- Mass: 8.68 x 10^25 kg
- Diameter: 51118 km
- Mean density: 1290 kg/m^3
- Escape velocity: 21300 m/sec
- Average distance from Sun: 19.18 AU
- Rotation period: 17.9 hours
- Revolution period: 84 years
- Obliquity: 97.9°
- Orbit inclination: 0.77°
- Orbit eccentricity: 0.047°
- Mean temperature: 59° K
- Visual geometric albedo: 0.56
- Atmospheric components: 83% hydrogen, 15% helium, 2% methane (at depth)
- Rings: Uranus has a system of narrow, faint rings. Ring particles are dark, and could consist of rocky or carbonaceous material.
This image reveals many broad lanes of dust surrounding the 9 main rings of Uranus. It was taken by Voyager 2 looking back toward the sun through the ring system. The dust is especially bright in this view, for the same reason that we can see dust on a windshield better when we are driving toward the sun. The rings of Uranus are actually very dark; their albedo is only a few percent. The short stubby streaks are stars slightly smeared during the long exposure.
The Uranian rings were the first after Saturn's to be discovered. This was of considerable importance since we now know that rings are a common feature of planets, not a peculiarity of Saturn alone.
The 9 main rings of Uranus are visible here as horizontal lines. The somewhat
fainter, pastel lines seen between the rings are artifacts of computer
enhancement. Six narrow-angle images were used to extract color information
from the extremely dark and faint rings. The final image was made from three
color averages and represents an enhanced, false-color view. The image shows
that the brightest, or epsilon ring at top is neutral in color, with the
fainter 8 remaining rings showing slight color differences between them.
Uranus has 20 named moons plus 1 recently discovered one which as yet has not been given an official name. Uranus has the most known moons of any of the planets. Unlike the other bodies in the solar system which have names from classical mythology, Uranus' moons take their names from the writings of Shakespeare and Pope. The five major moons of Uranus are: Miranda, Ariel, Umbriel, Titania, and Oberon.
They form three distinct classes: the 11 small very dark inner ones discovered by Voyager 2, the 5 large ones, and the newly discovered much more distant ones. Most have nearly circular orbits in the plane of Uranus' equator at a large angle to the plane of the ecliptic; the outer 4 are much more elliptical.
Voyager 2 discovered 10 small moons in addition to the 5 large ones already known. It is likely that there are several more tiny satellites within the rings.
Uranus is the seventh planet from the Sun and the third largest by diameter. Uranus is larger in diameter but smaller in mass than Neptune. Uranus is the ancient Greek deity of the Heavens, the earliest supreme god.
Uranus, the first planet discovered in modern times, was discovered by William Herschel while systematically searching the sky with his telescope on March 13, 1781. It had actually been seen many times before but ignored as simply another star the earliest recorded sighting was in 1690 when John Flamsteed cataloged it as 34 Tauri. Herschel named it "the Georgium Sidus" or the Georgian Planet in honor of his patron, King George III of England; others called it "Herschel". The name Uranus was first proposed by Bode in conformity with the other planetary names from classical mythology but didn't come into common use until 1850.
Uranus' magnetic field is odd in that it is not centered on the center of the planet and is tilted almost 60 degrees with respect to the axis of rotation. It is probably generated by motion at relatively shallow depths within Uranus. Most of the planets spin on an axis nearly perpendicular to the plane of the ecliptic but Uranus' axis is almost parallel to the ecliptic.
At the time of Voyager 2's passage, Uranus' south pole was pointed almost directly at the Sun. This results in the odd fact that Uranus' polar regions receive more energy input from the Sun than do its equatorial regions. Uranus is nevertheless hotter at its equator than at its poles. The mechanism underlying this is unknown.
There is an ongoing battle over which of Uranus' poles is its north pole. Either its axial inclination is a bit over 90 degrees and its rotation is direct, or it's a bit less than 90 degrees and the rotation is retrograde.
Uranus has been visited by only one spacecraft, Voyager 2 on Jan 24 1986. The blue-greenish color of Uranus' atmosphere is due to methane and high-altitude photochemical smog. Voyager 2 acquired this view of the seventh planet while departing the Uranian system in late January 1986. This image looks at the planet approximately along its rotational pole.
Uranus is composed primarily of rock and various ices, with only about 15% hydrogen and a little helium. It appears that Uranus does not have a rocky core like Jupiter and Saturn but rather that its material is more or less uniformly distributed.
Uranus' atmosphere is about 83% hydrogen, 15% helium and 2% methane. Like the other gas planets, Uranus has bands of clouds that blow around rapidly. But they are extremely faint. Recent observations with HST show larger and more pronounced streaks. Further HST observations show even more activity.
Uranus is no longer the bland boring planet that Voyager saw. It now seems clear that the differences are due to seasonal effects since the Sun is now at a lower Uranian latitude which may cause more pronounced day/night weather effects.