Uranus

Uranus . It is the seventh planet in the Solar System , the third in size, and the fourth most massive. It is named after the Greek god of the skies Uranus, father of Cronus ( Saturn ). Although it is detectable with the naked eye in the night sky, it was not classified as a planet by ancient astronomers due to its low luminosity. Sir William Herschel announced its discovery on March 13 , 1781 , expanding the known boundaries of the Solar System for the first time in modern history. Uranus is also the first planet discovered through a telescope .

The main characteristic of Uranus is the inclination of its axis of rotation of almost ninety degrees with respect to its orbit ; The tilt is not limited only to the planet itself, but also to its rings, satellites and magnetic field. Uranus also has the most uniform surface of all the planets in the Solar System, with its characteristic blue-green color, produced by the combination of gases present in its atmosphere, and it has a ring system that cannot be observed with the naked eye. It also has a blue ring, a true planetary rarity. Uranus is one of two planets in the Solar System that has a retrograde motion , the other being Venus .

Summary

[ disguise ]

• 1 Discovery
• 2 Physical characteristics
• 3 Rings
• 4 Moons
• 5 Views
  • 1 Ring details
• 6 Related articles
• 7 References
• 8 Sources

Discovery

Uranus was the first planet discovered that was not known in ancient times, although it had been observed and confused with a star on many occasions. The oldest known record of it is due to John Flamsteed , who cataloged it as star 34 Tauri in 1691 . The French astronomer Pierre Le Monnier also observed it at least twelve times between 1750 and 1769 .

Sir William Herschel , a German musician and astronomer at the court of King George III of England , discovered the planet on March 13 , 1781 , using a telescope he built himself, although he initially reported that it was a comet . He gave the name Georgium Sidus (George’s Star) in honor of the king who had just lost the British colonies in America , but had gained a star. However, the name did not survive beyond Great Britain .

Lalande , a French astronomer, proposed calling it Herschel after its discoverer; The Swedish astronomer Erik Prosperin , for his part, proposed the name Neptune for the new discovered planet, something that many of his colleagues seconded. Finally, it was the German astronomer Johann Elert Bode who coined the name Uranus, father of Cronus (whose Roman equivalent gave his name to Saturn ), arguing that since Saturn was the father of Jupiter, it was most logical that the new planet would take its name after turn of the father of Saturn.

It is, in fact, the only planet whose name is derived from a figure in Greek mythology (its Roman counterpart is Caelus ). By 1827 , Uranus was the most commonly used name for the planet even in Britain. The HM Nautical Almanac, however, continued to list it as Georgium Sidus until 1850 .

The astronomical symbol of Uranus is represented as. It is a hybrid between the symbols of the planet Mars and the Sun , since Uranus was god and personification of the sky in Greek mythology, which they believed dominated by the combined powers of the Sun and Mars. The astrological symbol, however, is suggested by Lalande in 1784 . In a letter to Herschel, Lalande described it as “un globe surmonté par la première lettre de votre nom” (“a globe crowned by the first letter of his surname”). In the languages ​​of China , Vietnam , Japan and Korea the literal translation of the planet’s name is the queen star of the sky (天王星) in Japanese and Chinese.

Physical characteristics

Orbit and axial inclination of the axis of rotation. The orbit of Uranus is 84 Earth years. Its average distance from the Sun is approximately 3,000 million kilometers (about 20 AU). The characteristics of Uranus’s orbit were initially calculated by Pierre Simón Laplace in 1783 . It did not take long for the discrepancies between forecasts and observations to become evident, until in 1841 John Couch Adams suggested that these differences were perhaps due to the gravitational influence of a planet not yet discovered. In 1845 , Urbain Le Terrier began an independent study of the orbit of Uranus. On September 23, 1846, Johann Gottfried Galle located the new planet, which would later be named Neptune , very close to the position calculated for it by Le Verrier.

The rotational period of the interior of Uranus is 17 hours and 14 minutes, however, as on the other giant planets, the upper atmosphere experiences strong winds in the direction of its rotation, so at some latitudes, large areas of This atmosphere can rotate in just 14 hours. The rotation of Uranus, like that of Venus, is retrograde and its axis is inclined almost 90º degrees to the plane of its orbit. During half of each orbit, that is, for 42 years, the north pole points directly towards the Sun, and during the other half of the orbit it is the southern hemisphere that receives sunlight, while the northern hemisphere remains in a long freezing night. Only a relatively narrow strip around the equator experiences a normal pattern of days and nights.

The reasons why the planet’s axis is tilted to such a high degree are not known, although it is speculated that perhaps during its formation the planet may have collided with a large protoplanet capable of producing this anomalous orientation. Another possibility is that gravitational disturbances exerted by the Solar System’s other giant planets forced it to tilt this way. One of the results of the axial tilt of Uranus is that its polar regions receive more solar energy during the course of the year than the equatorial regions, however, the temperature of Uranus is higher at its equator than at its poles. The mechanism that causes this circumstance is still unknown.

Rings

Uranus Rings

In 1977 , the first nine rings of Uranus were discovered. During the Voyager visits, these rings were photographed and measured, as were the other new rings. The rings of Uranus are clearly different from those of Jupiter and Saturn. The outermost of the rings, epsilon, is composed of ice rocks several feet across. There also appears to be a faint distribution of dust throughout the ring system. There could also be a large number of narrow, or possibly incomplete, rings or ring arcs, with widths not reaching 50 meters (160 feet). The individual particles in the rings have low reflectivity. At least one of the rings, the epsilon, has a gray color. The moons Cordelia and Ofelia act as companion satellites of the epsilon ring.

In January 1986 , four more rings were discovered during Voyager 2’s exploratory voyage. During the visits of the Voyager spacecraft, these rings were photographed and measured. The rings of Uranus are clearly different from those of Jupiter and Saturn . The outermost of the rings, epsilon, is composed of ice rocks several meters across. There also appears to be a faint distribution of dust throughout the ring system. There could also be a large number of narrow, or possibly incomplete, rings or ring arcs, with widths not reaching 50 metres. The individual particles in the rings have a low reflectivity. At least one of the rings, the epsilon, has a gray color. The moons Cordelia and Ofelia act as companion satellites of the epsilon ring.

All 9 known rings of Uranus can be seen here. The fine lines seen between the rings are the result of image processing. Six small-angle images have been used to extract color information from the extremely dark and faint rings. The final image has been created from three color offsets and represents a false color view. The image shows that the brightest ring, epsilon, at the top has a neutral color, with the other 8 remaining showing color differences between them.

Moons

Uranus has 15 satellites (5 discovered through the telescope and 10, by Voyager 2); They all revolve around their equator and move in the same direction in which the planet rotates. The two largest moons, Oberon and Titania, were discovered by Herschel in 1787. The next two, Umbriel and Ariel, were discovered by the British astronomer William Lassell in 1851 . Miranda, the innermost satellite known before Voyager, was discovered in 1948 by American astronomer Gerard Pieter Kuiper.

A team of scientists, working with the Hale telescope at Mount Palomar Observatory, announced the discovery of two new moons of Uranus in November 1997 . Until the International Astronomical Union certifies the discovery, the satellites will not receive the final name. These are the two most distant moons of the planet, with relatively small diameters.

Views

These two images of Uranus, one in true color (left) and the other in false color

These two images of Uranus, one in true color (left) and the other in false color, were created from images sent on January 17 , 1986 by Voyager 2’s small-angle camera. The spacecraft was 9.1 million kilometers (5.7 million miles) from the planet, several days before the point of closest approach. The image on the left has been processed to show Uranus as the human eye would see it from the ship’s vantage point. The image is a composite of several shots taken with the blue, green and orange filters.

The darker shadows at the top right of the disk correspond to the planet’s day and night boundary. Beyond this zone is the hidden northern hemisphere of Uranus, which remains in total darkness as the planet rotates. The blue-green color is the result of the absorption of blue light by the menthane that makes up the deep, cold and extraordinarily clear atmosphere of Uranus.

The view on the right uses false colors and greatly increased contrast to highlight fine details in Uranus’s polar region. The images obtained through the ultraviolet, violet and orange filters were respectively converted to the same blue, green and red colors that were used to generate the view on the left. The little contrast visible in true color is greatly exaggerated here.

Details of the rings

Image captured by the James Webb Space Telescope .

In April 2023 , NASA released an image ^[1] of Uranus taken by the James Webb Space Telescope where 11 of the 13 rings that form it can be seen. Some of the rings look so shiny that they appear to be a single larger ring.

When the Voyager 2 spacecraft flew by Uranus in 1986 , its camera showed an almost featureless blue-green ball.

But the infrared wavelengths and sensitivity of the Webb instead reveal spectacular rings.

The image also revealed some of the 27 known moons of Uranus, although most are too small to be seen in the image.