End of the World–or Maybe Not

In about five billion years, current thinking goes, the Sun will use up the hydrogen that fuels it and expand into a red giant, 100 times larger in diameter than it is today.  In the process, Mercury, Venus, and possibly Earth will be consumed–burned to cinders and then swallowed by the giant, aging star that used to nurture us. So the clock is ticking.  Only five billion years to go?  I remember being really bummed out when I first heard this as a kid, not understanding that five billion years is a really, really long time. But maybe there’s hope.  In Thursday’s edition of NATURE, Roberto R. Silvotti of Italy’s Istituto Nazionale de Astrofisica reports, along with 20 colleagues, that he’s found a planet, 4,500 light-years away, orbiting a star that went through the same cataclysm–and yet the planet is still there. The star, known as V 391 Pegasi, was probably quite similar to our sun at one time, and the newly-found planet, though much larger, was almost exactly as far away from it as we are from our sun. But something happened.  For reasons the researchers say they do not understand, V 391 Pegasi lost much of its mass as a red giant.  A star with less mass exerts less gravity, so its planet drifted into a more distant orbit, about 160 million miles away (we’re 93 million miles away from our Sun).  It survived, and the researchers, who were looking at the star for other reasons, stumbled upon it. What does this mean to us earthlings?  Maybe–hardly certain, but maybe–our planet will have the same luck.  Reuters spoke to Don Kurtz of the University of Lancashire, who was on the research team.  "The future of the Earth is to die with the sun boiling up the oceans, but the hot rock will survive," he said. I feel much better now, and I hope you do too. 
(Artist’s conception of V 391 Pegasi and its planet by Mark Garlick.  Copyright HELAS.  Used by permission from NATURE.)