Hubble’s stunning grand tour of the outer solar system

Credit: NASA, ESA, Amy Simon (NASA-GSFC), Michael H. Wong (UC Berkeley). Joseph DePasquale (STScI)

Stunning annual observations reveal changes in gas giant atmosphere

In Greek mythology, a race of giants, called the Titans, first ruled the world. The ancient Titans of the solar system are the outer planets:[{” attribute=””>Jupiter, Saturn, " data-gt-translate-attributes="[{" attribute="">Uranus, and Neptune. The inner planets, Mercury, " data-gt-translate-attributes="[{" attribute="">Venus, Earth, and " data-gt-translate-attributes="[{" attribute="">Mars, huddling close to the warm Sun, are pebbles by comparison. Stretching from 500 million to 3 billion miles from the Sun, these monsters are as remote as they are mysterious, dwelling so far from the Sun that water instantly freezes to solid ice. These so-called gas giants all have deep swirling atmospheres made up mostly of primordial elements. They do not have solid surfaces.

In the 1970s and 1980s, " data-gt-translate-attributes="[{" attribute="">NASA’s Pioneer 10 and 11, and Voyager 1 and 2, first made the long-distance trek to the outer solar system. They gave humankind dazzling close-up photos of these remarkably complex worlds. In the 1990s along came the Hubble Space Telescope to pick up where these interplanetary pathfinders left off. Annually, Hubble monitors changes in the colorful swirling atmosphere of Jupiter, seasonal storms coming and going on Saturn and Uranus, and a wandering dark spot that plays peek-a-boo on Neptune. As the solar system’s weatherman, Hubble’s ultra-sharp monitoring of these magnificent giants keeps giving astronomers insights into an ever-changing kaleidoscope of weather on other worlds.

From its vantage point above Earth’s atmosphere, NASA’s Hubble Space Telescope completed its grand tour of the outer solar system this year, returning crisp images that complement current and past observations from interplanetary spacecraft. It is the realm of giant planets – Jupiter, Saturn, Uranus and Neptune – extending up to 30 times the distance between Earth and the Sun.

Unlike rocky terrestrial planets like Earth and Mars that huddle close to the warmth of the Sun, these distant worlds are mostly composed of cold gaseous soups of hydrogen, helium, ammonia, methane and deep water around of a compact, intensely hot core. .

Although robotic spacecraft have sent back snapshots of their visits to these four massive planets over the past 50 years, their swirling, colorful atmospheres are constantly changing. While robotic spacecraft flying near planets can take sharper images, Hubble frequently revisits these distant worlds to reveal new surprises, offering new insights into their savage climate, driven by still largely unknown dynamic forces working beneath them. cloud tops.

Grand Tour of OPAL

From its vantage point above Earth’s atmosphere, NASA’s Hubble Space Telescope completed its grand tour of the outer solar system – Jupiter, Saturn, Uranus and Neptune – this year returning crisp images that complement current observations. and past interplanetary spacecraft. Credit: NASA, ESA, Amy Simon (NASA-GSFC), Michael H. Wong (UC Berkeley). Joseph DePasquale (STScI)

Hubble snapshots of the outer planets reveal both extreme and subtle shifts rapidly occurring in these distant worlds. Hubble’s sharp view gleans information about the fascinating and dynamic weather patterns and seasons of these gas giants and allows astronomers to investigate the very similar – and very different – ​​causes of their changing atmospheres.

These Hubble images are part of the annual maps of each planet taken as part of the Outer Planets Atmospheres Legacy, or OPAL, program. The program provides annual global views of the outer planets to look for changes in their storms, winds and clouds. Hubble’s longevity and unique vantage point have given astronomers a unique chance to check the outer planets on an annual basis. The knowledge of the OPAL program can also be extended far beyond our own solar system in the study of the atmospheres of planets that orbit stars other than our Sun.

Hubble Jupiter 2021

Images of Jupiter taken by Hubble in 2021 trace the ever-changing landscape of its turbulent atmosphere, where several new storms are making their mark. Credit: NASA, ESA, A. Simon (NASA-GSFC) and MH Wong (UC Berkeley); Image processing: J. DePasquale (STScI)

Jupiter

This year’s Hubble images of Jupiter track the ever-changing landscape of its turbulent atmosphere, where several new storms are making their mark, and the pace of color changes near the planet’s equator continues to surprise researchers.

Hubble’s September 4and photo showcases the tumultuous atmosphere of the giant planet.

The equatorial zone of the planet remained a deep orange hue for much longer, compared to previous episodes of dimming. While the equator has changed from its traditional white or tan appearance for a few years now, scientists were surprised to find that the deeper orange color persists in recent Hubble imagery, instead expecting the area loses its layer of reddish haze.

Just above the equator, researchers note the appearance of several new storms, nicknamed “barges” during the Voyager era. These elongated red blood cells can be defined as cyclonic vortices, which vary in appearance. While some of the storms are sharply defined and clear, others are blurry and hazy. This difference in appearance is caused by the properties within the vortex clouds.

“Every time we get new data, the image quality and detail of cloud features always blows my mind,” said Amy Simon of Goddard Space Flight Center in Greenbelt, Maryland. “It strikes me when I look at Jupiter, in the barges or in the red band just below, you can see cloud structures that are clearly much deeper. We see a lot of structure here and vertical variations in depth.

The researchers also note that a feature dubbed “Red Spot Jr.” (Oval BA), below the Great Red Spot, where Hubble just discovered the winds are picking up, is still a darker beige color and is joined by a chain of white high-pressure storms to the south.

Hubble Saturn 2021

Hubble’s look at Saturn in 2021 shows rapid and extreme color shifts in the planet’s northern hemisphere bands. Credit: NASA, ESA, A. Simon (NASA-GSFC) and MH Wong (UC Berkeley); Image processing: A. Pagan (STScI)

Saturn

Hubble’s new look at Saturn on September 12and shows rapid and extreme color changes of the bands in the planet’s northern hemisphere, where it is now early fall. The bands have varied throughout Hubble’s observations in 2019 and 2020. Notably, Saturn’s iconic hexagonal storm, first discovered in 1981 by the Voyager 2 spacecraft, was difficult to distinguish in 2020, but is at again clearly evident in 2021. Hubble’s image of Saturn captures the planet after the Southern Hemisphere’s winter, evident in the lingering bluish tint of the South Pole. In the past, Hubble has allowed researchers to closely track seasonal changes in the Northern Hemisphere.

“That’s something we can do better with Hubble. With Hubble’s high resolution, we can cut things down to the tape that actually changes,” said Michael Wong of the University of California, Berkeley. “If you were to look at this through a telescope on the ground, there’s a bit of blurring in our atmosphere, and you’ll lose some of those color variations. Nothing from the ground will get visible light images as sharp as those of Hubble.

Hubble Uranus 2021

Hubble’s 2021 view of Uranus imaged the planet’s northern hemisphere during its springtime. The increase in ultraviolet radiation absorbed by the Sun seems to cause the lightening of the polar region. Credit: NASA, ESA, A. Simon (NASA-GSFC) and MH Wong (UC Berkeley); Image processing: A. Pagan (STScI)

Uranus

Hubble October 25and view of Uranus puts the planet’s bright northern polar cap in the spotlight. It is springtime in the northern hemisphere and the increase in ultraviolet radiation absorbed by the Sun appears to be causing the polar region to brighten. Researchers are studying how polar ice cap brightening results from changes in atmospheric methane concentration and haze particle characteristics, as well as atmospheric flow patterns. Curiously, even as the atmospheric hood becomes brighter, the sharp southernmost boundary remains fixed at the same latitude. This has been consistent over the past few years of OPAL observations, possibly because a jet stream sets up a barrier at this 43 degree latitude.

Hubble Neptune 2021

Hubble’s look at Neptune in 2021 revealed that a new storm, “dark spot”, discovered in 2018 has reversed direction and is moving north. Credit: NASA, ESA, A. Simon (NASA-GSFC) and MH Wong (UC Berkeley); Image processing: A. Pagan (STScI)

Neptune

In observations taken on September 7and, the researchers found that Neptune’s dark spot, which was recently found to have reversed its course from its equatorward move, is still visible in this image, along with a darkened northern hemisphere. There is also a noticeable dark, elongated circle encompassing Neptune’s south pole. The blue color of Neptune and Uranus is the result of the absorption of red light by the planets’ methane-rich atmosphere, combined with the same process of Rayleigh scattering that turns Earth’s skies blue. In 2021, there are few bright clouds on Neptune, and its distinct blue with a singular large dark patch is very reminiscent of what Voyager 2 saw in 1989.

Hubble Grand Tour 2021

From its vantage point above Earth’s atmosphere, NASA’s Hubble Space Telescope completed its grand tour of the outer solar system – Jupiter, Saturn, Uranus and Neptune – this year returning crisp images that complement current observations. and past interplanetary spacecraft. Credit: NASA, ESA, Amy Simon (NASA-GSFC), Michael H. Wong (UC Berkeley). Joseph DePasquale (STScI)

The Hubble Space Telescope is an international cooperation project between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland operates the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

Arline J. Mercier