Uranus

**Uranus** is the seventh planet from the Sun, Uranus is a gas giant much like Jupiter and Neptune. This ice giant is surrounded by 13 faint rings and 27 small moons as it rotates on a 90 degree angle. This unique tilt makes Uranus appear as if it's tilting on its side.

Uranus was the first planet to be found with the aid of a telescope, discovered in 1781 by astronomer William Herschel, although originally he thought it was a comet or a star. Uranus was officially classed as a planet two years later because of observations by astronomer Johann Elert Blode.

William Herschel tried to name the planet Georgium Sidus after King George III, but that name was rejected. Instead, the planet was named for Uranus, the greek god of the sky, which was suggested by Johann Blode.

## Size and Distance

Uranus is 4 times wider than Earth, with a radius of 15,759.2 miles (25,362 kilometres). Uranus would be the size of a softball if Earth was a nickel.

Uranus is 19.8 astronomical units away from the Sun, with an average distance of 1.8 billion miles (2.9 billion kilometres). One astronomical unit (abbreviated as 'AU') is the equal distance from the Sun to Earth. It takes sunlight 2 hours and 40 minutes to reach Uranus.

## Orbit and Rotation

One day on Uranus takes about 17 hours (the time it takes for Uranus to complete one rotation). The time it takes for Uranus to complete one orbit around the Sun (a year in Uranian time) takes 84 Earth years (30,687 Earth days).

Uranus' equator is tilted at a right angle to its orbit, with a tilt of 97.77 degrees - possibly the result of a an Earth-like object long ago. This unique tilt causes the most extreme season in the solar system. For a quarter of the year, the Sun shines directly over each pole plunging the other half of the planet into a 21-year-long winter.

Uranus is also one of two planets that tilts on its side instead of upright (the other being Venus).

## Structure

Uranus is one of two ice giants located in the outer solar system (the other being Neptune). Most of the planet's mass, about 80%, is made up of a hot dense fluid of "icy" materials - water, methane and ammonia - above a small rocky core. At the core, temperatures rise up to 4,982 degrees celsius.

Uranus has a slightly larger diameter than Neptune, yet it's smaller in mass. it is the second least dense planet in the solar system (the least dense being Saturn).

Uranus gets its blue-green colour from methane gas in the atmosphere. When sunlight passes through the planet's atmosphere, it is reflected back out by Uranus' clouds. Methane gas absorbs the red portion of the light, resulting in a blue-green colour.

## Formation

When the solar system settled into its current state, about 4.5 billion years ago, gravity pulled swirling gas and dust to form the ice giant. Like Neptune, Uranus likely formed closer to the Sun but was pushed to the outer solar system about 4 billion years ago, where it's currently the seventh farthest planet from the Sun.

## Surface

As an ice giant, Uranus doesn't have a true surface. The planet is mostly made up of swirling fluids. Whilst a spacecraft would have nowhere to land, it wouldn't be able to fly through the atmosphere unscathed either. The extreme pressures and temperatures would destroy a metal spacecraft.

## Atmosphere

Uranus' atmosphere is mostly composed of hydrogen and helium, with a small amount of methane and traces of water and ammonia. The methane gives Uranus its blue colour.

While Voyager 2 only saw swirls of clouds, A Great Dark Spot and a small dark spot was spotted during its flyby. This potentially proves that Uranus has dynamic clouds.

Uranus' atmosphere, with a minimum temperature of -224.2 degrees celsius makes it even colder than Neptune in some places on the planet.

Wind speeds can reach up to 560 miles per hour (900 kilometres per hour) on Uranus. Winds are directed at the equator, blowing the reverse direction of the planet's rotation. Closer to the poles, the winds follow Uranus' rotation.

## Magnetosphere

Uranus has an unusually, irregularly shaped atmosphere. Magnetic fields are typically in alignment with the planet's rotation, but Uranus' magnetic field has tipped over; the magnetic axis is tilted at nearly 60 degrees from the planet's axis of rotation and is also offset from the centre of the planet 1/3 of the planet's radius.

Auroras on Uranus don't occur at the line of the poles (like they are on Earth, Jupiter and Saturn) due to the lopsided magnetic field.

The tail of the magnetosphere behind Uranus opposite the Sun extends into space for millions of miles. Uranus' sideways rotation twists the magnetic field lines.

## Rings

Uranus has two faint sets of rings. The inner rings consist of dark grey, narrow. There are two outer rings, the innermost one is reddish like dusty rings located outside the solar system and the outer ring is blue like Saturn's E ring.

In order of increasing distance from the planet, the rings are called Zeta, 6, 5, 4, Alpha, Beta, Eta, Gamma, Delta, Lambda, Epsilon, Nu and Mu. Some of the larger rings are surrounded by fine belts of dust.

## Moons

Uranus has 27 known moons in orbit. Whilst most of the satellites are named after Greek or Roman mythology, Uranus' moons are unique after being named after William Shakespeare and Alexander Pope characters.

Uranus' inner moons appear to be made of half ice water and half rock. The compositions of the outer moons are still unknown, but are likely captured asteroids caught in Uranus' orbit.

## Human Life

Uranus' extreme temperatures and pressures make human life very unlikely to colonise on this planet.