Uranus

Photograph of Uranus in true colour (by Voyager 2 in 1986)
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Simulated Earth view of Uranus from 1986 to 2030, from southern summer solstice in 1986 to equinox in 2007 and northern summer solstice in 2028.
Size comparison of Earth and Uranus
Diagram of the interior of Uranus
Uranus's atmosphere taken during the Outer Planet Atmosphere Legacy (OPAL) program.
Aurorae on Uranus taken by the Space Telescope Imaging Spectrograph (STIS) installed on Hubble.
The magnetic field of Uranus
(animated; 25 March 2020)
The first dark spot observed on Uranus. Image obtained by the HST ACS in 2006.
Uranus in 2005. Rings, southern collar and a bright cloud in the northern hemisphere are visible (HST ACS image).
Major moons of Uranus in order of increasing distance (left to right), at their proper relative sizes and albedos (collage of Voyager 2 photographs)
Uranus's aurorae against its equatorial rings, imaged by the Hubble telescope. Unlike the aurorae of Earth and Jupiter, those of Uranus are not in line with its poles, due to its lopsided magnetic field.
Crescent Uranus as imaged by Voyager 2 while en route to Neptune

Seventh planet from the Sun.

- Uranus
Photograph of Uranus in true colour (by Voyager 2 in 1986)

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Artist's impression of the formation of a gas giant around the star HD 100546

Gas giant

Giant planet composed mainly of hydrogen and helium.

Giant planet composed mainly of hydrogen and helium.

Artist's impression of the formation of a gas giant around the star HD 100546

The term “gas giant” was originally synonymous with “giant planet”, but in the 1990s it became known that Uranus and Neptune are really a distinct class of giant planets, being composed mainly of heavier volatile substances (which are referred to as “ices”).

The Solar System's four giant planets against the Sun, to scale

Giant planet

The giant planets constitute a diverse type of planet much larger than Earth.

The giant planets constitute a diverse type of planet much larger than Earth.

The Solar System's four giant planets against the Sun, to scale
Relative masses of the giant planets of the outer Solar System
These cut-aways illustrate interior models of the giant planets. Jupiter is shown with a rocky core overlaid by a deep layer of metallic hydrogen.
Saturn's north polar vortex
An artist's conception of 79 Ceti b, the first extrasolar giant planet found with a minimum mass less than Saturn.
Comparison of sizes of planets of a given mass with different compositions

There are four known giant planets in the Solar System: Jupiter, Saturn, Uranus and Neptune.

1785 portrait by Lemuel Francis Abbott

William Herschel

German-born British astronomer and composer.

German-born British astronomer and composer.

1785 portrait by Lemuel Francis Abbott
Original manuscript of Symphony No. 15 in E-flat major (1762)
Replica in the William Herschel Museum, Bath, of a telescope similar to that with which Herschel discovered Uranus
Herschel's mirror polisher, on display in the Science Museum, London
Uranus, discovered by Herschel in 1781
NGC 2683 is an unbarred spiral galaxy discovered by William Herschel on 5 February 1788
William and Caroline Herschel polishing a telescope lens (probably a mirror); 1896 lithograph
The 40-foot (12 m) telescope
A Cassini orbiter's view of Mimas, a moon of Saturn discovered by Herschel in 1789.
William Herschel's model of the Milky Way, 1785
William Herschel's coat of arms deemed a notorious example of debased heraldry: Argent, on a mount vert a representation of the 40 ft. reflecting telescope with its apparatus proper on a chief azure the astronomical symbol of Uranus irradiated or. Crest: A demi terrestrial sphere proper thereon an eagle, wings elevated or
William Herschel, portrait by James Sharples, c. 1805

This would, after several weeks of verification and consultation with other astronomers, be confirmed to be a new planet, eventually given the name of Uranus.

Voyager 2

Space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere.

Space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere.

see diagram
Animation of Voyager 2s trajectory around Jupiter ·····
The trajectory of Voyager 2 through the Jovian system
Voyager 2 left the heliosphere on November 5, 2018.
Voyager 1 and 2 speed and distance from Sun
On Voyager 2, both PWS and PRS have remained active, whereas on Voyager 1 the PRS has been off since 2007
NASA map showing trajectories of the Pioneer 10, Pioneer 11, Voyager 1, and Voyager 2 spacecraft.
The current position of Voyager 2 as of December 2018. Note the vast distances condensed into an exponential scale: Earth is one astronomical unit (AU) from the Sun; Saturn is at 10 AU, and the heliopause is at around 120 AU. Neptune is 30.1 AU from the Sun; thus the edge of interstellar space is around four times as far from the Sun as the last planet.
Voyager Golden Record
RTG inner heat source
RTG assembly
RTG unit
Voyager 2 launch on August 20, 1977, with a Titan IIIE/Centaur.
thumb|Animation of Voyager 2{{'s}} trajectory from August 20, 1977, to December 30, 2000
Trajectory of Voyager 2 primary mission.
Plot of Voyager 2{{'s}} heliocentric velocity against its distance from the Sun, illustrating the use of gravity assists to accelerate the spacecraft by Jupiter, Saturn and Uranus. To observe Triton, Voyager 2 passed over Neptune's north pole, resulting in an acceleration out of the plane of the ecliptic, and, as a result, a reduced velocity relative to the Sun.<ref>{{cite web |url=https://solarsystem.nasa.gov/basics/bsf4-1.php |title=Basics of space flight: Interplanetary Trajectories}}</ref>

A part of the Voyager program, it was launched 16 days before its twin, Voyager 1, on a trajectory that took longer to reach gas giants Jupiter and Saturn but enabled further encounters with ice giants Uranus and Neptune.

The chemical elements ordered in the periodic table

Volatiles

Volatiles are the group of chemical elements and chemical compounds that can be readily vaporized.

Volatiles are the group of chemical elements and chemical compounds that can be readily vaporized.

The chemical elements ordered in the periodic table

Thus, Jupiter and Saturn are gas giants, and Uranus and Neptune are ice giants, even though the vast majority of the "gas" and "ice" in their interiors is a hot, highly dense fluid that gets denser as the center of the planet is approached.

John Flamsteed by Thomas Gibson, 1712

John Flamsteed

English astronomer and the first Astronomer Royal.

English astronomer and the first Astronomer Royal.

John Flamsteed by Thomas Gibson, 1712
Plaque marking the grave of John Flamsteed and his wife in the chancel of St Bartholomew's Church in Burstow, Surrey
Bust of John Flamsteed in the Museum of the Royal Greenwich Observatory

He also made the first recorded observations of Uranus, although he mistakenly catalogued it as a star, and he laid the foundation stone for the Royal Greenwich Observatory.

Methane bubbles can be burned on a wet hand without injury.

Methane

Chemical compound with the chemical formula .

Chemical compound with the chemical formula .

Methane bubbles can be burned on a wet hand without injury.
Testing Australian sheep for exhaled methane production (2001), CSIRO
This image represents a ruminant, specifically a sheep, producing methane in the four stages of hydrolysis, acidogenesis, acetogenesis, and methanogenesis.
This diagram shows a method for producing methane sustainably. See: electrolysis, Sabatier reaction
Methane (CH4) measured by the Advanced Global Atmospheric Gases Experiment (AGAGE) in the lower atmosphere (troposphere) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in parts-per-billion.
Methane (CH4) on Mars – potential sources and sinks
Alessandro Volta

This is what gives Uranus and Neptune their blue or bluish-green colors, as light passes through their atmospheres containing methane and is then scattered back out.

Pictured in natural color approaching equinox, photographed by Cassini in July 2008; the dot in the bottom left corner is Titan

Saturn

Sixth planet from the Sun and the second-largest in the Solar System, after Jupiter.

Sixth planet from the Sun and the second-largest in the Solar System, after Jupiter.

Pictured in natural color approaching equinox, photographed by Cassini in July 2008; the dot in the bottom left corner is Titan
The symbol for Saturn in late Classical (4th & 5th c.) and medieval Byzantine (11th c.) manuscripts, derives from (kappa-rho).
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Composite image comparing the sizes of Saturn and Earth
Diagram of Saturn, to scale
Methane bands circle Saturn. The moon Dione hangs below the rings to the right.
A global storm girdles the planet in 2011. The storm passes around the planet, such that the storm's head (bright area) passes its tail.
Saturn and rings as viewed by the Cassini spacecraft (28 October 2016)
A montage of Saturn and its principal moons (Dione, Tethys, Mimas, Enceladus, Rhea and Titan; Iapetus not shown). This image was created from photographs taken in November 1980 by the Voyager 1 spacecraft.
Possible beginning of a new moon (white dot) of Saturn (image taken by Cassini on 15 April 2013)
Galileo Galilei observed the rings of Saturn in 1610, but was unable to determine what they were
Robert Hooke noted the shadows (a and b) cast by both the globe and the rings on each other in this drawing of Saturn in 1666.
Pioneer 11 image of Saturn
At Enceladus's south pole geysers spray water from many locations along the tiger stripes.
Amateur telescopic view of Saturn
Simulated appearance of Saturn as seen from Earth (at opposition) during an orbit of Saturn, 2001–2029
Saturn eclipses the Sun, as seen from Cassini. The rings are visible, including the F Ring.
orientation of its rings
HST Saturn portrait from 20 June 2019
Farewell to Saturn and moons (Enceladus, Epimetheus, Janus, Mimas, Pandora and Prometheus), by Cassini (21 November 2017).

Its equatorial and polar radii differ by almost 10%: 60,268 km versus 54,364 km. Jupiter, Uranus, and Neptune, the other giant planets in the Solar System, are also oblate but to a lesser extent.

The planet Mars has an atmosphere composed of thin layers of gases.

Atmosphere

Layer of gas or layers of gases that envelope a planet, and is held in place by the gravity of the planetary body.

Layer of gas or layers of gases that envelope a planet, and is held in place by the gravity of the planetary body.

The planet Mars has an atmosphere composed of thin layers of gases.
The atmospheric gases around Earth scatter blue light (shorter wavelengths) more than light toward the red end (longer wavelengths) of the visible spectrum; thus, a blue glow over the horizon is seen when observing Earth from outer space.
A diagram of the layers of Earth's atmosphere
Graphs of escape velocity against surface temperature of some Solar System objects showing which gases are retained. The objects are drawn to scale, and their data points are at the black dots in the middle.

The low temperatures and higher gravity of the Solar System's giant planets—Jupiter, Saturn, Uranus and Neptune—allow them more readily to retain gases with low molecular masses.

Ball-and-stick model of the diamminesilver(I) cation, [Ag(NH3)2]+

Ammonia

Compound of nitrogen and hydrogen with the formula NH3.

Compound of nitrogen and hydrogen with the formula NH3.

Ball-and-stick model of the diamminesilver(I) cation, [Ag(NH3)2]+
Ball-and-stick model of the tetraamminediaquacopper(II) cation, [Cu(NH3)4(H2O)2](2+)
Jabir ibn Hayyan
This high-pressure reactor was built in 1921 by BASF in Ludwigshafen and was re-erected on the premises of the University of Karlsruhe in Germany.
A train carrying Anhydrous Ammonia.
Liquid ammonia bottle
Household ammonia
Ammoniacal Gas Engine Streetcar in New Orleans drawn by Alfred Waud in 1871.
The X-15 aircraft used ammonia as one component fuel of its rocket engine
Anti-meth sign on tank of anhydrous ammonia, Otley, Iowa. Anhydrous ammonia is a common farm fertilizer that is also a critical ingredient in making methamphetamine. In 2005, Iowa used grant money to give out thousands of locks to prevent criminals from getting into the tanks.
The world's longest ammonia pipeline (roughly 2400 km long), running from the TogliattiAzot plant in Russia to Odessa in Ukraine
Hydrochloric acid sample releasing HCl fumes, which are reacting with ammonia fumes to produce a white smoke of ammonium chloride.
Production trend of ammonia between 1947 and 2007
Main symptoms of hyperammonemia (ammonia reaching toxic concentrations).
Ammonia occurs in the atmospheres of the outer giant planets such as Jupiter (0.026% ammonia), Saturn (0.012% ammonia), and in the atmospheres and ices of Uranus and Neptune.

Ammonia is also found throughout the Solar System on Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto, among other places: on smaller, icy bodies such as Pluto, ammonia can act as a geologically important antifreeze, as a mixture of water and ammonia can have a melting point as low as 173 K if the ammonia concentration is high enough and thus allow such bodies to retain internal oceans and active geology at a far lower temperature than would be possible with water alone.