As it reemerges, Ganymede’s shadow is visibly eclipsing the little moon.

jupiter moons transiting with pink arrow pointing to europa with ganymede's shadow
Europa (right) emerges from behind Ganymede (left) with the larger moon’s shadow eclipsing it.

“That was really exciting was to see the shadow of Ganymede split,” Go said. “Half on Europa and the other half on the surface of Jupiter.”

Ganymede is the largest moon in the solar system and has its own hidden ocean, just like Europa. Many scientists think these moons’ subsurface oceans could host alien life.

Galileo Galilei first observed the four moons in this video – Europa, Ganymede, Callisto, and Io – in 1610. It was the first time anybody had documented objects orbiting another planet. That got Galileo thinking that maybe Earth wasn’t the center of the universe.

“We all know that today, but even then, seeing the moons dance around Jupiter casting shadows and eclipsing each other is awe-inspiring,” Sayanagi said.

In total, scientists think Jupiter has 79 moons, but the rest of them are much smaller than the four Galilean moons.

Europa
Europa, as imaged by NASA’s Galileo spacecraft in the late 1990s.

Even without its moons, Jupiter’s colorful clouds and raging storms make for a stunning astronomical sight.

“I have been observing Jupiter whenever I can since 2003,” said Go, who runs a furniture company with his wife. “Jupiter is so dynamic that you can see changes everyday.”

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A mesmerizing NASA video lets you ride with the Juno spacecraft as it flies by Jupiter and its largest moon

NASA's Juno spacecraft in orbit above JupiterÕs Great Red Spot is seen in this undated handout illustration obtained by Reuters July 11, 2017.  NASA/JPL-Caltech/Handout via REUTERS
An illustration of NASA’s Juno spacecraft in orbit around Jupiter.

NASA’s Juno spacecraft has been beaming photos of Jupiter back to Earth since 2016, but a new video shows what the view might look like from inside the probe as it flies past Jupiter’s roaring cyclones and giant storms.

The footage also offers a front-row look at Jupiter’s largest moon, Ganymede – an icy orb larger than Mercury.

Juno flew within 645 miles of Ganymede last week – the closest any spacecraft has gotten to the moon in more than two decades. (The last approach was by NASA’s Galileo spacecraft in 2000.) Less than a day later, Juno conducted its 34th flyby of Jupiter, snapping photos along the way.

Citizen scientist Gerald Eichstädt compiled images from both of those journeys into a time-lapse video that shows what it’s like to pass by the celestial bodies. The video lasts three minutes and 30 seconds, but in reality, it took Juno nearly 15 hours to travel the 735,000 miles between Ganymede and Jupiter, then about three additional hours to travel between Jupiter’s poles.

Take a look at the video below:

The beginning of the footage reveals Ganymede’s cratered surface, marked by dark patches that likely form as ice changes directly from solid to gas. If you look closely, you can see one of Ganymede’s largest and brightest craters, Tros, surrounded by white rays of ejected material.

When it captured those images, Juno was traveling at a speed of roughly 41,600 miles per hour. But as the spacecraft got closer to Jupiter, it picked up speed: The planet’s gravity accelerates Juno to nearly 130,000 miles per hour during its flybys.

The video shows Jupiter’s turbulent surface emerging from the dark abyss of space like a watercolor painting. White ovals indicate a set of giant storms in Jupiter’s southern hemisphere known as the “string of pearls.” (There are five of them in the video.) Flashes of white light represent lightning.

“The animation shows just how beautiful deep-space exploration can be,” Scott Bolton, Juno’s principal investigator at the Southwest Research Institute in San Antonio, Texas, said in a statement.

He added: “Today, as we approach the exciting prospect of humans being able to visit space in orbit around Earth, this propels our imagination decades into the future, when humans will be visiting the alien worlds in our solar system.”

Juno has already solved some of Jupiter’s mysteries

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Jupiter.

Juno flies in an elliptical orbit around Jupiter, getting close to the planet once every 53 days. Its recent close pass to Ganymede, however, shortened that orbit to 43 days.

The spacecraft’s main goal is to gain insight into Jupiter’s origins and evolution by mapping its magnetic fields, studying its northern and southern lights (or auroras), and measuring elements of its atmosphere – including temperature, cloud movement, and water concentrations.

The spacecraft entered Jupiter’s orbit in July 2016. (Jupiter is roughly 390 million miles away from Earth.) Its mission was initially supposed to end this month, but NASA has extended Juno’s lifespan through 2025.

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Jupiter as seen by the Juno probe during its 10th flyby.

Juno’s previous flybys have yielded important discoveries, like the fact that most of Jupiter’s lightning is concentrated at its north pole. The spacecraft also found that storms tend to appear in symmetrical clusters at Jupiter’s poles, and that the planet’s powerful auroras produce ultraviolet light that’s invisible to human eyes.

Just this week, Juno’s measurements helped scientists figure out why these auroras form in the first place: Electrically charged atoms, or ions, “surf” electromagnetic waves in Jupiter’s magnetic field before crashing into the planet’s atmosphere.

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NASA’s Juno probe at Jupiter beamed back close-up photos of the planet’s largest moon, Ganymede, for the first time in 2 decades

nasa juno spacecraft ganymede flyby thumbnail
The Juno spacecraft (left) flew past Ganymede (right) on Monday.

Grey, heavily cratered, and peering out from the black of space, Ganymede looks a lot like our moon. But the icy rock is more than 400 million miles away – it’s the largest moon in the solar system, and it circles Jupiter.

NASA’s Juno spacecraft has been rocketing around Jupiter since 2016, but on Monday, it zipped past Ganymede, coming within 645 miles of the moon. No spacecraft had gotten that close in more than two decades – the last approach was NASA’s Galileo spacecraft in 2000.

In just 25 minutes, Ganymede went from being a distant point of light from Juno’s vantage point to a looming, round disk, then back to a point of light. It was just enough time for the probe to snap five photos.

NASA released the first two images on Tuesday; they’re the most detailed snapshots ever captured of the gargantuan moon.

“This is the closest any spacecraft has come to this mammoth moon in a generation,” Scott Bolton, who leads the Juno spacecraft team, said in NASA’s press release. “We are going to take our time before we draw any scientific conclusions, but until then we can simply marvel at this celestial wonder – the only moon in our solar system bigger than the planet Mercury.”

Scientists believe that Ganymede may host an ocean of salty water 500 miles beneath its icy shell – which would hold more water than Earth does. It’s also the only moon in the solar system with its own magnetic field, which creates an aurora at its poles. Scientists hope the Juno flyby will help them learn more about both Ganymede’s ice shell and its magnetic field.

The first Juno image, below, captures almost an entire side of the ice-encrusted moon. Each pixel covers about 0.6 miles (1 kilometer).

ganymede jupiter moon juno photo close up
This image of Ganymede was obtained by the JunoCam imager during Juno’s June 7, 2021 flyby of the icy moon.

This image is just from the Juno camera’s green-light filter. In the coming days, NASA expects to receive more images from the spacecraft, including those captured with its red- and blue-light filters. That will allow the agency to create a colorful portrait of Ganymede.

Juno’s black-and-white navigation camera also snapped a photo, below, of Ganymede’s dark side.

ganymede jupiter moon surface up close juno flyby
This image of the dark side of Ganymede was obtained by Juno’s Stellar Reference Unit navigation camera during its June 7, 2021 flyby.

It’s visible thanks to light scattered from Jupiter.

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