Giant Planet Orbits Backwards

Astronomers with the Wide Area Search for Planets have discovered a planet, dubbed WASP-17, that is twice the size of Jupiter. That makes it the largest planet ever discovered. Unlike any other planet discovered so far, it orbits opposite to its star's direction of rotation. Astronomer David Anderson from Keele University:

"Newly formed solar systems can be violent places. Our own Moon is thought to have been created when a Mars-sized planet collided with the recently formed Earth and threw up a cloud of debris. A near collision during the early, violent stage of this planetary system could well have caused a gravitational slingshot, flinging WASP-17 into its backwards orbit."

But why is WASP-17 so big? The discovery team suggests that have been subjected to intense tides as it travelled in its strange and highly-elliptical orbit, causing it to become stretched and bloated.


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@katerina v

it wouldn't matter.. it would take at least a few thousand years unless it travels at the speed of light which is...impossible :)
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where is this planet going? and how fast? is it comming our way? and if it is, than how long do we have before it can affect our planet? nobody is talking about that. does anybody know outhere?
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@ Danny Day: Since WASP-17 is in another solar system, it's over 4.5 light-years away from us and has absolutely no effect on Earth.

If you're wondering what would happen to Earth if we started orbiting in reverse... Look at the first paragraph of my very long response to ETA's questions for my answer. In addition, since it would take something very cataclysmic to change our orbit, we wouldn't be around to enjoy our backward ride. The stronger tidal forces would probably slow Earth's rotation, making the days longer. WASP-17's orbit is also much more elliptical than Earth's; if our orbit became that elliptical, we'd probably be subjected to lethal temperature extremes. On the other hand, as long as Earth's rotation continued as it is, anyone who managed to survive would notice that the sun still rose in the east & set in the west, but the constellations would appear in reverse order. The apparent movement of planets in our solar system would change, too, as their positions in our sky partly depend on our position around the sun.
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@ ETA: Orbiting backwards might subject it to very high tidal forces, but I must confess that I don't know enough about the mechanics of these things to do more than speculate on that point. Its orbit is highly elliptical, too, which I'm sure would cause temperature extremes and would stretch it out of shape.

Of course it would have a gravitational field - all objects do. In the case of WASP-17, it would probably be twice as powerful as Jupiter's, which is many times stronger than Earth's. Assuming it had a surface you could land on, you'd not be able to stand up, or even breathe. And we don't have any rockets powerful enough to get you off the planet. So if you're planning to visit it, stay a safe distance!

As for life-forms, it's anyone's guess. For a very long time I believed that the "water is a requirement for life" statement was rather short-sighted and based on the fact that this is true for organisms on Earth (That is, if Jupiter had life, it would breathe gaseous ammonia, etc.) However, a few years ago a chemist explained hydrocarbons to me. I don't remember the details, but the upshot of it was that hydrogen is the only element that bonds readily with almost anything, is the most abundant element in the universe, and when it bonds with carbon it forms a solid "platform" for more complex chemical combinations, such as proteins, etc. An ammonia atmosphere would not yield enough chemical variety to result in something as complex as organic life. Therefore, while I'm not saying that WASP-17 has no life, I think the odds against it are pretty steep.

WASP-17 appears to be a gas giant --- a very thick envelope of gases surrounding a hot core that might be liquid or solid. This core might be twice the size of Earth --- very tiny in relation to the gas envelope. It may also, like Jupiter and Saturn, generate powerful radiation belts that would be quite lethal to any human visitors who came near it. I'm not sure we have adequate protection to make a "2001: A Space Odyssey" trip to Jupiter or Saturn feasible yet.
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