Hubble has uncovered the secret of their colors

Carl Sagan and André Brahic unfortunately we are no longer able to comment on the discoveries made by giant planets in the Solar System but their colleagues continue to explore these worlds. If the gases Jupiter and Saturn we know better now after missions Juno and Cassini, the frozen – discovered by Herschel (Uranus) and Le Verrier (Neptune) – still holds a lot of mystery.

Only the investigation of Voyager 2 approached Uranus and Neptune, discovering the case of the latter a meteorology more active than expected for a planet so far away Sun (so received a small voice strength than Saturn), with such a place, black at this time, signifies a large storm planetary anti-cyclonic.

NASA’s Hubble Space Telescope has captured time-lapse images of a large dark storm on the missing Neptune. A new program called Hubble Atmosphere Legacy of the Outer Planets, or OPAL, provides annual global maps of our gas giant planets, allowing planetary scientists to see changes in formations such as Neptune’s dark storms. To get an accurate French translation, click on the white rectangle at the bottom right. English subtitles should be visible immediately. Then click the nut to the right of the rectangle, then “Subtitles” and finally “Automatic Translation”. Select “French”. © NASA Goddard Space Flight Center, Katrina Jackson

planetary scientists so have been content since the 1980s to continue their study of Uranus and Neptune using earth telescopes or with Hubble in orbit. We saw a new illustration of this with an article published on Journal of Geophysical Research: Planetsbut also free access to arXivshowing the work of an international group led by patrick irwinProfessor of physically planetary at Oxford University.

This work is based on the analysis of archival data covering several years first collected with Hubble, obtained with its spectro-imager (STIS) and fromultraviolet infrared, as well as the many images Hubble captured of Uranus and Neptune with myth Wide Field Camera 3 (WFC3). Data collected using a telescope Gemini Amihanan and theInfrared Telescope Facility (IRTF) sa in also proved valuable.

These observations feed the scholars model of radiative transfer to atmospheres of the two giants (and these atmospheres themselves) which are mostly composed of ice and which now allow astronomers better understand why others mass and very similar rays, and very similar compositions and structures, Uranus and Neptune have different colors.

Layers of aerosol haze and various atmospheric turbulence

Initially, planetary scientists were just looking for a model that would help understand clouds and the fog in the atmosphere of ice giants. But, as Mike Wong, an astronomer at the University of California at Berkeley and member of the team behind the discovery of the colors of Uranus and Neptune, determined in a press release, ” Explaining the color difference between Uranus and Neptune is an unexpected bonus! “.

Irwin explains that “ this is the first model of simultaneous attention to the observations of LIGHT appeared in the solar wavelengths ultraviolet to near infrared. It is also the first to explain the visible color difference between Uranus and Neptune. “.

As explained in more detail in the diagrams below, the researchers ’new model includes three layers of aerosol haze (note that one aerosol a suspension of fine droplets or particles in a gasfor example in the form of smoke or fog) at different atmospheric heights on each planet. the middle layer haze particles, above the level of condensation methane, became thicker on Uranus than Neptune and this is what affects the visible color of the two planets.

As in the case of explaining the blue color of the sky and the white color of the Earth’s clouds, planetary scientists are considering their models to Rayleigh and Mie light scattering effectsnamed after physicists involved in explaining these effects more than a century ago.

Jet streams affect only Neptune and Uranus above

Article on Laurent Sacco published on 05/23/2013

the jet streams of Neptune and Uranus because they are just above, according to a group of planetary scientists. This is the conclusion reached by the researchers, who have not directly studied the gravitational field produced by the two. gas giants. The method they use should be applicable to Jupiter in a few years.

The conquest of space allowed the birth of a comparative planetology, in which the tools of internal and external geophysics, tested on Earth, were used to test the understanding of geology and the climatology from other planets Solar system. In this way it is possible to learn more about our planet itself.

You cannot change soil mass, its composition or its temperature as the laboratory would do to better understand a physical system. But ‘universe is responsible for conducting these experiments with a variety of star in the solar system. Thus we can transfer the models to climate on the ground of March and Venusto determine whether they could predict, through simulations, the meteorology of the planets.

Like the researchers Yohai Kaspifrom Department of Environmental Sciences from Weizmann Institute of Science (Israel), is also trying to understand the climate of gas giants like Jupiter and Saturn. The geophysicist recently co-published, on NATUREan article in which he gives a recent evaluation of the thickness of the layers where jet streams (Diin jet streamsin English) in Neptune and Uranus.

Wind gusts of 1,000 km/h on Neptune and Uranus

From mission observations Traveler 2we know it is WIND violent ones are on the surface of the two planets, and that they are still blowing there in a rapidly more than 1,000 km/h. Types of storms whose size is greater than the Earth will also occur there.

It was also a surprise for astrophysicistsnot expecting to see so much activity on frozen planets with low energy from the light of Sun, since they are located at a distance of a few billion kilometers from it. Although the the planet uranus has a strong tilt axis of rotation, so that it is almost parallel to the orbital plane of the planet, and that one of its poles is almost opposite the Sun. winterwe see that the atmospheric phenomena of Uranus and Neptune very similar.

To find out what happened to atmospheres of these giants, it is necessary to specify the models in their internal structure. We can use the laws of physics to construct it, but we need to control them through observations and measurements. For example, it is possible to use magnetic field where the field of gravity planets for this purpose. As such the measurements by gravimetry on the mission Grill gives us information about the contents of month.

A method of exploring Jupiter and exoplanets

However, it turns out that the gravitational field affects the flow characteristics of fluids on a rotating planet. On Earth, this is a fact known to external geophysicists. So the velocity field The air shows that they wrap the areas with low and high pressure. By estimating these pressures, we can return to the unequal gravitational field of the planet and ultimately to the distribution properties of things in the inner layers. This is exactly what the researchers realized, based on data about the jet streams of Neptune and Uranus.

Planetologists conclude that jet streams should not reach depths of more than 1,000 km. Note that the radii of Neptune and Uranus are approximately 24,600 and 25,400 km respectively.

When the missions Juno and Juice coming close to Jupiter, the data they collect should make it possible to use the same method by researchers, in order to prevent the internal structure of the largest planet in the Solar System. We should, in the future, be able to do the same hot Jupiters.

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