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Author Topic: Whajafink? New Planet - WASP 17  (Read 2985 times)

Offline JimBob

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Whajafink? New Planet - WASP 17
« on: 15/08/2009 02:25:47 »
Two articles on this.

FIRST, BELOW, FROM WIKIPEDIA - http://en.wikipedia.org/wiki/WASP-17
SECOND IS FROM - http://news.yahoo.com/s/space/20090812/sc_space/newfoundplanetorbitsbackward


WASP-17 is an F-type main sequence star approximately 1,000 light-years away in the constellation Scorpius.[1][2] As of 2009, an extrasolar planet has been confirmed to orbit the star. The planet is thought to orbit in a retrograde orbit (opposite the star's rotation).

Planetary system

The star is unusual in that it has an orbiting exoplanet, WASP-17b, which is believed to orbit in the opposite direction to the star's spin and is said to be twice the size of Jupiter, but half its mass.

The planet was discovered by the SuperWASP project, hence the name.



AND SECOND -

Updated 11:05 a.m. ET

Planets orbit stars in the same direction that the stars rotate. They all do. Except one.

A newfound planet orbits the wrong way, backward compared to the rotation of its host star. Its discoverers think a near-collision may have created the retrograde orbit, as it is called.

The star and its planet, WASP-17, are about 1,000 light-years away. The setup was found by the UK's Wide Area Search for Planets (WASP) project in collaboration with Geneva Observatory. The discovery was announced today but has not yet been published in a journal.

"I would have to say this is one of the strangest planets we know about," said Sara Seager, an astrophysicist at MIT who was not involved in the discovery.

What's going on

A star forms when a cloud of gas and dust collapses. Whatever movement the cloud had becomes intensified as it condenses, determining the rotational direction of the star. How planets form is less certain. They are, however, known to develop out of the leftover, typically disk-shaped mass of gas and dust that swirls around a newborn star, so whatever direction that material is moving, which is the direction of the star's rotation, becomes the direction of the planet's orbit.

WASP-17 likely had a close encounter with a larger planet, and the gravitational interaction acted like a slingshot to put WASP-17 on its odd course, the astronomers figure.

"I think it's extremely exciting. It's fascinating that we can study orbits of planets so far away," Seager told SPACE.com. "There's always theory, but there's nothing like an observation to really prove it."

Cosmic collisions are not uncommon. Earth's moon was made when our planet collided with a Mars-sized object, astronomers think. And earlier this week NASA's Spitzer Space Telescope found evidence of two planets colliding around a distant, young star. Some moons in our solar system are on retrograde orbits, perhaps at least in some cases because they were flying through space alone and then captured; that's thought to be the case with Neptune's large moon Triton.

The find was made by graduate students David Anderson at Keele University and Amaury Triaud of the Geneva Observatory.

Bloated world

WASP-17 is about half the mass of Jupiter but bloated to twice its size. "This planet is only as dense as expanded polystyrene, 70 times less dense than the planet we're standing on," said professor Coel Hellier of Keele University.

The bloated planet can be explained by a highly elliptical orbit, which brings it close to the star and then far away. Like exaggerated tides on Earth, the tidal effects on WASP-17 heat and stretch the planet, the researchers suggest.

The tides are not a daily affair, however. "Instead it's creating a huge amount of friction on the inside of the planet and generating a lot of energy, which might be making the planet big and puffy," Seager said.

WASP-17 is the 17th extrasolar planet found by the WASP project, which monitors hundreds of thousands of stars, watching for small dips in their light when a planet transits in front of them. NASA's Kepler space observatory is using the same technique to search for Earth-like worlds.


 

Offline LeeE

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Whajafink? New Planet - WASP 17
« Reply #1 on: 15/08/2009 15:40:51 »
Very curious indeed.  It's one thing to have a small moon in a retrograde orbit but changing the direction of something half the mass of Jupiter is rather a different issue.

A small retrograde orbit moon can be explained fairly easily; in a collision between two large bodies there will be a few small fragments of debris that end up traveling in the opposite direction, with the total momentum being preserved in the majority of the debris.  Half the mass of Jupiter would be one heck of a big 'small' fragment though.

I guess there's a possibility that other bodies might be found in this system, and if so, then it's possible that rather than simply having a retrograde orbit, the axis and plane of the orbit has been slowly tilted over by 180 deg by the influence of the other bodies.  I think this would need the other bodies to be orbiting out of the ecliptic plane though, so it's still pretty weird - how did the other bodies end up out of the ecliptic plane?

I look forward to hearing more about WASP-17b and its system.
 

Offline Stefanb

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Whajafink? New Planet - WASP 17
« Reply #2 on: 15/08/2009 15:52:02 »
Does the spin of a star actually affect the orbit of a planet? If so, would that mean that something in retrograde orbit would be going slower and slower as time progresses?
 

Offline Nizzle

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Whajafink? New Planet - WASP 17
« Reply #3 on: 18/08/2009 09:46:41 »
So this is the only planet in the entire universe where the sun rises in the west and sets in the east?

Now that's a touristic attraction!
 

Offline neilep

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Whajafink? New Planet - WASP 17
« Reply #4 on: 22/08/2009 11:36:14 »
So this is the only planet in the entire universe where the sun rises in the west and sets in the east?

Now that's a touristic attraction!

If ewe change the labels on every compass in the world then we can make the sun rise from any locale....yes...yes we can do this....easy peasy..I do it now !
 

Offline RD

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Whajafink? New Planet - WASP 17
« Reply #5 on: 22/08/2009 12:14:42 »
So this is the only planet in the entire universe where the sun rises in the west and sets in the east?

Now that's a touristic attraction!



There's one closer to home where that occurs ...
Quote
Venus as the planet that spins east to west. In other words, if you arrived on Venus in the morning, the sun would be in the west and would set in the east.
http://media.caltech.edu/press_releases/11764

Any tourists visiting Venus will require heavy-duty air conditioning
Quote
The temperature and pressure at the surface are 740 K (467C) and 93 bar, respectively.
http://en.wikipedia.org/wiki/Atmosphere_of_Venus
 

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Whajafink? New Planet - WASP 17
« Reply #5 on: 22/08/2009 12:14:42 »

 

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