"They are not unusual," 744U-21 observed. "Most every star, some time or other, goes through this phase. We see them often from afar, but they happen so quickly and without any warning that this is a rare coincidence that we should enter a system and find conditions preparatory to a nova. This meteoric mass will surely cause one when it strikes the sun." "But I have understood that novas are not always caused by large bodies or meteor swarms colliding with a star," said the professor. "Popular theory supports a belief that often an internal solar disruption causes a star to explode. "Such a cause as you mention generally promotes a greater disturbance, especially if it originates deep within the solar body. Contact with a meteoric swarm, as this case promises to be, rarely affects little more than the surface gases of a sun." "Even so," observed 6W-438, "the cataclysm will be large enough to wipe out life on every world of this system and change the planetary surfaces. "A terrific wave of heat will spread outward from the sun with the speed of the light which carries it. For the nearer planets, it will mean but a matter of a few minutes. Possibly a day or so later, tremendous waves of gases will sweep in the wake of the blinding, searing heat. They will be sufficiently tangible to slow the speed of the planets perceptibly upon their orbits. Terrific planetary disruptions will follow in the form of earthquakes and volcanic eruptions, and entire oceans will turn to steam and bury each world in a dense cloud blanket. Temporarily, the nova will outshine every star in its neighborhood and will loom visible countless light years distant. "It will mean doomsday for all life in this system even though the sun returns once more to its normal condition within the next ten or twenty years." "It will be well to check our figures," cautioned 6W-438. "We must plan not to be such close observers that the nova will reach us." At the rate the meteoric mass was traveling sunward, Professor Jameson, as was his usual habit, figured that nearly twenty-three of his earthly days must elapse before the swarm of cosmic debris reached the sun. Their first step was to examine all the planets and find what, if any, life they supported. They had already passed a few of the outer worlds and had found them apparently lifeless. The spaceship now approached another world, a planet so large that their proximity detectors remained oblivious to all else even while they were still far off. "It is one of the larger worlds which we must avoid," Professor Jameson stated. "The gravity there is so strong we could move around only with difficulty and a superexpenditure of energy, and even if we landed safely, our spaceship would find it hard to leave." "We shall make our observations entirely by telescope, then," answered 6W-438.