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Asteroids, Comets and Meteors
The Hubble Space Telescope
The Hubble Space Telescope is a wonder of engineering and ingenuity. The idea for building a telescope in space that could see far beyond our own solar system was conceived in 1962 by the National Academy of Sciences in the United States. It wasn't until 1977 that the Congress of the United States finally voted to actually fund the project.
The Hubble telescope is named for Edwin P. Hubble. Hubble was a trailblazing astronomer who was born in 1889 and died in 1953.
The Hubble telescope has given astronomers unprecedented access to views of deep space. It has actually revolutionized the science of astronomy in many ways. The Hubble Telescope can "see" far beyond our own solar system and beyond our own galaxy into deep space, where fledgling galaxies are only just beginning to form.
The Hubble telescope wasn't launched until 1990 even though it was originally scheduled to launch in 1983. The launch experienced many delays, the most notable of which was the space shuttle Challenger disaster in 1986. The Hubble telescope was launched into space on April 25, 1990, and was sending pictures back to earth in a matter of days -- but the pictures were out of focus. The problem was found to be a flaw in the giant mirror -- it was too flat on one edge by 1/50th the width of a single human hair.
In 1993, the problem with the Hubble was resolved when the space shuttle Endeavor captured the Hubble Space Telescope and added a camera to correct problems with the telescope's primary mirror.
There have been other problems with the Hubble over the years, but it is still one of the wonders of the world and is providing astronomers with information that they could never have gained access to without it.
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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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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.
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