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Uranus ( just the facts - a article written in 2007)
The Planet Uranus, named for the Greek word, meaning "heaven" or "sky" is the seventh planet from the Sun. It is a gas giant, the third largest by diameter & fourth largest by mass. It is named after Uranus, the Greek god of the sky & progenitor of the other gods. Its symbol is either (astrological) or (astronomical). The first symbol derives from the name of its discoverer, William Herschel. The second symbol is a combination of the devices for the Sun & Mars, as Uranus was the personification of heaven in Greek mythology, dominated by the light of the Sun & the power of Mars. It is also the alchemical symbol of platinum.
Uranus
is the first planet discovered in modern times. Sir William Herschel formally
discovered the planet on March 13, 1781; the other planets (from Mercury out to
Saturn) have been known since ancient times, since they are visible to the naked
eye. Uranus' discovery expanded the boundaries of the solar system for the first
time in modern human history. It was also the first planet discovered using technology
(a telescope) rather than the naked eye.
Discovery & naming
Uranus
is the first planet to be discovered that was not known in ancient times; although
it had been observed on many previous occasions, it was often mistakenly identified
as a star. The earliest recorded sighting was in 1690 when John Flamsteed catalogued
Uranus as 34 Tauri. Flamsteed observed Uranus at least six more times. The record
belongs to a French astronomer, Pierre Lemonnier, who observed Uranus at least
twelve times between 1750 & 1771, including on four consecutive nights. (Lemonnier
is often called careless or even "sloppy" for this, but it is important
to know that he realized 9 of these within a short time of Herschel's discovery
& most of his observations occurred at the stationary point in Uranus' orbit.)
Sir William Herschel discovered the planet on March 13, 1781, but reported it on April 26, 1781, as a "comet."
On the 13th of March, 1781, between ten & eleven o'clock at night, while Herschel was examining the small stars near H Geminorum with a seven-foot telescope, bearing a magnifying power of two hundred & twenty-seven times, one of these stars seemed to have an unusual diameter; & it was, therefore, thought to be a comet. It was under this denomination that it was discussed at the Royal Society of London. But the researches of Herschel & of Laplace showed later that the orbit of the new body was nearly circular, & Uranus was consequently elevated to the rank of a planet. Herschel originally named it Georgium Sidus (George's Star) in honour of the greedy unelected King George III of Great Britain, but I suppose many things are named after unpalatable people, & this name could be called a insult. (Like in the fanous joke, I can see Uranus, your anus the planet your anus, ho ho, or that joke in the Sweeney when he said, have'nt you heard, to his wife, very sexistyly galileo found out the world does not revolve around Your Anus,) (c.f. American poet Elizabeth Graeme Fergusson's "Upon the Discovery of the Planet..." about the event). When it was pointed out that sidus means star & not planet, Herschel rebaptised it the Georgian Planet. This name was not acceptable outside of Britain. Lalande proposed in 1784 to name it Herschel, at the same time that he created the planet's (astrological) symbol ("a globe surmounted by your initial"); his proposal was readily adopted by French astronomers. Prosperin, of Uppsala, proposed the names Astraea, Cybele, & Neptune (now borne by two asteroids & another planet). Lexell, of St. Petersburg, compromised with George III's Neptune & Great-Britain's Neptune. Bernoulli, from Berlin, suggested Hypercronius & Transaturnis. Lichtenberg, from Göttingen, chimed in with Austräa, a goddess mentioned by Ovid (but who is traditionally associated with Virgo). The name Minerva was also proposed. Finally, Bode, as editor of the Berliner Astronomisches Jahrbuch, opted for Uranus, after Latinized version of the Greek god of the sky, Ouranos; Maximilian Hell followed suit by using it in the first ephemeris, published in Vienna & computed by the Benedictine priest Placidus Fixlmillner. The earliest publication to include Uranus in its title was in 1823. The name was in use in Germany at least as far back as 1791, however. Examination of earliest issues of Monthly Notices of the Royal Astronomical Society from 1827 shows that the name Uranus was already the most common name used even by British astronomers by then, & probably earlier. The name Georgium Sidus or "the Georgian" was still used infrequently (by the British alone) thereafter. The final holdout was HM Nautical Almanac Office, which did not switch to Uranus until 1850.
The stressed syllable in the name is properly the first, antepenultimate syllable, since in Latin the penultimate vowel a is short (uranus) & in an open syllable, & such syllables are never stressed in Latin. The historically correct pronunciation of the name by English-speakers is therefore. The historically incorrect pronunciation , with stress on the second syllable & a "long a" (uranus) have become very common, however, perhaps through the influence of the related adjective "Uranian" (always pronounced in a way of the similarly-pronounced name of the element uranium.
In the Chinese, Japanese, Korean, & Vietnamese languages, the planet's name is literally translated as the sky king star, while in India it is named Aruna , the charioteer of the sun god Surya in Hindu mythology.
Physical characteristics
Composition
Uranus
is composed primarily of gas & various ices. The atmosphere is about 83 percent
hydrogen, 15 percent helium, 2 percent methane & traces of acetylene. The
interior is richer in heavier elements, most likely compounds of oxygen, carbon,
& nitrogen, as well as rocky materials. This is in contrast to Jupiter &
Saturn which are mostly hydrogen & helium. Uranus (like Neptune) is very much
similar to the cores of Jupiter & Saturn without the massive fluid metallic
hydrogen envelope. Uranus' cyan color is due to the absorption of red light by
atmospheric methane. Surface temperature on Uranus' cloud cover is approximately
55 K (-218 °C or -360 °F).
Axial tilt
One of the most distinctive
features of Uranus is its axial tilt of ninety-eight degrees. Consequently, for
part of its orbit one pole faces the Sun continually while the other pole faces
away. At the other side of Uranus's orbit the orientation of the poles towards
the Sun is reversed. This gives each pole 42 years of continuous sunlight, followed
by 42 years of darkness. Between these two extremes of its orbit, particularly
at the equinoxes, the Sun rises & sets around the equator normally. Uranus
will reach its next equinox around December 2007, & not again until 2049.
Season, Northern Hemisphere Year Season, Southern Hemisphere
Winter
Solstice 1902, 1986 Summer Solstice
Vernal Equinox 1923, 2007 Autumnal Equinox
Summer Solstice 1944, 2028 Winter Solstice
Autumnal Equinox 1965, 2049
Vernal Equinox
At the time of Voyager 2's passage in 1986, Uranus' south pole was pointed almost directly at the Sun. The labelling of this pole as "south" uses the coordinate definitions currently endorsed by the International Astronomical Union, namely that the north pole of a planet or satellite shall be the pole which points above the invariable plane of the solar system (regardless of the direction the planet is spinning) . A different system is sometimes used, defining a body's north & south poles according to the right-hand rule in relation to the direction of rotation . In terms of this latter coordinate system it was Uranus' north pole which was in sunlight in 1986. On page 47 of the September 2006 issue of the Sky at Night magazine, Patrick Moore, commenting on the issue, sums up "take your pick!"
One result of this orientation is that the polar regions of Uranus receive a greater energy input from the Sun than its equatorial regions. Uranus is nevertheless hotter at its equator than at its poles, although the underlying mechanism which causes this is unknown. The reason for Uranus' extreme axial tilt is also not known. It is speculated that during the formation of the Solar System, an Earth sized protoplanet collided with Uranus, causing the skewed orientation.
It appears that Uranus' extreme axial tilt also results in extreme seasonal variations in its weather. During the Voyager 2 flyby, Uranus' banded cloud patterns were extremely bland & faint. Recent Hubble Space Telescope observations, however, show a more strongly banded appearance now that the Sun's overhead position relative to Uranus is approaching Uranus' equator. By 2007 the Sun will be directly over Uranus' equator.
Magnetic field
Uranus's magnetic field is peculiar
since it is not originating from the geometric center of the planet & is tilted
almost 60° from the axis of rotation. It is probably generated by motion at
relatively shallow depths within Uranus. Neptune has a similarly displaced magnetic
field, which suggests the magnetic field is not necessarily a consequence of Uranus'
axial tilt. The magnetotail is twisted by the planet's rotation into a long corkscrew
shape behind the planet. The magnetic field's source is unknown.
Explanation
for bland atmosphere
The internal heat of Uranus is lower than that of Jupiter
& Saturn. Both Jupiter & Saturn radiate more energy than they receive
from the Sun. This causes many powerful convection currents to form in the atmosphere.
On Uranus that heat source is much lower due to its lower mass, with the temperature
of its core roughly 7000 K compared to 30 000 K at Jupiter's core & 18 000
K at Saturn. The convection currents formed in the Uranian atmosphere are not
as strong & hence it lacks the atmosphere banding of the larger gas giants.
However, as stated above, the weather patterns of Uranus do vary with season,
being more pronounced at the equinoxes than at the solstices.
Cloud
features
For a short period in Autumn 2004, a number of large clouds appeared
in the Uranian atmosphere, giving it a Neptune-like appearance. On August 23,
2006, researchers at the Space Science Institute (Boulder, CO) & the University
of Wisconsin observed a dark spot on Uranus' surface, giving astronomers more
insight into the planet's atmospheric activity.
Rings of Uranus
Uranus has a faint planetary ring system, composed of dark particulate matter
up to ten meters in diameter. This ring system was discovered March 10, 1977 by
James L. Elliot, Edward W. Dunham, & Douglas J. Mink using the Kuiper Airborne
Observatory. The discovery was serendipitous; they planned to use the occultation
of the star SAO 158687 by Uranus to study the planet's atmosphere. However, when
their observations were analyzed, they found that the star had disappeared briefly
from view five times both before & after it disappeared behind the planet.
They concluded that there must be a ring system around the planet; it was directly
imaged when Voyager 2 passed Uranus in 1986.
In December 2005, the Hubble Space Telescope detected a pair of previously unknown rings. The largest is located at twice the distance from the planet than the previously known rings. The new rings are so far from the planet that they are being called Uranus' "outer" ring system. Hubble also spotted two small satellites. One, Mab, shares its orbit with the outermost newly discovered ring. These two rings bring the total number of Uranus rings to 13.
In April 2006, images of the new rings with the Keck Observatory yielded the colors of the outer rings: one was blue & the other red. A marked similarity to the colorful E & G rings of Saturn may be a coincidence, or it may be related to a similar causal mechanism. The source of the rings' colors are still an area of active research. The planet's inner rings appear grey.
Exploration
NASA's
Voyager 2 is the only spacecraft to have visited the planet & no other visits
are currently planned. Launched in 1977, Voyager 2 made its closest approach to
Uranus on January 24, 1986, before continuing its journey to Neptune.
Uranus'
natural satellites
Uranus has 27 known natural satellites. The names for
these satellites are chosen from characters from the works of Shakespeare &
Alexander Pope. The five main satellites are Miranda, Ariel, Umbriel, Titania
& Oberon.
The Uranian satellite system is the least massive among the gas giants; indeed, the combined mass of the five major satellites would be less than half that of Triton alone. The moons are low-albedo, ice-rock conglomerates.
The
main Uranian moons
Miranda IPA:
Ariel IPA:
Umbriel IPA:
Titania IPA:
Oberon IPA:
The brightness of Uranus is between magnitude +5.5 &
+6.0. Thus, under dark sky conditions it can be seen with the naked eye as a faint
disk. From Earth, it has a diameter of four arcseconds. It is an easy target with
binoculars. In larger amateur telescopes with an objective diameter greater than
12" (30 cm), the planet appears as a pale blue disk with distinct limb darkening.
The larger satellites, Titania & Oberon, may be visible. Because of its faintness
& slow apparent motion, it was never recognised as a planet by ancient astronomers.
As
the planet approaches its 2007 equinox, dynamic cloud activity is developing.
Most of the activity requires Hubble Space Telescope or large telescopes with
adaptive optics to be detectable. However, some features may become bright enough
to be seen with moderately large amateur telescopes. In 2006, a Dark Spot was
detected in visible-wavelength Hubble images, suggesting that the atmosphere of
Uranus near equinox is becoming more like that of Neptune.
Here are many great space sites
An Index with links to almost all our sites.
A Picture of Jupiter, & a Picture of Florida from Space
A Top picture of a Space Shuttle taking off A Top picture of Stars A Nebula
SOLAR SYSTEM RECORD BREAKERS, facts like the tallest mountain for the planets
A site saying the 10 most famous aliens ever
A Clock saying how many people have landed on each planet in our Solar System
Jokes to say to aliens that are offending you
Joke names for aliens, our worst Space site
A List of space associated TV programmes & Movies
http://www.lonympics.co.uk/Olympus Mons.htm Tallest mountain, & volcano in the solar system, & Mars.
A Picture of Buzz Aldrin on the Moon
What would happen if Marsians invaded
A Multiple Choice Quiz on Space
The Moon Deimos The Moon Phobos
Some interesting facts about Space
How Many people have landed on each of our Planets see, in this space clock
A list of Planets that could be colonised by humanity
Some plans for colonising Venus
Jupiter
- the facts
The Moon - the facts
A Quiz on space related TV & movies
The
facts on Space Stations Jodrell
Bank the facts
Ganymede
the facts The Facts on the
Moon Europa
Asteroids
- the facts The Kuiper
Belt - the facts
The
Planet Pluto - the facts Space
- the facts
The Milky
Way - the facts Star Trek -
the facts
The Solar System - just the facts
The
facts on the first Extra Solar planet to be known about by Humans PSR B1257 +
12, the first planet known, of outside our Solar System,
The
Galaxy andromeda The Star
Eta Carinae
Moon Buggies
- the facts
Extrasolar
plantes the facts
The
Planet Mercury - the facts
The
Planet Neptune - the facts
More
records & amazing facts to do with the Solar System, & space & the
Universe
Some ideas for stories, & movie ideas I have had, including some on space
One
of our sites on space in French The
same site in Spanish
A 1 move snippet game, a game where you are 1 space nation fighting another. in Space armageddon
The Entrance to the INTERNET SAFARI, with real animals, most of us had never seen before.
Global Geography, sites like what are the 10 largest English speaking countries, 10 largest Celtic cities, biggest forests, volcanoes,
SOLAR SYSTEM RECORD BREAKERS, facts like the tallest mountain for the planets
Another great page on space records
Which are the 10 most powerful countries in 2008___
10 Biggest Banks Histories Famous Gates Famous Walls Quizzes Famous Roads Internet Sea Safari, The Most Powerful Countries Ever