= || URANUS
|| || “THE BLUE GAS GIANT" ||
=

By DUNCAN BOYES AND TOM BRINK
CONTENTS
  • Introduction

  • When was Uranus Discovered?

  • Position and size

  • Composition and appearance

  • Clouds, Rings and Moons

    • Clouds

    • Rings

    • Moons

  • Tilt of the rotational axis of Uranus

  • Temperature on Uranus

  • Visits to Uranus

  • Bibliography



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INTRODUCTION

Uranus is known as the blue gas giant and in many Asian languages, it is translated into “Sky king star”. In the past Uranus was considered to be a boring blue planet. Not much was known about the seventh planet from the Sun. In the last two decades, however, scientists have proved that this planet has many features which make it both beautiful and unique.


WHEN WAS URANUS DISCOVERED?

Most of the planets are visible to the naked eye and were known in ancient times. Uranus was the first planet discovered after the telescope was invented. On March 13, 1781, an English astronomer named William Herschel found the planet and named it Georgium Sidus (George's Star) after King George III of England .After Herchel’s death the planet’s name was changed to Uranus, after the Greek god of the sky in Latin. It is the only planet whose name came from a person in Greek mythology instead of Roman mythology.

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POSITION AND SIZE

Uranus is the seventh planet from the Sun and the third largest. Uranus is bigger in diameter but lighter in mass than Neptune.

  • Diameter: 51,118 km

  • Density: 1.29 g/cm3

  • Mass: 8.686 x 1025 kg

  • Volume: 6.995 x 1013 km3

  • Distance from the Sun: 2,870,990,000 km from Sun Diameter

Uranus is so far from the sun that it takes 84 years to complete one orbit!

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COMPOSITION AND APPEARANCE

Uranus is one of the many gas giant planets. The others are Jupiter, Saturn, and Neptune. Uranus is mostly made up of rock and various ices, with only about 15% hydrogen and a small amount of helium. Uranus doesn’t have a rocky core like Jupiter and Saturn but instead its material is more or less evenly distributed.

Uranus' atmosphere has about 83% hydrogen, 15% helium and 2% methane. There are also traces of water and ammonia. The planet's atmospheric details are very difficult to see in the light.

Uranus gets its blue and green colour from methane gas. The Sun’s light is reflected from Uranus's cloud tops, which lie beneath a layer of methane gas. As the reflected sunlight passes back through this layer, the methane gas absorbs the red portion of the light, allowing the blue portion to pass through and resulting in the blue and green colour thatwe see.


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CLOUDS, RINGS AND MOONS

Clouds

Like all the other gas planets, Uranus has extremely long stretches of clouds that blow around rapidly, but are extremely faint and quiet. The clouds of Uranus are composed of methane crystals. They are found very low in the atmosphere, and are very difficult to see below the smog and haze from the planet.


Rings

Uranus has rings like the other gas planets. There are 13 known rings, all very faint. The brightest is known as the Epsilon ring. Uranus has the second most dramatic set of rings in the Solar System. Unlike Saturn’s particles which are made of bright ice, the rings of Uranus are very dark. They’re also narrow, only measuring a few km wide. Astronomers think that the rings of Uranus are very young, and probably formed relatively recently, and not with the planet.

Because of the planet's unusual orientation, Uranus's rings are perpendicular to its orbital path about the sun. The ten outer rings are dark, thin, and narrow, while the 11th ring is inside the others and is broad.

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Moons

Uranus has 27 known moons and these moons are very light in weight. If you could add up all their masses, they would only be less than half the mass of Triton, Neptune’s largest moon. Uranus’s largest moon is Titania with a radius of only 788.9 km which less than half that of our Moon.

The Titania and Oberon were discovered by William Herschel in 1787. Ariel and Umbriel were discovered by William Lassell in 1851. John Herschel (William Herschel's son) gave the four then known moons their names in 1852. In 1948 Gerard Kuiper discovered the moon Miranda.

All of the planets' moons seem to be made up of about 50% water ice, 30% rock, and 20% carbon and nitrogen materials.

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TILT OF THE ROTATIONAL AXIS OF URANUS

The planet's most extraordinary feature is the tilt of its rotational axis. The angle of the tilt of Uranus is 97.9 degrees. This means that Uranus orbits the Sun on its side. Its south pole is pointed towards Earth. 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.It alternately has its north pole and its south pole turned towards the sun!

Actually, there's an ongoing battle over which of Uranus' poles is its north pole!



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TEMPERATURE ON URANUS

It is the 7th planet from the Sun, orbiting at a distance of 2.88 billion km. Even though Neptune is further from the sun, Uranus is the coldest planet in the solar system. But there’s something really strange about Uranus – it’s really cold. Unlike the other large planets in the Solar System, Uranus actually gives off less heat than it absorbs from the Sun. The other large planets have tremendously hot cores, and radiate infrared radiation. But something made the core of Uranus cool down to the point that it doesn’t radiate much heat. The average temperature is -197.15 C.

Even though Uranus is tipped on its side and experiences seasons that last over 20 years, the temperature differences on the summer and winter sides do not differ greatly because the planet is so far from the sun. Near the cloud tops, the temperature of Uranus is -216 degrees Celsius.

VISITS TO URANUS

Uranus has been visited by only one spacecraft, Voyager 2 on January 24 1986. It came within 81,000 km of the surface of Uranus. It took thousands of photographs of Uranus and its moons. No other spacecraft have ever been sent towards Uranus, and there are no plans to send any more.



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BIBLIOGRAPHY
  1. en.wikipedia.org/wiki/Voyager_2

  2. The Young Astronomer Harry Ford, Dorling Kindersley

  3. Eye Witness Guides, Astronomy, Dorling Kindersley

  4. planetary.org/explore/topics/uranus/facts.html -

  5. The Illustrated Guide to the Night Skies, Robin Kerrod, Headline Publishers

  6. science.nationalgeographic.com/science/space/.../uranus-article.html -

  7. www.aerospaceguide.net/planeturanus.html

  8. www.nasa.gov/voyager/

  9. www.universetoday.com/19279/10-interesting-facts-about-uranus/end.jpg