The planet Uranus in all its glory, between the rings and the moons, as pictured by James Webb


The planet Uranus recently photographed by the James Webb telescope with a system of rings and moons. Credit: NASA, ESA, CSA, STScI
Sergio Messina Sergio Messina 6 minutes

The planet Uranus it is penultimate, in order of distance from the Sun, among the planets of the Solar System (twenty times the Earth-Sun distance). It is classified as a frozen fig (4 times larger than Earth). It is more accurate mass of liquid ice (water ice, methane and ammonia) around a rocky core. Circulate completes a complete orbit around the Sun in about 81 yearsbut bike around each other with the period about 5 p.m.

The peculiarity of Uranus

However, there is a feature that makes it unique compared to other planets: Lits inclination of approximately 93 degrees relative to the normal to the orbital plane.

In fact, as the following figure shows, while Earth has an inclination of about 23 degrees and the other planets have similar inclinations, the planet Uranus literally lies on the orbital plane. This circumstance makes its rotation more like a “cylinder”.

The declination of the planet
The inclination of the axis of rotation of the planets with respect to the orbital plane. Uranus stands out among all the maximum inclination. Credit: Wikipedia

Due to this high inclination, the seasons on Uranus are extremely different from each other.

The existence of seasons, both on Earth and on other planets, is due to the fact that the axis of rotation is not perpendicular to the orbital plane, but inclined. The greater the slope, the greater the difference between the seasons.

In the case of Uranus, the inclination is maximal, so the difference between Uranian summer and Uranian winter is maximal compared to what happens on Earth (and all other planets).

Consider it summer on Uranus lasts about 20 years, and for 20 years the Sun remains continuously high in the sky without alternation of day and night. The same circumstance applies to winter That it also takes about 20 yearsduring which there is continuous night.

This situation leads to temperature differences and subsequent climate differences between summer and winter, much greater than what we experience on Earth.

But that is not the only peculiarity. In fact, unlike the other planets (with the exception of Venus), Uranus rotates clockwise on its axis, all others counter-clockwise.

It is believed that these two anomaliestilt and retrograde rotation, are the results of a massive impact of Uranus on another body in the Solar System during the early stages of its life.

What the recent JWST image shows

JWST photographed Uranus in the near-infrared band. And this also thanks to its high spatial resolution revealed an image that was not only highly suggestive but also rich in detail.

In the cover image the planet occupies a central position. It’s an ice giant planet whose pole appears covered by a cap (the brightest area of ​​the disk towards the right in the photo). Recall that since the planet “lies” on the orbital plane, its two poles are not up and down, but right and left.

In the lowest part of the shell we can glimpse some whitish fleeting structures that represent storms takes place in the planet’s atmosphere (which is made up of hydrogen, helium and methane).

The planet is then surrounded by concentric rings, among which very light and white stand out. This separates the so-called 9 inner rings gray colors from the remaining exteriors. We especially see that Between the inner rings and the planet is an elusive ring called the Z ring. Unlike Saturn’s rings, Uranus’ rings are much less reflective, so they are thought to consist mainly of small dust grains and rocks.

The same cover image with the names of some of the visible moons. NASA, ESA, CSA, STScI

Beyond the outer rings, some of the 27 moons identified so far orbiting the planet can be seen as bright white dots (marked in the image above).

Unlike the other planets’ moons, which are named after characters from Greek or Latin mythology (think of the moons Io, Europa, Ganymede, and Callisto of Jupiter), all of Uranus’ moons are named after characters from the works of William Shakespeare and Alexander. Pope.

Discovered by astronomer William Herschel in 1781, it has only been visited by one probe, Voyager 2. The surface characteristics are not at all consistent with the possibility of life forms.

Uranus and exoplanets

To date, around 2,000 exoplanets have been discovered that have properties similar to those of Uranus in terms of mass and size.. Exactly these exoplanets are coming classified as sub-Neptunians.

Additional study of Uranus and this type of planet opens a promising perspective for understanding their naturemeteorology, formation mechanisms, but also migration processes during the evolution of the planetary system.


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