Astronomers monitoring the Kepler space telescope have detected nearly 1,300 planets flying in orbit around distant stars, a cosmic search that began nearly 10 years ago inside a rusty old telescope dome at the Lick Observatory atop Mount Hamilton near San Jose. From the size and orbits of the new-found “exoplanets,” the astronomers said at least 550 could be rocky planets much like Earth, and at least nine are orbiting at just the right distance from their stars to lie inside their “habitable zones” where temperatures would be just right for liquid water, the one ingredient essential for life to...