Word: orbiters
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...three realized that the sun's counterpart, if it existed, would have to be like no other companion star ever identified; it would travel in an enormous elliptical orbit three light-years across that would periodically take it farther from the sun than the distance between any known binary stars. Because it has not been identified in the four centuries since astronomers began using telescopes, it must be very small and dim, perhaps a red dwarf with one-third the mass and only one one-thousandth the brilliance of the sun. When it passed through the Oort cloud, it would...
Reviews for the Nemesis debut were what might be called mixed. Critics charged that so gigantic an orbit had never been recorded for two companion stars, and with good reason. If the sun and its presumed partner were actually three light-years (18 trillion miles) apart, they said, the gravitational attraction between them would be so feeble that a passing star or dust cloud would have bumped Nemesis out of orbit long ago, certainly before it could come back through the Oort cloud a dozen times. Says Shoemaker, who has been something of an impartial judge in the periodicity controversy...
...asteroids can wreak considerable havoc if they collide with the earth, they are of very different natures and origins. Asteroids are rocky chunks that range in size from pebbles to a mammoth named Ceres that astronomers estimate to be as much as 600 miles across. Most of them orbit the sun in a belt between Mars and Jupiter and are thought to be either remnants of a planet that disintegrated early in the life of the solar system or celestial building blocks that never quite coalesced into a planet. Occasionally an asteroid is slowed in its travels, probably...
...tenth planet is somewhere out there. Astronomer Robert Harrington of the U.S. Naval Observatory has gone so far as to paint a description of the suspect, and it is no pedestrian planet. It is three to five times the mass of the earth, is gaseous like Jupiter, has an orbit that is elliptical rather than circular and inclines to the plane of the solar system at an angle of perhaps 30 degrees or more; its year (the time it takes to orbit the sun once) is 800 to 1,000 earth years long. To have been influential in shaping...
...devising their Planet X model, Whitmire and fellow Louisiana Astrophysicist John Matese took an entirely different tack, determining the nature and orbit of a planet that would loose rains of comets at the necessary intervals. The result of their calculations: a planet with an orbital plane that slowly rotates around the sun, completing its cycle once every 56 million years. Twice during that cycle, every 28 million years, Planet X's orbit carries it through a disk of comets lying just beyond Neptune, dislodging many of them...