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A globular cluster is
a spherical grouping of
tens of thousands of
stars, which are tightly
bound by gravity.
They are found in the
outer reaches of spiral
and elliptical galaxies.
Globular Cluster
Like Jupiter and Saturn, Uranus is a Gas Giant and thus its visible surface is not solid.
However, it is a blue-ish colour, rather than the yellow/orange of Saturn. This is because of the methane that exists in the cloud-tops of its much colder atmosphere.
Uranus has rings, like Saturn, but they are much thinner and far more difficult to see.
Uranus was the first planet to be discovered in modern times, and was found by the English astronomer William Herschel back in 1781.
The only space-probe to pass by Uranus was Voyager 2 in 1986.
Uranus has 27 known moons (as of 2009). 22 of these are very small and most orbit close to Uranus. The other five (Miranda, Ariel, Umbriel, Titania and Oberon) are larger and further out.
| Facts and Figures | Mercury | Venus | Earth | Mars | Jupiter | Saturn | Uranus | Neptune |
| Orbital Distance (AU)1 | 0.38 | 0.72 | 1.0 | 1.52 | 5.2 | 9.45 | 19.2 | 30.06 |
| Radius (KM) | 2,440 | 6,052 | 6,378 | 3,397 | 71,492 | 60,268 | 25,559 | 24,746 |
| Mass (Earth Masses)2 | 0.055 | 0.82 | 1.0 | 0.11 | 318 | 95.2 | 14.5 | 17.1 |
| Year Length (Earth Days) | 88 | 225 | 365.25 | 687 | 11.9 Years |
29.45 Years | 84.0 Years | 164.8 Years |
| Day Length (Earth Days) | 176 | 117 | 1.0 | 1.03 | 0.41 | 0.43 | 0.75 | 0.67 |
| Surface Gravity (g)3 | 0.38 | 0.91 | 1.0 | 0.38 | 2.34 | 0.93 | 0.92 | 1.12 |
| Surface Temperature | -200 to 400 °C | 460 °C | -80 to 50 °C | -150 to 20 °C | -110 °C | -140 °C | -190 °C | -200 °C |
| Number of moons | 0 | 0 | 1 | 2 | 63 | 60 | 27 | 13 |
