118 résultats pour "astronomy"
- Meteorite - astronomy.
- Sputnik - astronomy.
- Mariner - astronomy.
- Skylab - astronomy.
- Season - astronomy.
- Mir - astronomy.
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Salyut - astronomy.
Contributed By:David S. F. PortreeMicrosoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.
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Soyuz - astronomy.
Since 1978, citizens of Czechoslovakia, France, Mongolia, Cuba, the United Kingdom, and about 20 other countries have flown on Soyuz spacecraft. In March 1995,American astronaut Norman E. Thagard flew in Soyuz-TM 21 to Mir; he returned to Earth in July 1995 on the U.S. space shuttle Atlantis. The collapse of the Soviet Union left Russia with less money and fewer resources for spaceflight programs than in the past. Nevertheless, Russia managed to keep theMir space station continuously staffed wit...
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Redshift - astronomy.
Astronomers can also use redshift to identify the oldest and most distant objects in the observable universe. Astronomers believe that quasars are the most distantobjects in the universe, because they have some of the largest redshifts. Quasars are objects in space that strongly emit radio waves. Astronomers originally namedthese objects quasars, which stands for quas i-stell ar (or starlike) radio source, because they appear as points of light, like stars, in photographs of the sky. When astro...
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Pluto - astronomy.
depended on how Pluto was classified. The status of Pluto drew world attention in 2006 when the official body that governs the naming of astronomical objects, the International Astronomical Union (IAU),voted for an official definition of the term planet . According to the standards adopted, a “classical planet” must orbit the Sun, must have a rounded shape from effects of its own gravity, and must be the dominant object in its region of space, having cleared the neighborhood of its orbit of oth...
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Saturn - astronomy.
measurements of the magnetic field made by the Voyager space probes in the 1980s. Additional Cassini findings reported in March 2007 suggested that particles originating from geysers on the moon Enceladus may provide a partial explanation for thechange. The neutral gas particles become electrically charged and are captured by Saturn’s magnetic field, forming a disk of hot, ionized gas around the planet’sequator. The charged particles interact with the magnetic field and slow down the rotation of...
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Asteroid - astronomy.
Asteroids of the S type, related to the stony iron meteorites, make up about 15 percent of the total population of asteroids that can be seen from Earth. Much rarer arethe M-type objects, corresponding in composition to the meteorites known as “irons.” These objects are made up of an iron-nickel alloy and may represent the cores ofbodies that were large enough to differentiate into layers and to melt deep inside. Their rocky outer layers may have been removed by impacts with other asteroids . A...
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Comet - astronomy.
may exceed the planet Jupiter in size, however. Observations from telescopes on Earth and in space indicate that most of the gases in the coma and tail of a comet are fragmentary molecules, or radicals, of the mostcommon elements in space: hydrogen, carbon, nitrogen, and oxygen. The radicals, for example, of CH, NH, and OH may be broken away from the stable molecules CH 4 (methane), NH 3 (ammonia), and H 2O (water), which may exist as ices or more complex, very cold compounds in the nucleus. Al...
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Moon - astronomy.
B Volcanic Features Maria, domes, rilles, and a few craters display indisputable characteristics of volcanic origin. Maria are plains of dark-colored rock that cover approximately 40 percent ofthe Moon's visible hemisphere. The maria formed when molten rock erupted onto the surface and solidified between 3.16 billion and 3.96 billion years ago. This rockresembles terrestrial basalt, a volcanic rock type widely distributed on Earth, but the rock that formed the maria has a higher iron content an...
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Light - astronomy.
Each different frequency or wavelength of visible light causes our eye to see a slightly different color. The longest wavelength we can see is deep red at about 700 nm.The shortest wavelength humans can detect is deep blue or violet at about 400 nm. Most light sources do not radiate monochromatic light. What we call white light,such as light from the Sun, is a mixture of all the colors in the visible spectrum, with some represented more strongly than others. Human eyes respond best to greenlight...
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Rocket - astronomy.
the vacuum of space, however, demonstrated that this belief was not true. In fact, rockets produce more thrust in the vacuum of space than on Earth. Air pressure andfriction with the air reduce a rocket’s thrust by about 10 percent on Earth as compared to the rocket’s performance in space. B Thrust and Efficiency Thrust is a measurement of the force of a rocket, or the amount of “push” exerted backward to move a rocket forward. Thrusts vary greatly from rocket to rocket.Engineers measure thrust...
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- Big Dipper - astronomy.
- Challenger Disaster - astronomy.
- North Star - astronomy.
- Radiation Belts - astronomy.
- Alpha Centauri - astronomy.
- Yuri Gagarin - astronomy.
- Black Hole - astronomy.
- John Glenn - astronomy.
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- Valentina Tereshkova - astronomy.
- Ranger (spacecraft) - astronomy.
- Buzz Aldrin - astronomy.
- Saturn (rocket) - astronomy.
- White Dwarf - astronomy.
- Surveyor (spacecraft) - astronomy.
- Space Station - astronomy.
- Neil Armstrong - astronomy.
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- Mercury Program - astronomy.
- Magellan (spacecraft) - astronomy.
- Viking (spacecraft) - astronomy.
- Voskhod Program - astronomy.
- Gemini Program - astronomy.
- Lunar Orbiter - astronomy.
- Supergiant (star) - astronomy.
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Vostok Program - astronomy.
At almost five days in duration, Vostok 5 remains the longest solo space mission ever. Valeri Bykovskii flew alone for 81 orbits and 3 million km (2 million mi) from June14 to June 19, 1963. Valentina Tereshkova became the first woman in space when she flew aboard Vostok 6 from June 16 to June 19, 1963. On its first orbit, Vostok 6passed within 5 km (3 mi) of Vostok 5. Tereshkova flew on for 2 days 22 hours, covering 1.9 million km (1.2 million mi) in 48 orbits. Soviet engineers planned a Vostok...
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Mars Pathfinder - astronomy.
Pathfinder and Sojourner also gathered engineering data for planning future Mars missions. Pathfinder entered Mars's atmosphere without first stopping in Mars orbit,an approach likely to be used by future landers, and its previously untried airbag system performed flawlessly. Sojourner needed about three months to traverse lessthan 90 m (less than 300 ft), but demonstrated that rovers can explore Mars. Engineers predict that the next generation of Mars rovers will be able to travel thousandsof k...
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Galileo (spacecraft) - astronomy.
Great Red Spot, sustains itself on energy gained from the upper atmosphere, perhaps by absorbing the energy of smaller atmospheric disturbances. In 1999 Galileotook detailed photographs of Io’s volcanic eruptions; scientists hope to use the observations to learn more about similar volcanic activity that occurred on Earth eonsago. Observations taken by Galileo in 2000 lent strength to the theory that Europa may have an ocean of liquid water. The spacecraft’s magnetometer recorded regularchanges i...
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Pioneer (spacecraft) - astronomy.
The Pioneer Venus spacecraft contributed a tremendous amount of new information about Venus. Venus showed an enormous difference between night (-170°C, or -274°F) and day (40°C, or 104°F) temperatures in the highest regions of the atmosphere (the thermosphere during the day and the cryosphere at night) at altitudesbetween 130 and 200 km (between 81 and 120 mi). Below the clouds was a region of constantly high temperature and pressure and almost no wind. The Pioneer Venuscraft found the clouds ar...
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Ulysses (spacecraft) - astronomy.
Ulysses was also used to study comet Hale-Bopp, which was first seen in 1995. Hale-Bopp travels an unusual path at a large angle to the ecliptic, and the trajectory ofUlysses was well suited to capture images of Hale-Bopp as it made its way around the Sun. Astronomers paid particular attention to Hale-Bopp’s plasma tail—a plume ofionized, or electrically charged, gas within the main tail that streams away from the comet when it approaches within about 1.5 AU from the Sun. They found that theplas...
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Meteor Shower - astronomy.
Meteor observations with radar work much the same way that observations with radio forward scattering observations do. With radar, the receiver and transmitter areat the same place. Both methods provide numbers of meteors per hour, without the visual observer’s dependence on a clear, dark sky. Astronomers can determine the orbit of the particle stream that creates a meteor shower by finding out the radiant of the shower and the speed of the meteors.Observers must record meteors with cameras or v...
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Aerospace Medicine - astronomy.
medically as aeroembolism and popularly as the bends, leads to confusion, paralysis, or neurocirculatory collapse. The most characteristic symptoms of the bends arepain in the large joints resulting from pressure of the gas on tendons and nerves, together with spasm of the blood vessels. Preflight inhalation of pure oxygen toeliminate nitrogen from the system has proved valuable as a preventive measure. Rapid decompression, resulting from accidental failure at high altitudes of thepressure withi...
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Mercury (planet) - astronomy.
In 1991 powerful radio telescopes on Earth revealed signs of possible deposits of ice in the polar regions of Mercury. These ice deposits occur in areas where sunlightnever falls, such as crater bottoms near both of the planet’s poles. Similar ice deposits may have been found during the 1990s near the poles of the Moon by theClementine and Lunar Prospector spacecrafts. The ice on Mercury likely comes from comets or water-bearing meteorites that have hit Mercury over the planet’s historyup throug...
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Natural Satellite - astronomy.
Titan, Saturn’s largest moon, also has few impact craters. Although icy volcanism from water and ammonia may occur along with some tectonic activity, Titan’s youngsurface is most likely the result of weather processes. Titan’s dense, cold atmosphere precipitates particles of complex organic molecules that accumulate as dunes andmountains. Methane rain erodes the surface and creates lakes at the moon’s poles. Triton’s young surface also may result from processes in its atmosphere, as well aserupt...
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Uranus (planet) - astronomy.
V COMPOSITION AND STRUCTURE A Interior of Uranus Uranus contains mostly rock and water, with hydrogen and helium (and trace amounts of methane) in its dense atmosphere. Astronomers believe that Uranus, likeNeptune, formed from the same material—principally frozen water and rock—that composes most of the planet’s moons. As the planet grew, pressures andtemperatures in the planet’s interior increased, heating the planet’s frozen water into a hot liquid. Uranus probably has a relatively small roc...
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Neptune (planet) - astronomy.
The gaseous atmosphere of Neptune contains hydrogen, helium, and about 3 percent methane. It extends about 5,000 km (about 3,000 mi) above the planet’s ocean.Light reflected from Neptune’s deep atmosphere is blue, because the atmospheric methane absorbs red and orange light but scatters blue light. In 1998 astronomersalso identified molecules of methyl in Neptune’s atmosphere. Methyl molecules each contain one carbon atom and three hydrogen atoms. Methyl molecules are knownas hydrocarbon radical...