What Will Happen to the Planets as the Sun Dies? Q. As our Sun dies, what will happen to the planets, especially our own? A. In about five billion years, scientists estimate, the Earth will be engulfed and burned up in the expanding radius of the Sun as it evolves. This event will be about a million years after Venus and Mercury "have suffered the same fate," according to updated calculations published in 2008 in the journal Monthly Notices of the Royal Astronomical Society. It will also be long after the Earth becomes too hot to support life. As the Sun ages into a red giant, it will expand, losing mass and cooling somewhat, but remaining very hot. "While solar-mass loss alone would allow the orbital radius of planet Earth to grow sufficiently to avoid this "doomsday" scenario," the authors of the study conclude, the tidal interaction of the Sun and the closely orbiting planet "will lead to a fatal decrease" in the size of Earth's orbit. At least some of the outer planets may survive, scientists suggest. Some have conjectured that it could be possible to engineer a way to expand Earth's orbit by the small percentage needed to escape. It would involve arranging "a suitable encounter of the Earth every 6,000 years or so with a body of large asteroidal mass," perhaps objects in the Kuiper Belt. But the authors of the study note that "there is no immediate hurry to implement the scheme." Readers may submit questions by mail to Question, Science Times, The New York Times, 620 Eighth Avenue, New York, N.Y. 10018, or by e-mail to question@nytimes.com.