SEARCHING FOR OTHER WORLDS

IT'S HARD TO IMAGINE TWO more undesirable pieces of extraterrestrial real estate. The first, a planet orbiting a star known as 47 Ursae Majoris, 200 trillion miles from Earth in the Big Dipper, is about twice the size of Jupiter. Like our own largest planet, it probably consists mostly of such noxious gases as hydrogen sulfide, ammonia and methane. Fierce jet streams blow unceasingly at hundreds of miles per hour, sometimes spiraling into mammoth hurricanes that last for centuries and are big enough to swallow the Earth. And if this harsh world has any solid surface at all, it's buried under...