"You've heard of a green flash on the sun. But a green flash on Jupiter? "I've never come across one before," says atmospheric optics expert Les Cowley. Until now, that is. Spanish astrophotographer Juan Manuel Perez Rayego captured the rare phenomenon on Dec. 26th:

"I was taking one last photo of the Great Conjunction between Jupiter and Venus, just saying goodbye," says Rayego. "Suddenly, a green fragment of Jupiter split off and floated away from the planet. It was spectacular. I've analyzed Juan's image and conclude that it is very likely a mock mirage--the same type of mirage that can create green flashes on the sun," says Cowley.

Mock mirages are caused by atmospheric temperature inversions, in which layers of air are warmer than usual. An extra 1 or 2 degrees Celsius is all it takes. Inversion layers can be quite close to ground. Indeed, Jupiter was only 1/3rd of a degree above the horizon of Arroyo de San Serván, Spain, when Rayego recorded the flash.

The low altitude of Jupiter is why the planet looked like a rainbow-colored smear when the flash occurred. The low atmosphere acts like a prism, spreading the light of stars and planets into their R-G-B components. In this wider-angle animation, Saturn may be seen as well (lower right). It too looks like a miniature rainbow, albeit without the green flash.
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Something special is happening in the sunset sky. It's a Great Conjunction of Jupiter and Saturn. The two giant planets are converging for a close encounter the likes of which have not been seen since the Middle Ages. Shahrin Ahmad of Kuala Lumpur, Malaysia, photographed the pair on Dec. 7th:

"Jupiter and Saturn are about 1.5º apart this evening, " says Ahmad. "Even under a light polluted sky, both can easily be seen."
They're about to get much closer. On Dec. 21st, the two planets will lie just 0.1 degrees apart. That's so close, some people will perceive them as a single brilliant star. Viewed through binoculars or a small telescope, ringed Saturn will appear as close to Jupiter as some of Jupiter's moons:

Although Great Conjunctions between Jupiter and Saturn occur every 20 years, they're not all easy to see. Often the two planets are hidden in the glare of the sun. This year is special because the conjunction happens comfortably away from the sun. In fact, the last time the two worlds were so close together and so easy to see was the year 1226, astronomer Michael Brown told the Washington Post.
The show is underway. Jupiter and Saturn are already a tight pair in the evening sky, and they will grow rapidly and noticeably closer together every night for the next two weeks. Dates of special interest include Dec. 16th and 17th, when the crescent Moon joins the planets, and, of course, Dec. 21st when they are almost touching. Sky maps: Dec. 16, 17; Dec. 21.
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Jupiter and Saturn will come closer to each other in the Earth's night sky than they have for almost a millennium between December 16 and 25 in an extremely rare astronomical extravaganza. The pair will be separated by one fifth the diameter of a full moon as viewed from the Earth, in an extraordinary astronomical proximity event which has not occurred for 800 years.

The planets will appear as a singular point of brilliant light or a “double planet” to anyone lucky enough to have clear skies at the time of their yuletide rendezvous

“Alignments between these two planets are rather rare, occurring once every 20 years or so, but this conjunction is exceptionally rare because of how close the planets will appear to one another,” says astronomer Patrick Hartigan from Rice University.

For context, their previous closest celestial encounter on record (as we see them anyway) was on March 4, 1226.  As always, the best viewing conditions will be near the equator but, with clear enough skies, it should be visible from anywhere on Earth about an hour after sunset each evening.  Stargazers should point their telescopes toward the western sky, especially during the closest approach on December 21, when the pair will appear as a “double planet.”

“For most telescope viewers, each planet and several of their largest moons will be visible in the same field of view that evening,” Hartigan adds.

The viewing window will be shorter for those in the northern hemisphere, however, so stargazers are encouraged to make preparations well in advance and head out early to avoid missing the mesmerizing meeting.

Their next astronomical alignment is expected in March 2080 and then again in 2400.
https://www.rt.com/news/507528-jupiter-saturn-alignment-double-planet/
Read also: https://www.iceagenow.info/jupiter-and-saturn-about-to-do-something-not-seen-since-the-year-1226/

This could be NASA's most exciting mission--ever. The space agency announced yesterday that they will send a heliocopter to Titan, Saturn's largest moon. Titan is in many ways more like Earth than any other place in the solar system. It has rivers and lakes, a thick atmosphere, and organic compounds that could support the genesis of life. The quad-chopper, named "Dragonfly," will fly between sites on interest, covering more than twice the distance of every Mars rover combined. Get the full story from nasa.gov.
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The biggest storm in the solar system is shrinking. Since mid-May, Jupiter's Great Red Spot has contracted a startling 3000 km, reducing the size of the anti-cyclone by nearly 20%.  This 10-day movie created by Marco Vedovato of the JUPOS Project shows what's happening:

Enormous rivulets of red gas are streaming away from the storm as it spins. "This is something we've never seen before," says Vedovato, who assembled the animation by stitching together images from nearly a dozen amateur astronomers.
Experienced observers say the storm is "getting a new shape every day" in a "dramatic metamorphasis" as the Red Spot "appears to be unravelling."
"The JUPOS Project manages the largest Jupiter database in the world," says Vedovato. "So far we have collected more than 1 million measurements, including old images and drawings from the 18th century, allowing us to plot very precise trends in the Great Red Spot." This plot, for instance, shows the sudden decrease in the storm's diameter since early May.

Consider it a case of perfect timing. Jupiter is about to make its annual closest approach to Earth--"only" 641 million km away on June 12th. Proximity makes the planet big and bright, shining almost four times brighter than Sirius, the brightest star in the sky. Astrophotographers are getting a fantastic view of the GRS.
Finding Jupiter is easy. Look southeast at midnight. Jupiter is located in the constellation Ophiuchus, the brightest object around: sky map.
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Awake at midnight? Go outside and look southeast. The Moon and Jupiter are having a bright conjunction in the constellation Ophiuchus, only a few degrees apart. Enjoy the show!
Sky maps: May 19, 20.
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On Oct. 26th, Venus will pass almost directly between Earth and the sun--an event astronomers call "inferior solar conjunction." As Venus approaches the sun, the planet is turning its night side toward Earth, reducing its luminous glow to a thin sliver. Shahrin Ahmad of Kuala Lumpur, Malaysia, took this picture on Oct. 20th:

"I took this picture in broad daylight," says Ahmad. "Venus was really big in the eyepiece of my telescope--almost a full arcminute in diameter. And the crescent shape easily visible in the 8x50 finder scope."
In the days ahead, the crescent of Venus will become increasingly thin and circular. The horns of the crescent might actually touch when the Venus-sun angle is least (~6 degrees) on Oct. 26th. This is arguably the most beautiful time to observe Venus, but also the most perilous. The glare of the nearby sun magnified by a telescope can damage the eyes of anyone looking through the eyepiece.
Anthony J. Cook of the Griffith Observatory has some advice for observers: "I have observed Venus at conjunction, but only from within the shadow of a building, or by adding a mask to the front end of the telescope to fully shadow the optics from direct sunlight. This is tricky with a refractor or a catadioptric, because the optics start at the front end of the tube. Here at Griffith Observatory, I rotate the telescope dome to make sure the lens of the telescope is shaded from direct sunlight, even through it means that the lens will be partially blocked when aimed at Venus. With our Newtonian telescope, I add a curved cardboard mask at the front end of the tube to shadow the primary mirror."
For the rest of this week Venus can still be observed without elaborate precautions in deep twilight after sunset. Every evening the crescent grows and narrows. Scan the realtime photo gallery for updates.
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Tonight's the night. The Moon and Mars are converging for a midnight conjunction in the constellation Capricornus. This is no ordinary meeting of heavenly bodies. Mars is making a 15-year close approach to Earth, giving the Red Planet a luminosity that pierces the glare of the full Moon with ease.

During the conjunction, something strange and wonderful will happen to the Moon. It is going to pass through the shadow of our planet, turning the lunar disk as red as Mars. Astronomers call this a "total lunar eclipse." On every continent except North America, people can see Earth's shadow swallow the Moon for as much as 1 hour 43 minutes, making it the longest lunar eclipse in a century. [eclipse visibility map]

This animation, created by graphic artist Larry Koehn, shows how the eclipse will unfold:

Got a backyard telescope? Tonight is a good time to use it. Swing your optics between the Moon and Mars in quick succession to reveal the dusty-red martian disk alongside lunar mountains and craters. It's a special night. Enjoy the show!
Live webcasts: from Israel, from Belgium.
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Friday, July 27th, is a big night for astronomy. First, Mars will be at opposition--directly opposite the sun and making a 15-year close approach to Earth. Second, Mars and the Moon will be in conjunction--less than 10 degrees apart. Third, the Moon will pass through the shadow of Earth, producing the longest lunar eclipse in a century--visible everywhere except North America. What a night! Tune into live webcasts from Israel and Belgium.
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Get out your telescope. Tonight Saturn is "at opposition"--that is, at its closest and brightest for all of 2018. To find the ringed planet, just look due south at midnight. It is easy to see with the unaided eye right beside the full Strawberry Moon in the constellation Sagittarius. [sky map]

Even a small telescope will reveal Saturn's magnificent rings. Christopher Go sends this picture taken last night from Cebu City in the Philippines:

"Saturn's rings are surging in brightness," he reports. "Now is a great time to see them."

Saturn's rings are bright near opposition in part because the rings are closer than usual to Earth. They get an additional boost from "the Seeliger Effect," named after the German astronomer Hugo van Seeliger who first described it in the 19th century. It happens when sunlit objects such as the icy particles that make up Saturn's rings hide their own shadows. Opposition is the perfect time for the Seeliger effect because Saturn and the sun are on diametrically opposite sides of the sky. A process called coherent backscattering may also contribute to the extra luminosity.

If you have a small telescope, tonight is a great time to use it. Point your optics at Saturn and enjoy the show.           www.spaceweather.com

Any night this week, step outside after midnight and look south. You'll see Jupiter, Saturn and Mars arranged in a bright line across the starry sky. The Moon can be your guide. It's hopping from one planet to the next with beautiful conjunctions on June 1st (Moon-Saturn) and especially June 3rd (Moon-Mars). Enjoy the show!
Sky maps: May 31, June 1, 2, 3, 4.     www.spaceweather.com

NASA's Cassini spacecraft captured an incredible final image of Earth from 1.4 billion km away during its orbit of Saturn's rings.  The space probe was facing Earth's Southern Atlantic Ocean, some 870 million miles (1.4 billion km) away, when the image of earth was captured on April 12, says NASA.

In a zoomed-in version of the image, Earth's moon is also clearly visible, seeming to float alongside our bright planet in the dark vastness of space.

The image marks Cassini's last view of Earth as the spacecraft prepares to end its mission by dramatically plunging into Saturn's atmosphere on September 15.  The probe's 'Grand Finale' mission begins on Friday when the spacecraft will complete a close flyby of Saturn's moon, Titan - passing a mere 600 miles above its surface - before beginning its final set of 22 orbits between Saturn and its rings.

Cassini, a $3.2 billion mission from NASA, the European Space Agency (ESA) and the Italian Space Agency, launched in 1997 and has delivered unprecedented data of Saturn and its moons.
You can see video from the mission here.

Andrew Liptak : The Verge : 16 Jan 2017

The Japanese probe Akatsuki has observed a massive gravity wave in the atmosphere of Venus. This is not the first time such a wave was observed on the Solar System's second planet, but it is the largest ever recorded, stretching just over 6,000 miles from end to end. Its features also suggest that the dynamics of Venus' atmosphere are more complex than previously thought.

An atmospheric gravity wave is a ripple in the density of a planet's atmosphere, according to the European Space Agency. (This isn't a gravitational wave, which is a ripple in space-time.) We have these waves in Earth's atmosphere, too; they interfere with weather and cause turbulence. Scientists have observed atmospheric gravity waves on Venus before: the European Space Agency's Venus Express spotted several before the end of its mission in 2014. Since its initial observations, Akatsuki has spotted several smaller structures with its infrared cameras in April and May 2016.

Akatsuki spotted this particular gravity wave, described in a paper published today in Nature Geoscience, when the probe arrived at the planet on December 7th, 2015. The spacecraft then lost sight of it on December 12th, 2015, because of a change in Akatsuki's orbit. When the probe returned to a position to observe the bow-shaped structure on January 15th, 2016, the bright wave had vanished.

What sets the huge December wave apart from previously discovered ones is that it appeared to be stationary above a mountainous region on the planet's surface, despite the background atmospheric winds.

The study's authors believe that the bright structure is the result of a gravity wave that was formed in the lower atmosphere as it flowed over the planet's mountainous terrain. It's not clear how the wave exactly propagates to the planet's upper atmosphere, where clouds rotate faster than the planets itself — four days instead of the 243 days it takes Venus to rotate once.

The massive gravity wave might mean that the atmospheric conditions closer to the planet's surface are more variable than predicted.

Venus and Jupiter are converging in the sunset sky for a close encounter on Aug.27th. Yesterday in the Snowy Mountains of NSW Australia, Phil Hart photographed the two bright planets approaching one another with Mercury looking on:

"A highlight of six days backcountry skiing in NSW was the planetary alignment of Venus, Mercury and Jupiter," says Hart. "It took a few nights to get the weather and scenery to cooperate, but after an hour of traipsing around and lying down in the snow, I managed to capture this shot on our last night out."

The view will improve in the evenings ahead as the distance between Jupiter and Venus decreases. At closest approach on Aug 27th, the two worlds will appear only about 1/15th of a degree apart. If you hold a pencil at arm's length, the eraser would cover both planets at once. Moreover, Venus and Jupiter will easily fit within a telescopic field of view--an amazing sight if you have a backyard telescope.

Remember, though, that a telescope is not required.  Venus and Jupiter are bright enough to see with the naked eye even from light-polluted urban areas. Try to catch them about 30 minutes after sunset before the sky fades completely black.  The sight of two planets in conjunction surrounded by twilight blue is extra-beautiful.
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