Uranus is the seventh planet of the sun. This cold and windy planet has the fourth-largest planetary mass and third-largest diameter in the solar system. This ice giant has 27 small moons and is very similar to Neptune.
Uranus Profile
Interesting Uranus Facts
- It is the seventh planet in the solar system.
- It is the third-largest planet in the solar system in terms of size.
- Uranus is 2.871 billion kilometers away from the sun.
- Uranus formed around 4.5 billion years ago.
- It takes 30,688 days i.e. approximately 84 years to revolve around the sun.
- It has a rotation period of 17 hours and 14 minutes.
- It has a diameter of 51,118 kilometers.
- Uranus is known to have 13 rings.
- It has 27 moons.
- It has been named after the Greek deity of the sky who was the grandfather of Zeus i.e. Jupiter in Roman mythology.
- It is often called an ‘ice giant‘.
- Uranus is one of the only two planets in the solar system, along with Venus that orbits the sun in a clockwise direction.
- Uranus is fifteen times larger than the Earth.
- All of Uranus’ moons are named after characters from Shakespearean plays.
- It was the first planet to be found with the help of a telescope.
- The light of the sun takes 2 hours and 40 minutes to reach Uranus.
- Uranus has only been visited by one spacecraft i.e. NASA’s Voyager 2.
- Uranus is sometimes considered a ‘geometric nightmare‘ due to its unusual magnetic fields.
History
Uranus formed about 4.5 billion years ago along with all the other planets of the solar system by the combination of dust and gas. Uranus was discovered by William Herschel in 1781. However, he presumed it to be a comet.
People had seen the planet before in the night sky but always considered it as a mere star in the sky. The earliest observations of the planet known to humans were recorded by Hipparchus as early as 128 BC.
Anders Johan Lexell became the first person to observe and compute the orbit of this object. Later on, it was concluded by Bode that the orbit Uranus had the nature of the orbit of a planet rather than a comet.
William initially named it Georgium Sidus meaning the Georgian planet. It soon goes recognized and accepted as a planet. It took almost 70 years for people to agree upon a name for the planet.
It was in 1850 that people started to use the term ‘Uranus’. The planet is named after the Greek deity of the sky. Uranus was the father of Cronus i.e. Saturn and the grandfather of Zeus i.e. Jupiter. It is the only planet that has been named directly after a Greek god.
Appearance
Uranus is often called as an ice giant along with the planet Neptune. Since it is mostly made up of ice and gas. It has a greenish appearance, but this green color is artificial. Actually, Uranus has a pale blue color and its surface appears to be smooth.
It is also believed that Uranus can be colorful like Jupiter, but its clouds hide its real appearance. The color of the planet is such because due to the presence of methane clouds above it. This is one of the reasons why Uranus is said to be an unusual planet.
Uranus has a set of rings. 13 rings of the planet are known currently. The rings of the planet are vertical unlike those of Jupiter or Saturn. The outermost of the rings are of bright blue color. The rings become dimmer as we approach the planet.
Uranus appears to rotate on its side when viewed from the Earth. The ring system is however very dark, just like Jupiter and can only slightly be seen. Only nine of Uranus’ rings are visible from the Earth. Near the southern part of the planet, clouds are also visible.
Size
Uranus is the seventh object from the sun. It is about 2.9 billion km away from the sun. It is the third-largest planet in the solar system in terms of radius and the fourth largest in terms of mass. The planet is a little larger in size than Neptune. However, Neptune has a larger mass.
Surface
Uranus along with Neptune is an ice giant. This means that it does not have any well-defined surface. It is mostly composed of liquids. The surface area of Uranus is 8.083 billion km².
Composition
Uranus is quite similar to Neptune when it comes to composition. The two planets, Uranus and Neptune, are often referred to as ‘ice giants’. The equatorial diameter of Uranus is 51,118 km. The intensity of light on Uranus is very small. It is about 1/400th the intensity of light on the earth.
The temperature of the planet is known to be as low as -270° C. The wind speeds on the planet are as high as 1,770 kilometers per hour.
Magnetic field & Gravitational Forces
Much like the other planets in the solar system, Uranus has a magnetic field that is generated by convection currents in its interior. However, Uranus has an unusual magnetosphere. As the planet rotates on its side, the magnetic field of Uranus is lopsided.
The field is not centered and is tilted 60° from its axis. Hence, the magnetic field tumbles asymmetrically. Uranus undergoes a rapid rotation change in orientation and field strength. This leads to an open-close-open-close situation.
This means that the magnetic field of Uranus is like a light switch i.e. it turns on and off every day as it rotates with the planet every 17 hours and 15 minutes as well. Hence, Uranus has been described as a ‘geometric nightmare’.
It is the second least dense planet with an average density of 1.27 grams per centimeter cube, the first being Saturn. About 80% of the planet is made up of water, ammonia, and methane. Because of high pressure, it has a small core with a temperature of nearly 9000°F or 4982°C.
Orbit & Rotation
It takes nearly 84 years to revolve around the run and 17 hours and 14 minutes to rotate about its axis. Uranus rotates at an angle of nearly 90°. The cause of this tilt is not clearly known but is believed to be a collision with an object as big as the earth.
This tilt makes the planet appear to spin on its side. Hence, Uranus is a unique planet. The tilt is the reason why Uranus has an unusual seasonal cycle.
The sun shines over each pole for 21 years. In between, there are 42 years of darkness. Since Uranus is a gas giant, it does not have a definite surface i.e. no spacecraft’s can land on it. No spacecraft would even be able to fly through the atmosphere of the planet because of the high temperatures.
Atmosphere
Uranus has a thick envelope around its surface. The planet’s atmosphere can be divided into three parts.
Troposphere
The first layer is the troposphere. It extends from the height of -300 km to 50 km with a pressure of 100 to 0.1 bar. It is the lowest and the densest part of the Uranus atmosphere and has a very complex cloud structure.
Stratosphere
The second layer is the stratosphere. The stratosphere spans the distance from 50 km to nearly 4000 km. Its atmospheric pressure varies from 0.1 to 10−10 bar.
Thermosphere
The third layer is called the thermosphere. The thermosphere spans from 4000 km to as far as 50,000 km from the surface.
The planet has no mesosphere. Most of the atmosphere is composed of hydrogen and helium. The third most abundant substance in the atmosphere of the planet is methane.
Moons
Uranus is known to have 27 moons. All of the planet’s moons are named after characters from plays written by William Shakespeare and Alexander Pope, unlike other planets whose moons are mostly named after Roman or Greek gods or mythological characters.
The moons of Uranus are divided into three groups. The first group consists of thirteen inner moons. The second group consists of five major moons. The third group consists of nine irregular moons.
The largest moon of Uranus is Titania. It was one of the first two moons of the planet to be discovered, along with Oberon. The two moons were discovered by William Herschel in 1787. Titania is the eighth largest moon in the solar system. It is close to 1580 km in diameter.
The next two moons to be discovered were Arial and Umbriel. They were discovered by William Lassell in 1851. Miranda, the last of the five major moons were discovered by Gerard Kuiper in 1948. Miranda is also the smallest of the five major moons.
The last moon of the planet to be discovered by now is Margaret. It was discovered in 2003. The inner moons of Uranus are composed of half rock and half water ice. Not much is known about the composition of the outer moons of the planet. They are believed to be asteroids that have been captured.
Rings of Uranus
Uranus is known to have 13 distinct rings. They are mostly made up of dust particles and are very thin, each ring being only a few km thick. The rings of Uranus are believed to be about 600 million years old, unlike the planet which is 4.5 billion years old.
They were probably formed by the bits and pieces of other moons that were shattered due to collision or gravity. In increasing order of their distance from the planet, they are named as Zeta, 6, 5, 4, Alpha, Beta, Eta, Gamma, Delta, Lambda, Epsilon, Nu and Mu.
Just like the moons, the rings of Uranus are divided into three groups. The first group consists of 9 main rings that are narrow. The second group consists of two dusty rings and the third group of two outer rings.
The nine main rings are a set of narrow rings that are dark grey in color. The Epsilon ring is the brightest and densest ring in the Uranus ring system. The exact thickness of the ring is not known. However, it is estimated to be about 150 m.
There are two dusty rings. One of them is reddish while the other one is blue, similar to the rings of Saturn. The rings of Uranus were discovered in 1977, nearly two hundred years after the planet was discovered. They were discovered by James L. Elliot, Edward W. Dunham, and Douglas J. Mink. However, William Herschel claimed to have seen the rings, there was no scientific evidence as the rings of the planet are very thin.
Exploration
Uranus has been visited by only one spacecraft which is Voyager 2 by NASA. Voyager 2 flew by all the giant planets due to their suitable alignment. It took around nine years for the spacecraft to travel from the Earth to Uranus. Voyager 2 made its closest approach to the planet more than 30 years ago in 1986.
Voyager 2 provided a lot of details and information about the planet in just six hours. It discovered 10 new moons and two new rings, studied the cold atmosphere of the planet and observed its ring system in detail. It also provided photographic details about Uranus’. It studied the nine rings known to man at that time.
The study was of great detail and distinction. The spacecraft helped us arrive at the conclusion that the rings of Uranus are relatively young and distinct from those of Jupiter and Saturn. The presence of the unusual magnetic field of the planet was also discovered by Voyager 2.
A lot of proposals for missions like flybys, orbiters and even spacecraft to be sent to Uranus have been made till 2018 but none of them have been approved yet. Thus, as of now, the only other sources of information about the planet are telescopes, especially the Hubble Space Telescope.
Potential for Life in Uranus
As of today, no evidence of life has been found on the planet Uranus. The conditions on the planet are too extreme to sustain life. Most importantly, Uranus doesn’t have the necessary gases or substances for life to thrive. It also does not have a definite surface. This means that it is impossible to stand on the surface of Uranus.
The temperature, pressure and other characteristics of the planet are also too extreme, volatile and not suitable to conduct life. It is very unlikely that life ever existed on Uranus in the past or could ever exist in the future as well.
Uranus in Pop Culture
In the field of astrology, Uranus is the ruling planet of the zodiac sign Aquarius. The chemical element of Uranium is named after the planet Uranus. Other than this, Uranus has been mentioned in numerous books, TV shows, films, and video games.
Timeline
- 1781: Uranus is discovered by William Herschel
- 1787: Titania and Oberon, 2 of Uranus’ moons are discovered by William Herschel
- 1787-1948: Five more moons are discovered
- 1977: Rings of Uranus are discovered
- 1986: Voyager 2 flies by Uranus
- 1994: Uranus photographed by Hubble Space Telescope
- 2005: 2 new moons and 2 new rings are discovered by Hubble Space Telescope
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