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This video is a globe map of the distant planet Neptune, created from The Hubble Space Telescope data taken on January 7 and 8, 2020.
The film reveals Neptune’s dynamic weather: white clouds of methane ice crystals swirling around the planet and two giant dark spots in the northern hemisphere. The biggest spot, a giant storm, resides at the top of the planet; the smallest place, is located below and to the right of its larger cousin. The planet rotates every 16 hours.
Around the South Pole, the banding is concentrated where the winds blow from west to east, in the same direction as the rotation of the planet. Closer to the equator, including where the dark vortex is, the winds blow from east to west, in the opposite direction of the planet’s rotation.
The giant vortex is 4,600 miles in diameter, larger than the Atlantic Ocean. The slightly smaller companion is 3,900 miles in diameter. The smallest feature may be a spin-off of the giant storm that then vanished.
Credit: NASA, ESA, MH Wong (University of California, Berkeley), LA Sromovsky and PM Fry (University of Wisconsin-Madison), and J. DePasquale (STScI)
When NASA’s Voyager 2 spacecraft flew over Neptune in 1989 after an odyssey of nearly 3 billion kilometers, astronomers expected to observe a blue-green planet up close that seemed as devoid of features as a marble. Instead, they were shocked and intrigued to see a vibrant, turbulent world of swirling storms, including a giant feature dubbed the Great Dark Spot, looming in Neptune’s southern hemisphere.
The vortex recalled JupiterThe legendary Great Red Spot, a monstrous storm that has raged for hundreds of years. Had this great dark spot been brewing for the same amount of time? Or was it a more fleeting storm?
Scientists must have waited until 1994, when the Hubble Space Telescope and its sharp vision scanned Neptune in the distance. The mysterious place had disappeared! This planetary peek-a-boo game continued when Hubble spotted another dark storm appearing in Neptune’s northern hemisphere in 1995. Over the past three decades, Hubble has continued to observe the planet, looking at several more dark spots come and go.
Only Hubble can study these spots because it has the clear vision to observe them in visible light. Hubble has shown that these storms live for a few years before disappearing or disappearing.
Researchers believed the current giant storm in the northern hemisphere was heading for destruction when it mysteriously interrupted its journey south and began to drift north. Along with the stunning spot reversal, a new, slightly smaller dark line appeared near its larger cousin and then vanished. These surprising events add to the mystery of this dynamic world.
Astronomers using NASA’s Hubble Space Telescope have observed a mysterious dark vortex over Neptune abruptly pull away from probable death on the giant blue planet.
The storm, which is larger than the Atlantic Ocean, originated in the planet’s northern hemisphere and discovered by Hubble in 2018. Observations a year later showed it began to drift south toward the equator, where such storms are expected to disappear from view. To the surprise of observers, Hubble spotted the change in direction of the vortex in August 2020, doubling north. Although Hubble has followed similar dark spots for the past 30 years, this unpredictable atmospheric behavior is something new to see.
Equally confusing, the storm was not the only one. Hubble spotted another smaller dark spot in January of this year that temporarily appeared near its larger cousin. It may be a piece of the giant vortex that broke apart, moved away, and then disappeared in later observations.
“We are excited about these observations because this smaller dark fragment is potentially part of the dark spot disruption process,” said Michael H. Wong of the University of California, Berkeley. “It’s a process that has never been observed. We’ve seen other dark spots fade away, and they’re gone, but we’ve never seen anything disruptive, even though it’s predicted in computer simulations.
This Hubble Space Telescope snapshot of the dynamic blue-green planet Neptune reveals a monstrous dark storm (top center) and the emergence of a smaller dark spot nearby (top right). The giant vortex, which is larger than the Atlantic Ocean, was heading south toward a certain destiny by atmospheric forces at the equator when it suddenly turned around and began to drift north. Credit: NASA, ESA, STScI, MH Wong (University of California, Berkeley), and LA Sromovsky and PM Fry (University of Wisconsin-Madison)
The great storm, which measures 4,600 miles in diameter, is the fourth dark spot that Hubble has observed on Neptune since 1993. Two more dark storms were discovered by the Voyager 2 spacecraft in 1989 as it flew near the distant planet , but they were gone before Hubble could observe them. Since then, only Hubble has had the sharpness and sensitivity to visible light to keep up with these elusive features, which appeared sequentially and then faded over a span of about two years each. Hubble discovered this latest storm in September 2018.
Bad weather
Neptune’s dark vortices are high pressure systems that can form at mid-latitudes and then migrate toward the equator. They begin by remaining stable due to Coriolis forces, which cause storms in the northern hemisphere to rotate clockwise, due to the planet’s rotation. (These storms are different from hurricanes on Earth, which rotate counterclockwise because they are low pressure systems.) However, as a storm drifts towards the equator, the Coriolis effect weakens and the storm disintegrates. In the computer simulations of several different teams, these storms follow a more or less rectilinear trajectory towards the equator, until there is no longer the Coriolis effect to hold them together. Unlike simulations, the last giant storm did not migrate to the equatorial “destruction zone”.
“It was really exciting to see this one act like he’s supposed to act and then all of a sudden he stops and goes back,” Wong said. “It was surprising.
Dark Spot Jr.
Hubble’s observations also revealed that the puzzling dark vortex path reversal occurred at the same time as a new spot, unofficially referred to as the ‘dark spot jr’, appeared. The most recent spot was slightly smaller than its cousin, measuring about 3,900 miles in diameter. It was near the side of the main dark spot that faces the equator – the place where some simulations show a disturbance would occur.
The smallest dark spot in this Hubble image may have been a piece of the giant storm that ruptured as the larger vortex approached the equator. Hubble discovered the giant storm in September 2018 in Neptune’s northern hemisphere. The large feature measures approximately 4,600 miles in diameter. The estimated width of the smallest spot is 3,900 miles. Credit: NASA, ESA, STScI, MH Wong (University of California, Berkeley), and LA Sromovsky and PM Fry (University of Wisconsin-Madison)
However, the timing of the emergence of the smaller spot was unusual. “When I first saw the little spot, I thought the bigger one was upset,” Wong said. “I didn’t think another vortex was forming because the little one is further from the equator. So it is in this unstable region. But we cannot prove that the two are related. It remains a complete mystery.
“It was also in January that the dark vortex stopped moving and started moving north again,” Wong added. “Perhaps erasing that fragment was enough to keep it from moving towards the equator.
Researchers continue to analyze more data to determine whether the remains of Dark Spot jr. persisted for the remainder of 2020.
Dark storms always confusing
How these storms form remains a mystery, but this latest giant black vortex is the best studied to date. The storm’s dark appearance may be due to a high dark cloud layer and could inform astronomers of the vertical structure of the storm.
Another unusual feature of the dark spot is the absence of bright companion clouds around it, which were present in the Hubble images taken when the vortex was discovered in 2018. Apparently, the clouds disappeared when the vortex has interrupted its journey south. Bright clouds form when airflow is disturbed and diverted upward above the vortex, likely causing the gases to freeze into methane crystals. The lack of clouds could reveal information about how the spots are changing, the researchers say.
Weather Eye on the outer planets
Hubble has taken numerous images of the Dark Spots as part of the Outer Planet Atmospheres Legacy (OPAL) program, a long-term Hubble project, led by Amy Simon of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, which captures annually world maps. of the outer planets of our solar system when they are closest to Earth in their orbit.
The main goals of OPAL are to study long-term seasonal changes, as well as to capture relatively transient events, such as the appearance of dark spots on Neptune or potentially Uranus. These dark storms can be so fleeting that in the past some of them may have appeared and faded for intervals of several years in Hubble’s observations of Neptune. The OPAL program ensures that astronomers won’t miss another.
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