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Hubble shows the atmospheres of Uranus and Neptune

Like the earth, Uranus and Neptune have the season and experience changes in weather patterns as a result. But unlike the earth, the seasons on these planets last for years instead of months and weather patterns take place on a scale that is unthinkable according to the standards of the earth. A good example are the storms that have been observed in the atmosphere of Neptune and Uranus, including the famous Great Dark Spot of Neptune.

During his annual routine of monitoring Uranus and Neptune, NASA & # 39; s Hubble space telescope (HST) recently provided updated observations of the weather patterns of both planets. In addition to finding a new and mysterious storm on Neptune, Hubble provided a fresh look at a long-lived storm around the north pole of Uranus. These observations are part of HubbleThe long-term mission to improve our understanding of the outer planets.

The new images were created as part of the Outer Planet Atmospheres Legacy (OPAL) program, a long-term vision Hubble project led by Amy Simon from NASA's Goddard Space Flight Center. Every year this program captures global maps of the outer planets of our solar system when they are closest to the earth. One of the main goals of OPAL is to study seasonal changes in the long term and relatively transient events, such as the appearance of dark spots.

Voyager 2 captured this image of Neptune in 1982, when it was more than 7 million km (4.4 million miles) away from the planet. The Great Dark Spot in the middle of the image was the first storm ever seen on Neptune. Credit: by NASA-JPL

It is no easy task to spot them, because these dark spots appear quickly and live relatively briefly, to the point where some have appeared and disappeared during multi-year gaps in Hubble's observations of Neptune. This is another goal of the OPAL program, namely to ensure that astronomers do not miss any other.

This last dark spot, measuring approximately 11,000 km (6,800 miles) in diameter, appears at the top in the middle of the planet. Hubble discovered it for the first time in September 2018, when the southern hemisphere of Neptune passed through the summer. This is in line with the seasonal change on the planet, where warming in the southern hemisphere causes the weather patterns to become more dramatic in the north.

Although it is unclear exactly how these storms have formed, new research by Simon and the OPAL team indicate that they are fast-moving, lasting four to six years and then disappearing over the course of two years. Like the Great Red Spot of Jupiter, the dark vertebrae swirl in an anti-cyclonal direction and seem to dredge material from deeper layers into the atmosphere of the ice giant.

In fact, Hubble observations obtained since 2016 seem to indicate that the vertebrae are likely to develop deeper into the Neptune's atmosphere and become visible only when the top of the storm reaches higher altitudes. In the meantime they are accompanied by "companion clouds", which are visible in the Hubble images as bright white spots to the right of the dark function.

This Hubble Space Telescope Wide Field Camera 3-image of Neptune, made in September and November 2018, shows a new dark storm (top center). Credit: NASA, ESA / A Simon (NASA Goddard Space Flight Center), and M. Wong and A. Hsu (University of California, Berkeley)

These clouds consist of methane ice that freeze when the swirls cause the airflow to be drained upwards over the storm. The long, thin cloud to the left of the dark spot is a temporary feature that is not part of the storm system. The same goes for Uranus, which shows a huge clear cloud cover over the North Pole.

In the case of Uranus, scientists believe that this is due to the unique orientation of Uranus, where its axis is tilted by more than 90 ° with respect to the Sun's equator. Because Uranus runs practically on its side, the sun shines almost directly on the North Pole during the summer in the northern hemisphere. At this time Uranus is approaching the middle of its summer season, making the pool cap area more prominent.

This polar cap can be the result of seasonal changes in the atmospheric current and is accompanied by a large, compact methane ice cloud near the edge in the image. Also visible is a narrow cloud band that circles the planet north of the equator. This is another mystery about Uranus and Neptune, that is how bands like these are limited to such narrow latitudes as the planet has such wide, west-facing windbeams.

This is the fourth mysterious vortex that Hubble has been proposing since 1993 and the sixth since astronomers first became aware of these phenomena. The first two dark spots were discovered by the Voyager 2 spacecraft as it made its historic flight from Neptune in 1989. Since then, only the Hubble space telescope has been able to follow these functions due to the sensitivity to blue light.

This Hubble Space Telescope Wide Field Camera 3 image of Uranus, made in November 2018, reveals a huge bright stormy cloud cover over the planet's North Pole. Credit: NASA / ESA / A Simon (NASA Goddard Space Flight Center), and M. Wong and A. Hsu (University of California, Berkeley)

These images are part of a growing database of Hubble snapshots of Neptune and Uranus that follow the planet's weather patterns over time. Just as meteorologists predict the weather on Earth on the basis of long-term trends, astronomers hope that Hubble's long-term surveillance of the outer planets will help unravel the persistent mysteries of their spheres.

Analyzing the weather on these worlds will also improve our understanding of the diversity of atmospheres in the solar system, as well as their similarities. Ultimately, this could also go a long way towards informing our understanding of extrasolar planets and their spheres, perhaps even helping us determine if they can sustain life.

Read more: Hubblesite

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