Like the Earth, Uranus and Neptune have a season and are trying to change their weather patterns. But unlike Earth, the seasons of these planets continue for years, not months, and meteorological patterns occur on a scale unimaginable to Earth standards. A good example is the storms observed in the atmosphere of Neptune and Uranus, which include the famous Great Dark Spot of Neptune.
During his annual Uranus and Neptune Observing Practice, NASA Hubble Space Telescope (HST) recently provided topical observations of the models of the two planets. Besides seeing a new and mysterious storm of Neptune, Hubble gives a new look to a long-lived storm around Uranus' North Pole. These observations are part of HubbleLong-term mission to improve our understanding of the outer planets.
The new images were made as part of the OPAL, long-term Hubble a project led by Amy Simon from NASA's Space Flight Center. Every year, this program captures global maps of the outer planets of the Solar System when they are closest to Earth. One of OPAL's main goals is to explore long-term seasonal changes and relatively transient events such as the appearance of dark spots.
They are not an easy task, as these dark spots appear quickly and are relatively short-lived, to the point where some may have appeared and disappeared during the many years of Hubble Observations of Neptune. This is another goal of the OPAL program, which must ensure that astronomers do not miss another.
This last dark spot, which is approximately 11,000 km in diameter, appears in the upper center of the planet. Hubble was first seen in September 2018, when Neptune's southern hemisphere experienced summer. This is in line with the seasonal change of the planet, where warming in the southern hemisphere causes more dramatic weather patterns to the north.
Although it is unclear how these storms are formed, Simon's new research and OPAL team show that they are rapidly formed, continue for four to six years, and then disappear for two years. Like the Red Spot of Jupiter, the dark whirlwinds revolve in an anticyclonic direction and seem to raise material from deeper levels into the atmosphere of the ice giant.
In fact, Hubble's observations from 2016 show that the whirlwinds are likely to deeper into the atmosphere of Neptune and only become visible when the storm reaches higher heights. At the same time, they are accompanied by "cloud satellites" seen in Hubble's images as bright white spots to the right of the dark function.
These clouds consist of methane ice, which freezes when vortices cause deviation of the flow of ambient air upstream of the storm. The long, thin cloud to the left of the dark spot is a transient characteristic that is not part of the storm. The same is true of Uranus, which shows a huge bright cloud cover on the North Pole.
In the case of Uranus, scientists believe that this is the result of Uranus' unique orientation, where its axis is tilted over 90 ° to the solar equator. Since Uranus is traveling almost on its own side, the Sun shines almost directly at the North Pole in summer in the northern hemisphere. Uranus is now approaching the middle of its summer season, making the polar hats region more visible.
This polar hat may be the result of seasonal changes in the atmospheric flow and is accompanied by a large, compact cloud of methane-ice near its edge in the image. There is also a narrow cloud strip that surrounds the planet north of the equator. This is another mystery about Uranus and Neptune, which such bands are limited to such narrow latitudes as the planet has such great wind jets in the west.
This is the fourth mysterious vortex depicted by Hubble in 1993 and the sixth since astronomers first realized these phenomena. The first two dark spots were discovered by Voyager 2 spacecraft since he made his historic flight to Neptune in 1989 Hubble Space Telescope is able to monitor these characteristics due to their sensitivity to blue light.
These images are part of the growing database of Hubble's images of Neptune and Uranus that track the weather patterns of the planet over time. Similar to how meteorologists predict Earth time based on long-term trends, astronomers hope that long-term monitoring of the outer planets will help Hubble to uncover the lasting mysteries of their atmosphere.
The analysis of time in these worlds will also improve our understanding of the diversity of atmospheres in the solar system as well as their similarities. Ultimately, this could do much to inform our understanding of exoplanets and their atmospheres, maybe even help us determine if they can support life.
Additional Reading: Hubblesite