(9 of 10)
Offers of assistance have come from other quarters as well. Jordin Kare, a physicist with Lawrence Berkeley Laboratory, has suggested that a 24-in. Schmidt telescope in Australia be used with a computer scanning system called the Star Cruncher to survey the Southern Hemisphere skies. If these approaches turn up a blank, Kare and Muller will launch a Star Cruncher search in the north. And at JPL, Astrophysicist Thomas Chester, chief of the I.R.A.S. data team, is sifting through recorded I.R.A.S. transmissions looking for Nemesis and other unusual objects. Although I.R.A.S. operated for only ten months in 1983 before dying, it managed to chug out data on 250,000 cosmic objects, which scientists have just begun to analyze. Chester is hunting for cool stars that may have suspiciously shifted. To date he has identified 5,000 likely objects and narrowed the list to 15, which he plans to photograph half a year apart to check further if they are candidates for the star role of Nemesis. Says Muller: "I figure all these searches could take about two years."
Early this year, another scientist joined the Nemesis hunting party. Armand Delsemme, a Belgian-born astrophysicist at the University of Toledo in Ohio, announced that he had just about zeroed in on the best place for Muller or Chester to look for the death star. He has plotted the paths of 126 comets and discovered to his great surprise that they journey around the sun in oddly skewed orbits. Some very powerful object must be out there gravitationally directing the flow of traffic, he says, and that object could be Nemesis.
Although Louisiana Astrophysicist Whitmire does not dismiss the death star theory, he thinks that his Planet X theory of periodic comet showers has greater potential. For one thing, a still undiscovered planet has a distinct advantage over Nemesis as a promising candidate because astronomers have been predicting its existence since the late 19th century, first as the ninth planet and then as the tenth. Reason: its existence and gravitational pull might explain discrepancies in the movements of Neptune and Uranus. Even the discovery of Pluto in 1930 did not fulfill the gravitational force needed to justify Uranus' meanderings, and some astronomers have long thought that a 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 the current orbit of Uranus, he thinks, it made its closest approach to that planet in the 1700s.
In 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.