Don Kurtz: ‘Will Earth survive an expanding sun?’

Forty-five hundred light-years away, at the star V 391 Pegasi, astronomers have glimpsed a star system that might reveal a possible future for our planet Earth. They’ve identified the first planet ever to have survived the red-giant stage of its parent star. Red giants are stars that expand and begin to engulf any orbiting worlds.

Don Kurtz: It’s the first look at the very late stages of the solar system, and gets us some idea the Earth may survive the red giant stage at least as a hot rock.

That’s Donald Kurtz with the University of Central Lancashire in the United Kingdom. Kurtz told Earth & Sky that as this distant star became a red giant, its radius apparently expanded by more than a hundred times, vaporizing anything in its path. But as the star expanded, Kurtz said, it also lost mass, mostly hydrogen in its outer layers. Less mass means weaker gravity. The star loosened its grip on at least one of its orbiting worlds – enough, Kurtz thinks, for the planet to have moved outward in its orbit, safely out of range.

Don Kurtz: What we are talking about here is the difference between the Earth being completely vaporized and disappearing or very hot rock surviving until the star collapses.

This same scenario could play out in our solar system, when our sun becomes a red giant. The sun should become a red giant in about 5 billion years. This discovery could mean that – when our sun becomes a red giant – even though the oceans of Earth might boil away – a hot rock, our Earth, might yet survive.

Our thanks to:
“Donald Kurtz”:
Department of Physics, Astronomy & Mathematics
University of Central Lancashire, UK

December 18, 2007

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