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History of Astronomy
See Also:
Solar System - Wikipedia, the free encyclopedia
Asteroids, Comets and Meteors
The Planet Uranus
William Herschel accidentally discovered the planet Uranus in 1781. Uranus had been seen many times before, but it had always been dismissed as a star.
Uranus is made up mostly of hydrogen and helium like Jupiter and Saturn, but it has higher concentrations of heavy elements. Our closest look at Uranus was given to us by Voyager 2 in 1986.
Uranus is one of the four "Giant Gas Planets" (the other three are Jupiter, Saturn, and Neptune). The rings around Uranus are made up of rock, rather than ice like those of Saturn. We do know that there are five large moons and at least 10 smaller moons. The rotational period of Uranus is a little over 17 hours, and its orbital period is 84 years.
Uranus appears to be a giant blue featureless ball. Voyager 2 got relatively close to Uranus and could not pick up any distinguishable features. It is believed that the upper atmosphere of Uranus has a high-level petrochemical haze that probably obscures features lower in the atmosphere. The blue color is caused by methane gas in the atmosphere. Methane gas absorbs red and orange light, which leaves more blue light.
Voyager 2 confirmed that Uranus has a magnetic field. The field is more than 50 times stronger than that of Earth and is tilted about 60 degrees.
The latest scientific data suggests that Uranus is surrounded by at least five rings. The brightest ring is called the Epsilon ring. Voyager 2 located two small shepherd moons for it, one just inside and one just outside. These two shepherd moons have been named Ophelia and Cordelia.
The most interesting moon that circles Uranus is Miranda. Miranda isn't very big, but it has some very interesting geological features. |
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More articles:
Telescope Buying Guide
The Nebulous Jesus
The Antikythera Mechanism
The Antikythera Mechanism
New Telescopes Planned For Moon
Binoculars for Astronomy
Mirrors and Lenses
Many people believe that the main function of a telescope is just to make distant celestial objects appear bigger so that astronomers (even amateur astronomers) can see them better, but that really is a misconception. The fact is that telescopes work by gathering light. Magnifying distant objects is secondary. Telescopes gather light basically in two ways: through the use of lenses, and through the use of mirrors. The third way that telescopes gather light is by using a combination of lenses and mirrors.
A telescope that gathers light through the use of a lens is called a refractor telescope. The truth is that how much you spend on a refractor telescope is the determining factor of how well you will be able to see celestial objects. Inexpensive refractor telescopes (2.4 inch) have not-so-good optics and low light grasp. High-end refractor telescopes (3.5 inch) have almost perfect optics and much, much better light grasp.
Telescopes that gather light through the use of a mirror are called reflector telescopes. Refractors cost less per inch of aperture. They are less costly to manufacture because there is only one optical surface, and they lend themselves well to different designs and uses. Also, because the light doesn't have to pass through glass, the images are basically color free. Probably the best telescope for a novice astronomer is the Newtonian reflector. The cost factor is a plus for the refractor telescope, but the corresponding minus (there always is one) is that the primary mirror is ground to a concave shape, so the outside zone has a little longer focal length than the inner zone.
A catadioptic telescope is a compromise between a refractor and a reflector, because both lens and a mirror are used. Catadioptic telescopes are portable. They do not cost as much as a high-quality refractor telescope, but they cost a little more than a good-quality reflector telescope. Still, they are the best of both worlds.
Related Topics: The First Seven Astronauts,
The Demotion of Pluto, The Planet Jupiter
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