Our opinion on the bland – looking planet Uranus has only changed, when we found out more about him: it has a dynamic world with some of the brightest cloud systems of our solar system and is surrounded by 11 rings. Uranus blue-green color is caused by the methane gases under its cloud layers (methane absorbs red light and reflects blue light).
Uranus was discovered in 1781 by the astronomer William Herschel, who thought it was a comet in the beginning. The seventh planet from the Sun is so far away that a complete orbit around the sun lasts 84 Earth years.
Uranus is a “gas giant”, because it has no solid surface. Uranus atmosphere is composed of hydrogen (H2) and helium (He), with a small amount of methane (CH4) and trace amounts of water (H2O) and ammonia (NH3). The major portion (at least 80%) of its mass is in a liquid core consisting of icy material (water, methane and ammonia) with high density material inside.
1986 Voyager 2 observed faint cloud movements in the southern hemisphere of Uranus, which moved at a speed of 100 to 600 km/h westward. 1998 the Hubble Space Telescope observed more than 20 bright clouds at different heights in the atmosphere of Uranus. The bright clouds are probably made of crystals of methane, which condense from warm gas bubbles from deep in the atmosphere of Uranus.
The equator of Uranus is not horizontal to the sun like the one from the other planets, but vertically. This unusual rotation might be the result of a collision with a planet-like body in the genesis time of the planet. The axis of the magnetic field of Uranus differs 60° to the equatorial axis, which is very unusual.
Uranus is so far away from the sun – although he leans to one side, one season (summer – winter) lasts over 20 years. However, the temperature between the seasons hardly changes and is near the cloud cover approximately -215 °C.
The rings of Uranus were first discovered 1977. The rings are in the equatorial plane, perpendicular to the rotation around the sun. The 10 outer rings are dark, thin and narrow, while the 11th ring is inside the other 10, is broken and diffuse. The rings of Uranus are significantly different from those of Jupiter and Saturn. If you could look through the rings behind the Uranus in the direction of the sun, you would see the fine dust between the rings.
Uranus is named after the ancient Greek god of heaven. Uranus has 27 known moons, which are almost all named after characters from the works of Shakespeare and Alexander Pope. Miranda is the strangest moon of Uranus. The high mountains and windy valleys of the moon may be the cause that the interior partially melts and material comes up from there to the surface.
| Discovery date | 1781 (William Herschel) |
| Semi-major axis | 2 872 428 701 km = 2.872 x 109 km (19.201 AU) Comparison: 19.201 x Earth |
| Perihelion | 2 741 231 369 km = 2.741 x 109 km (18.324 AU) Comparison: 18.324 x Earth |
| Aphelion | 3 003 626 033 km = 3.003 x 109 km (20.078 AU) Comparison: 20.078 x Earth |
| Diameter | 51 118 km = 5.1118 x 104 km Comparison: 4.007 x Earth |
| Circumference | 160 592 km = 1.60592 x 105 km |
| Volume | 69 142 000 000 000 km3 = 6.9142 x 1013 km3 Comparison: 63.1 x Earth |
| Mass | 86 849 000 000 000 000 000 000 000 kg = 8.6849 x 1025 kg Comparison: 14.371 x Earth |
| Density | 1.3 g/cm3 Comparison: 0.236 x Earth |
| Surface area | 8 115 600 000 km2 = 8.1156 x 109 km2 Comparison: 15.91 x Earth |
| Surface gravity | 8.43 m/s2 Comparison: Someone with 100 kg on Earth, would weigh 86 kg on Uranus. |
| Escape velocity | 76 640 km/h = 21 290 m/s Comparison: 1.904 x Earth |
| Sidereal rotation period | -0.7196 Earth days (retrograde) -17.24 hours (retrograde) |
| Orbital period (Length of a year) |
84.02 Earth years 30 687.2 Earth days |
| Average orbital speed | 24 607 km/h = 6835.2 m/s Comparison: 0.229 x Earth |
| Eccentricity | 0.047168 Comparison: 2.823 x Earth |
| Inclination | 0.770° |
| Axial tilt | 97.86° Comparison: 4.173 x Earth |
| Peripheral orbit | 17 620 000 000 km = 1.762 x 1010 km Comparison: 19.06 x Earth |
| Minimum/Maximum surface temperature |
-216 °C = 57 K Comparison: The temperature of the Earth is ~ 185/331 K |
| Composition of the atmosphere |
Hydrogen (H2), Helium (He), Methane (CH4) Comparison: The atmosphere of the Earth is mainly composed of N2 and O2. |
Moons:
Uranus has 27 known moons, and they are named after characters from the works of William Shakespeare and Alexander Pope.