51.   If this planet is unique, E.T. can forget it.

52.   If the planet was a gaseous giant like Jupiter, some astronomers said, the heat might have long ago driven off all its hydrogen atmosphere.

53.   If they instead formed the way stars do, they might have little relevance in estimating how common planets might be.

54.   If you think of it more in a communal sense, the planet is full.

55.   If Gray is right, then a few other reputed extrasolar planets also may be illusions.

56.   In retrospect, I see that the planet would have been healthier if we had all stayed home.

57.   In some cases, the planets could be perturbed because their star is part of a binary system, where two stars are locked in gravitational embrace.

58.   It now seemed clear that extra-solar planets are anything but a rare phenomenon.

59.   It may be that small solid planets are truly rare.

60.   It was a hokey exhibit, but everybody remembers it because it gave you at least a hint of what another planet was like.