Courtesy of the Israeli Astronomical Society
Moran Nachshoni
Direct link to this page: https://www.hayadan.org.il/jupiterprofile1.html
Jupiter and Saturn are the largest planets in the solar system, more than 10 times the diameter of Earth. They belong to the gas giant family. In the coming months they will grace the evening sky with their glow. It's just the time to learn a little more about the giant planets before pointing the telescopes at them for a delightful observation.
Jupiter
Being the fourth brightest object in the sky (after the Sun, Moon and Venus), Jupiter has always intrigued scientists. The discovery of its system of moons, Io, Europa Ganymede and Callisto, in 1610 by Galileo Galilei, was the first discovery of a motion system whose center is not on Earth. It was one of the pillars of Copernicus' heliocentric theory, and Galileo's support of it caused him serious problems with the Inquisition.
Jupiter is a gas giant, meaning it is made entirely of gases that are compressed as you go deeper into it, and it has no solid ground to land on. The figure seen in telescopes consists of clouds at a height of a little above a pressure of one atmosphere. It is composed of 90% hydrogen and 10% helium, with very little methane, water, ammonia and silicates, a composition very similar to that of the early solar system.
a building
Jupiter probably has a rocky core with a mass 10-15 times the mass of the Earth. Above the nucleus is the liquid-metallic hydrogen layer. This material basically consists of protons and free electrons, similar to the core of the sun, but at much lower temperatures. This happens thanks to a tremendous pressure of 4 million atmospheres. At Jupiter's temperatures and pressures, hydrogen is a liquid and not a gas, an electrical conductor, and is the cause of Jupiter's massive magnetic field. The outer layer contains molecular hydrogen and helium, in addition to other substances present in very small amounts.
Jupiter is believed to have three layers of clouds - ammonia ice,
Ammonia hydrosulphide, and a mixture of ice and water. In 1995, the Galileo spacecraft arrived at Jupiter and with it a probe that penetrated as deep as possible into Jupiter to discover its hidden secrets. Two devices that were on top of the probe showed very faint traces to the two upper layers, but apparently the penetration area was unusual - warm and relatively cloudless.
Information from the probe also showed that there is not exactly as much water as the theories predicted. The expectations were for an amount of oxygen twice as high as the sun (together with hydrogen it forms water). Other surprising findings are the high temperature and density in the upper atmosphere.
clouds
In Jupiter and the other gas giants, winds blow at very high speeds throughout the entire length of the sphere. Small changes in chemistry and temperature between the belts cause differences in color between them. While the existence of the belts has been known for many years, the eddies in the regions between the belts were only discovered when spacecraft arrived at Jupiter. The information from Galileo's probe showed that the wind speed there is higher than expected - over 600 km/h, and continues to the depth where the probe continued to transmit data and maybe even more. It was found that the atmosphere of Jupiter is very turbulent, which indicates that the atmospheric processes are driven by the internal heat of Jupiter more than the solar radiation.
The colors of the clouds are probably caused by chemical reactions of the element sulfur, but this is only a hypothesis at the moment. The colors of the clouds indicate their height - the blue ones are the lowest, followed by the brown and white ones, while the red ones are the highest.
storms
The red eye of Jupiter has been observed for more than 300 years. Its discovery is attributed to Cassini or Robert Hooke in the 17th century. Its shape is oval, and its dimensions are 12,000 by 25,000 km (!), enough to contain two Earth globes. From infrared observations it becomes clear that the red eye is a high pressure area whose cloud tops are significantly higher than the environment. Similar structures have been observed on Saturn and Neptune, but it is still unclear how these huge structures exist for such a long time.
energy balance
Jupiter emits more energy into space than it receives from the Sun. Jupiter's core is very hot - probably 20,000 degrees Kelvin. Unlike the sun, where the heat is produced by thermonuclear reactions of nuclear fusion of atoms, the heat is produced by the Kelvin-Helmholtz effect - a slow gravitational compression of the planet. The internal heat probably causes extensive convection zones in the layers above the core, resulting in complex flows of clouds in the upper atmosphere. This is also observed in Saturn and Neptune, but strangely, not in Uranus. The size of Jupiter is almost the largest a gas giant can be - adding more material would only compress it further, with a tiny increase in its total volume.
magnetic field
Jupiter has a huge magnetic field - it reaches a great distance, up to 650 million (!) km on the opposite side of the Sun, beyond the orbit of Saturn. Jupiter's moons reside within this field, which may explain the volcanic activity of Io, the closest moon to Aloy. These radiation zones are similar, but much stronger than the "Van Allen belts" discovered on Earth. The probe even discovered a third radiation belt, 10 times stronger than the Van Allen belts above the upper atmosphere.
Rings
Jupiter has a ring system similar to Saturn, but much paler and smaller. No one expected to find rings around Jupiter, and only after the insistence of 2 scientists was it finally discovered by the Voyager 1 spacecraft. Jupiter's rings are extremely dark - reflecting only 0.05% of the light that falls on them, and are probably made of grains of rocky material, unlike Saturn's rings which are made of ice . Jupiter's rings are dynamic - the particles do not stay there for a relatively long time. The Galileo spacecraft discovered evidence that the rings receive a fresh supply of dust, created by the impact of micro-meteors, accelerated by the strong electric field, in the inner moons.
moons
Jupiter has 39 moons, of which the four largest ones were discovered by Galileo Galilei, and another 12 small moons with mythological names, and the other 23 small moons that were recently discovered do not yet have names.
Jupiter slows its rotation at a very slow rate due to tidal forces caused by the four Galilean moons. These forces also cause these moons to gradually move away from him. Io, Europa, and Ganymede are trapped in a 1:2:4 resonant orbit (ie, Io rotates twice as fast as Europa and four times as fast as Ganymede). Callisto is in a near-resonant orbit, and in a few million years it will also be caught in such a resonant orbit, and will circle in an orbit twice that of Ganymede.
In recent years, the evidence for the existence of an ocean of liquid water under the surface of Europa is increasing. Many signs testify to this - fractures in the ice layer that surrounds the moon, young surfaces free of ancient craters indicate an active nature, and the presence of a magnetic field indicating a molten and hot core. It is easy to imagine that in a layer of water where the temperature ranges from 0-100 degrees, it is possible for life to exist at a primitive and perhaps even complex level. Branched food systems have already been observed in the ocean bottoms on Earth in places where sunlight does not reach. At the bottom of these systems, bacteria were found that feed on sulfur emitted from the flares of underwater volcanoes, which do not need air or light. It is likely that a similar system may exist in Europe as well. Future space missions that will be launched towards the frozen moon will try to find out, using a special radar, the thickness of the outer layer of ice, thus paving the way for a spacecraft that will land and penetrate the ice, on its way to discovering the mystery hidden in it.
Shoemaker Levy 9
In July 1994, the comet Shoemaker Levy 9 hit Jupiter. After it was discovered broken into more than 20 fragments, it became clear that its trajectory was leading it straight into Jupiter. Unfortunately for us, the impact was on the side that was hidden from us at the time of the impact, but the impact area appeared about 20 minutes later due to the rapid rotation of Jupiter around its axis. Each fragment of a comet left its mark on Jupiter in the form of a dark spot in the atmosphere, and the many spots could be seen even in amateur telescopes. The result of these impacts was also observed a year after the impact by the Hubble Space Telescope.
The website of the Israeli Astronomical Society
Yedan was right
The Guide to the Cosmos - Dvir Lexicon of Astronomy and Astrophysics - John Gribbin on the Mythos website
https://www.hayadan.org.il/BuildaGate4/general2/data_card.php?Cat=~~~524979435~~~19&SiteName=hayadan
