U.S. scientists continue to debate over Sedna

20.09.2004

20.09.2004


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This story is reminiscent of the famous question about a cat in a dark room where there is none. In the role of the cat in this case — a hypothetical satellite of Sedna, "tenth planet" solar system, as it is called open at the end of last year, the planetoid 2003 VB12.

In fact, astronomers have not yet agreed on how to qualify the cosmic body, discovered beyond Pluto: most inclined to consider it an asteroid, someone called small planet, but it is possible that Sedna did approve the rank of "full-fledged" planet. The size of it — with three-quarters of the diameter of Pluto, and the circle around the sun makes for about 12,260 years. Sedna is moving at such an elongated orbit that is closest to the Sun, the point is removed at 74 astronomical units, and the farthest — 900. Compare: Pluto is separated from our star at 39 AU, Neptune — 30, and the Earth — one (taken as a unit times the distance between our planet and the Sun.)

But the peculiarity of Sedna, not only in its remoteness. In the end, the existence of space objects on the far outskirts of the solar system predicted astronomer Gerald Kuiper in the middle of the last century, and this hypothesis was fully confirmed in the early 1990s, when they were first discovered asteroids beyond Pluto. But Sedna struck astronomers also for its extremely slow pace: it turns on its axis in about 20 Earth days, so long a "day" is not in any of the detected cosmic bodies: if the Earth turns around in 24 hours, Jupiter and Saturn, and the lack of ten hours and many asteroids — even less. Why is it so slow Sedna?

The most logical explanation — the influence of another celestial body, inhibiting rotation of Sedna. Hence the hypothesis of the existence of a large satellite, whose gravitational pull slows the rhythm of the planetoid. A team of scientists led by Michael Brown of the California Institute of Technology in Pasadena (USA), which has the honor of opening of Sedna, has carefully studied the images taken with the telescope Hubble, and did not find any satellite of the "tenth planet". But here's the English astronomers otherwise. In the August issue of The Observatory published an article by Professor Chandra Vikramansinha from Cardiff University (UK), a summary of which is posted on its website Nature. Chandra Vikramansinh believes that the moon around Sedna's still there, but unusual, with this type of cosmic bodies Earthlings have not yet had to deal.

Satellite is not visible, says the professor, because it does not reflect light, it is an object completely black, like a comet, where the ice melted and left alone gummy carbon. The strange body of researchers figuratively called "frozen smoke", it consists of a mostly hollow, perforated resinous structure that makes up the object, absorbs more than 99 percent of the light falling on it. The estimated size of the moon Sedna reminds Pluto Charon (its diameter is around 1,170 kilometers), but to see it through optical telescopes can not be required for this technique with infrared radiation.

Perhaps, the argument about the "tenth planet" and its possible companion can be resolved with the help of NASA, involving the launch of a space probe in 2006, which should come close to the orbit of Pluto. This will provide a more detailed picture of the bodies in the so-called Kuiper belt — space on the edge of the solar system, where the lives and Sedna, with its mysterious moon.

Battery News, 17.09.2004 10:19
Source: Moskovskaya Pravda

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