solar system


Uranus is the seventh planet from the Sun and is the third largest in the solar system. It was discovered by William Herschel in 1781.

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Uranus is the seventh planet from the Sun, and the third-largest and fourth most massive planet in the Solar System. It is named after the ancient Greek deity of the sky Uranus (Ancient Greek) the father of Kronos (Saturn) and grandfather of Zeus (Jupiter).

Though it is visible to the naked eye like the five classical planets, it was never recognized as a planet by ancient observers because of its dimness and slow orbit. 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 was also the first planet discovered with a telescope.

Physical characteristics

Equatorial radius 25,559 ± 4 km
4.007 Earths[4][c]
Polar radius 24,973 ± 20 km
3.929 Earths[4][c]
Flattening 0.022 9 ± 0.000 8
Surface area 8.115 6 × 109 km²
15.91 Earths
Volume 6.833 × 1013 km³
63.086 Earths
Mass (8.6810 ± 0.0013) × 1025 kg
14.536 Earths
GM=5 793 939 ± 13 km³/s²
Mean density 1.27 g/cm³
Equatorial surface gravity 8.69 m/s²
0.886 g
Escape velocity 21.3 km/s
Sidereal rotation period -0.718 33 day
17 h 14 min 24 s[4]
Equatorial rotation velocity 2.59 km/s
9,320 km/h
Axial tilt 97.77°
North pole right ascension 17 h 9 min 15 s
North pole declination -15.175°
Albedo 0.300 (bond)
0.51 (geom.)
Surface temp. min mean max
1 bar level 76 K
0.1 bar 49 K 53 K 57 K
Apparent magnitude 5.9[7] to 5.32
Angular diameter 3.3"-4.1"

Uranus Interior


The plain aquamarine face of Uranus confirms the fact that Uranus is covered with clouds. The sameness of the planet's appearance shows that the planet's atmosphere is mostly composed of one thing, methane. The planet appears to be blue-green because the methane gas of the atmosphere traps red light and does not allow that color to escape. Beside clouds of methane crystals low in the atmosphere, smog, composed of ethane (the same product that can provide fuel for automobiles), is also present high in the atmosphere. The cloud particles constantly recycle themselves, first creating then destroying the heaviest crystals. This is an indication that Uranus' atmosphere is still evolving from its formation out of the solar nebula. Because Uranus lies on its side, Uranus has very strange seasons. Motions in the cloud patterns indicate that, like Jupiter and Saturn, the basic weather of Uranus can be described as a striped pattern of winds. This means that, even though the pattern is hard to see, Uranus is striped, just like Jupiter and Saturn.

Uranus Atmosphere

Scale height
27.7 km[2]
(Below 1.3 bar)
83 ± 3% Hydrogen (H2)
15 ± 3% Helium
2.3% Methane
0.009% Hydrogen
(0.007 - deuteride (HD)[12]
ammonium hydrosulfide (NH4SH)
methane (CH4)


Uranus Rings

uranus rings This pseudo-image of Uranus' rings was generated by using Voyager 2 frame FDS 26852.19. This image was taken in forward scattered light and shows dust bands not seen in any other image. A 3 pixel wide slice was taken from the most detailed part of the image, averaged to a 1 pixel wide image, then rotated 360 degrees and projected into perspective view. The real color of the rings are neutral gray and they are as dark as charcoal. (Courtesy A. Tayfun Oner)

Uranus and the Earth Compared

This image compares Uranus with Earth. Uranus is the fourth largest planet in the solar system, and is much larger than Earth, and mostly made of frozen gas.

Uranus' diameter is four times that of the Earth's

It has 15 times the mass of Earth's mass

If you weigh 180 pounds on Earth, you would weigh only 160 pounds at Uranus' cloud tops

Uranus is 19 times further from the Sun than the Earth


Uranus Orbital characteristics

Uranus orbit
Aphelion 3,004,419,704 km
20.083 305 26 AU
Perihelion 2,748,938,461 km 18.375 518 63 AU
Semi-major axis 2,876,679,082 km
19.229 411 95 AU
Eccentricity 0.044 405 586
Orbital period 30,799.095 days
84.323 326 yr
Synodic period 369.66 days[2]
Average orbital speed 6.81 km/s[2]
Mean anomaly 142.955 717°
Inclination 0.772 556° to Ecliptic
6.48° to Sun's equator
1.02° to Invariable plane[3]
Longitude of ascending node 73.989 821°
Argument of perihelion 96.541 318°
Satellites 27

Uranus Moons

"Sweet Moon," William Shakespeare wrote in A Midsummer Night's Dream, "I thank thee for thy sunny beams; I thank thee, Moon, for shining now so bright." Centuries later, the moons of Uranus pay homage to famous playwright.

While most of the satellites orbiting other planets take their names from Greek mythology, Uranus' moons are unique in being named for Shakespearean characters, along with a couple from the works of Alexander Pope.

Oberon and Titania (king and queen of the fairies) are the largest Uranian moons, and were first to be discovered - by William Herschel in 1787. William Lassell, who had been first to see a moon orbiting Neptune, discovered the next two, Ariel and Umbriel. Nearly a century passed before Gerard Kuiper found Miranda in 1948. And that was it until a NASA's robot made it to distant Uranus.

All of Uranus's inner moons (those observed by Voyager 2) appear to be roughly half water ice and half rock. The composition of the moons outside the orbit of Oberon remains unknown, but they are likely captured asteroids.

Miranda, the innermost and smallest of the five major satellites, has a surface unlike any other moon that's been seen. It has giant fault canyons as much as 12 times as deep as the Grand Canyon, terraced layers, surfaces that appear very old, and others that look much younger.

Ariel has the brightest and possibly the youngest surface among all the moons of Uranus. It has few large craters and many small ones, indicating that fairly recent low-impact collisions wiped out the large craters that would have been left by much earlier, bigger strikes. Intersecting valleys pitted with craters scars its surface.

Umbriel is ancient, and the darkest of the five large moons. It has many old, large craters and sports a mysterious bright ring on one side.

Oberon, outermost of the five major moons, is old, heavily cratered, and shows little signs of internal activity. Unidentified dark material appears on the floors of many craters.

Cordelia and Ophelia are shepherd moons that keep Uranus' thin, outermost "epsilon" ring well defined.

Between them and Miranda is a swarm of eight small satellites unlike any other system of planetary moons. This region is so crowded that astronomers don't yet understand how the little moons have managed to avoid crashing into each other. They may be shepherds for the planet's 10 narrow rings, and scientists think there must be still more moons, interior to any known, to confine the edges of the inner rings.



Titania [Ty-TAY-ne-ah] is the largest moon of Uranus. It is marked by a few large impact basins, but is generally covered with small craters and very rough rocks. The above image shows a 1,600 kilometer (1,000 mile) long trench. A large double walled crater can be seen towards the top of the image. There are many faults on Titania indicating there has been internal forces molding its surface.



Ariel [AIR-ee-al] is a relatively small satellite and is the brightest moon of Uranus. The surface is pock-marked with craters, but the most outstanding features are long rift valleys stretching across the entire surface. Canyons much like the ones on Mars appear in the pictures. The canyon floors appear as though they have been smoothed by a fluid. The fluid could not have been water because water acts like steel at these temperatures. The flow marks might have been made by ammonia, methane or even carbon monoxide.



Oberon [O-buh-ron] is a moon of Uranus that is characterized by an old, heavily cratered, and icy surface. The surface shows little evidence of internal activity other than some unknown dark material that apparently covers the floors of many craters. The above image shows several large impact craters towards the center of the image. On the limb, a high mountain rises 6 kilometers (4 miles) above its surroundings. There are bright rays similar to those seen on Jupiter's moon Callisto.

Uranus Moons

uranus moons

Uranus moons are shown in orbit in the image above


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