Newfound Planet Might Be Near Death

A newly discovered planet that whips around its star in less than a day may have been found mere cosmic moments before its demise.

The planet, WASP-18b, is one of the "hot Jupiter" class of planets that are huge in size (10 times the mass of Jupiter in this case), but orbit very close to their stars. Their very existence was surprising to astronomers when the first of them were found a few years back. Now they've become common discoveries.

But this scorched, gaseous world is only one of two known exoplanetsthat orbits its star in less than one Earth day (0.94 days to be exact). Coupled with its hefty mass, this leads to strong gravitational tugs between the planet and its star, WASP-18. (WASP stands for the Wide Angle Search for Planets, run by several universities in Britain.)

These gravitational interactions create tides thought to squeeze and stretch the planet and even alter its orbit: If the planet orbits faster than the star spins, the planet should be pulled inward toward the star; if the star spins faster, the planet should be pushed outward (the latter is the case with the moon's orbit around Earth; the moon is moving away from us as you read this).

Given what astrophysicists know about the dynamics involved, astronomers think WASP-18b is moving toward its host star, but that would make observing the planet a 1-in-1,000 shot: While planets spend most of their lives sort of growing up, they perish in a cosmic blink of the eye. And so there is only a small time window where a planet would be in this position of impending demise — it would be statistically more likely to have found it much earlier in its lifetime, or after its destruction (which means it wouldn't have been seen at all).

"Either the odds of finding it are really small, and we just got lucky," or there's something fundamental about the tidal interactions between stars and their planets that astronomers are missing, said Douglas Hamilton, an astronomer at the University of Maryland in College Park who was not involved with the finding. link..