....Shrouded from the sun's light, mysteriously tugging at the orbits of Uranus and Neptune, is an unseen force that astronomers suspect may be Planet X-a 10th resident of the Earth's celesial neighborhood.
.... Last year, the infrared astronomical satellite (IRAS), circling in a polar orbit 560 miles from Earth, detected heat from an object about 50 billion miles away that is now the subject of intense speculation.

...."All I can say is that we don't know what it is yet," says Gerry Neugebauer, director of the Palomar Observatory for the California Institute of Technology. Scientists are hopeful that the one-way journeys of the Pioneer 10 and 11 space probes may help to locate the nameless body.
.... Some astronomers say the heat-emitting object is an unseen collapsed star or possibly a "brown dwarf"-a protostar that never got hot enough to become a star.

....However, a growing number of astronomers insist thst the object is a dark, gaseoous mass that is slowly evolving into a planet.
.... For decades, astronomers have noted that the orbits of two huge, distant planets-Neptune and Uranus-deviate slightly from what they should be according to the laws of physics. Gravitational pull from Planet X would explain that deviation.
.... Moreover, says Neugebauer, "if we can show that our own solar system is still creating planets, we'll know that it's happening around other stars,