A greenish comet named 103P/Hartley 2 flew within 11 million miles of the Earth on Wednesday, one of the closest approaches by a comet in centuries. But hardly anyone is likely to see it until a Maryland-led NASA mission sends a spacecraft past on Nov. 4. While the comet has been visible in the northern sky for weeks, it has been a difficult target for backyard stargazers, especially in light-polluted suburban skies. "This is probably one of the best comets of the year," said Armen Caroglanian, a member of an employees' astronomy club at the NASA Goddard Space Flight Center....