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Uranus: strange encounter looming.


Uranus: Strange Encounter Looming

On the surface, as an omen of things to come, it looks pretty dull. In less than 11 weeks, the Voyager 2 spacecraft will flash past Uranus, taking the first close-ups of a planet so distant that it is virtually invisible to the naked eye. Yet photos and other data from the rapidly approaching probe still reveal only a featureless fluffball, with no radio emissions (Jupiter's can be "heard' all the way to earth) and not even a trace of the planet's bizarre rings, which were discovered from earth eight years ago when they blocked the light of a star.

But the encounter will be anything but dull. And at last week's annual meeting of the American Astronomical Society's Division for Planetary Sciences The Division for Planetary Sciences (DPS) is a division within the American Astronomical Society devoted to solar system research.[1] It was founded in 1968. The first organizing committee members were: Edward Anders, L. Branscomb, J. W. Chamberlain, R. Goody, J. S.  in Baltimore, strange Uranus was looking more mysterious than ever.

"Let me give you a sense of our rising level of panic,' quipped Michael Kaiser of the NASA NASA: see National Aeronautics and Space Administration.
NASA
 in full National Aeronautics and Space Administration

Independent U.S.
 Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately 6.5 miles northeast of Washington, D.C.  in Greenbelt, Md., as he reported that Voyager 2 was still detecting "absolutely no sign' of radio emissions from the planet. Such signals would indicate that Uranus has a magnetic field. And perhpas it has none--except that the brilliant ultraviolet glow that a group of scientists has been monitoring for four years with the earthorbiting International Ultraviolet Explorer International Ultraviolet Explorer: see ultraviolet astronomy.  satellite would suggest otherwise. The glow, from the Lyman alpha emissions of molecular hydrogen, "is interpreted as an auroral emission from an active magnetosphere,' according to John T. Clarke of the NASA Marshall Space Flight Center The George C. Marshall Space Flight Center (MSFC), the original home of NASA, is a lead center for propulsion, Space Shuttle propulsion, Shuttle external fuel tank, crew training and payloads, International Space Station (ISS) design and construction, for computers, networks, and  in Huntsville, Ala., and his colleagues. In fact, the group notes, "this magnetosphere may be comparable in strength to those of Jupiter and Saturn.'

Such a magnetosphere, however, ought to be producing the radio signals that Voyager 2 has so far failed to find. Stephen A. Curtis of NASA Goddard suggests that they could be present but radiating only from the planet's nightside Nightside may refer to:
  • The Canadian late-night radio talk show The Nightside, hosted by Mark Elliot
  • NBC's now-defunct late night news program, comparable to ABC World News Now.
. On the other hand, according to Curtis and Goddard colleague Norman F. Ness, the lack of a magnetic field (though that would still leave the presumed aurora unexplained) could bear on another, very different problem: the planet's extremely dark rings. One thing a planetary magnetic field does is help keep out the solar wind; without such a field, the researchers note, the solar wind may be constantly eroding away the ices on the particles making up the rings, leaving the particles much less bright than those in the icy rings of Saturn The rings of Saturn are a system of planetary rings around the planet Saturn. They consist of countless small particles, ranging in size from microns to meters, each on its own individual orbit about Saturn. .

Even so, the rings are so far completely absent to Voyager 2's cameras, leaving one of the encounter's major spectaculars yet to come. The earth-based measurements of occulted (blocked) starlight have suggested that there are nine principal rings. James L. Elliott of Massachusetts Institute of Technology Massachusetts Institute of Technology, at Cambridge; coeducational; chartered 1861, opened 1865 in Boston, moved 1916. It has long been recognized as an outstanding technological institute and its Sloan School of Management has notable programs in business,  and his colleagues report that two of the nine may be "double' rings, consisting of inner and outer components. Of course, the actual number may well be in the hundreds or thousands, given the myriad "ringlets' discovered by the Voyager spacecraft at Saturn. The Uranian rings, in fact, may well be more complex still. Some appear circular, others elliptical el·lip·tic   or el·lip·ti·cal
adj.
1. Of, relating to, or having the shape of an ellipse.

2. Containing or characterized by ellipsis.

3.
a.
 (or eccentric), all of them sharp-edged and narrow, and it has been suggested that many of them may be held in place by tiny satellites orbiting just inside and outside each ring.

One of the most unusual Uranus findings presented at the meeting was an infrared spectrum of the planet, reported by Glenn S. Orton of Jet Propulsion Laboratory “JPL” redirects here. For other uses, see JPL (disambiguation).

Jet Propulsion Laboratory (JPL) is a NASA research center located in the cities of Pasadena and La Cañada Flintridge, near Los Angeles, California, USA.
 in Pasadena--and he was anything but relaxed about the seeming implication of his result. "If you get the feeling I'm trying to make you feel as uncomfortable as I do,' he said as he introduced his brief talk, "you're right.'

After having gone over and over the spectrum itself, looking also for possible instrumental errors in the observations, Orton found himself confronted with the possibility that the atmosphere of Uranus The atmosphere of Uranus, like that of Neptune, is markedly different from those of the larger gas giants, Jupiter and Saturn. While still composed primarily of hydrogen and helium, it possesses a higher proportion of volatiles (dubbed "ices") such as water, ammonia and methane.  may contain about 40 percent helium--5 to 7 times as much as Jupiter or Saturn. The solar system's four big, gassy gas·sy  
adj. gas·si·er, gas·si·est
1. Containing or full of gas.

2. Resembling gas.

3. Slang Bombastic; boastful.
 planets (Neptune is the fourth) have been assumed to have at least similar ratios of helium to hydrogen, and 40 percent helium would require some explaining. It would seem to imply, for example, that the mass of Uranus is distributed more in the atmosphere and less toward its core. It could also radically affect models of how heat is produced in the planet's interior, and could throw off estimates of the planet's upper-atmospheric temperature based on stellar-occultation observations. There may be other explanations, says Orton, but "helium is the simplest thing which explains the shape of the spectrum.'

Voyager 2 is on the way.
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Author:Eberhart, J.
Publication:Science News
Date:Nov 9, 1985
Words:767
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