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Distant Sedna Raises Possibility of Another Earth-Sized Planet in Our Solar System
Space.com ^ | 3/16/04 | Robert Roy Britt

Posted on 03/18/2004 2:00:00 PM PST by LibWhacker

Our corner of the galaxy got a little stranger this week with the discovery of Sedna, the most distant object ever spotted in the solar system. Now astronomers are puzzling over how it got there.

The most intriguing idea is that there might be another world as big as Earth, a gravitational bully lurking in some unexplored corner of the solar system.

Here's the problem: Scientists can't figure out how Sedna, which is about three-fourths as big as Pluto, came to have such a strange orbit around the Sun. Sedna's path is highly elliptic. It ranges from 76 astronomical units (AU) when it is closest to the Sun to 1,000 AU when it is farthest. One AU is the distance from Earth to the Sun.

"How on Earth could anything get into an orbit like that," wonders astronomer Brian Marsden. He suggests another sort of Earth might have had something to do with putting Sedna on its current, odd course.

Snowball Earth Twin?

Michael Brown, the astronomer at California Institute of Technology who led the discovery of Sedna, said the most likely scenario involves the Sun having been born in a star cluster, and several stars that were then closer to the solar system -- still more than 10,000 AU away -- were responsible for ejecting objects like Sedna.

Several astronomers not involved in the discovery support the idea that Sedna was lured outward by a star. But others don't buy that explanation.

"I don't really like that," said Marsden, who heads the Minor Planet Center in Cambridge, Mass., where newfound solar system bodies are catalogued.

Marsden favors an object closer in, a "planetary object," he told SPACE.com , perhaps at between 400 and 1,000 AU.

"Perhaps there's more than one planet out there," Marsden said. "Who knows? But let's suppose it is something of an Earth mass, maybe even a few Earth masses. A close approach could throw this object [Sedna] from something more circular into something more eccentric."

Marsden says such a scenario leaves open the question of how an Earth-sized planet could have formed so far from the Sun, where raw material should have been sparse, according to current theory.

Brown said an Earth-sized planet is indeed a possibility. But his team's calculations put it at about 70 AU.

"We think it's unlikely, because we think we would have found it by now," Brown said in a telephone interview.

Alan Boss, a planet-formation theorist at the Carnegie Institute in Washington, DC, agrees that a passing star or dense cloud of gas is the more likely cause for Sedna's strange travels. Boss said it would be "hard to imagine" forming an Earth-sized object out where the interaction would have taken place.

Region to explore

But Brown said there is one unexplored region of space left, amounting to about 20 percent of the sky, that hasn't been searched for an Earth-sized object that would be orbiting at 70 AU and presumably in the main plane of the solar system. It is the region toward the bright galactic center, which is harder to search.

Brown said his team is considering making that search now.

If Marsden's idea is on track, and there is an Earth-sized planet several hundred AU away, it would easily have escaped detection by current surveys.

Either way, this wouldn't involve any ordinary Earth. Any object beyond Pluto would be frozen solid and would not be a strong candidate for bearing life.

In a sideline argument, astronomers have differing opinions on whether Sedna should be considered a planet. Many argue that Pluto should never have been called a planet, because it is more like Sedna and other objects beyond Neptune -- small and with offbeat orbits.

In fact, however, there is no astronomical definition for the term "planet." But the International Astronomical Union has made it clear in recent years that Pluto, despite how most astronomers now view it, will not be stripped of its planethood. It is not known what astronomers would call an Earth-sized object found beyond Neptune in a circular orbit, but it would be hard not to consider it a planet.

Earths even farther out?

Alan Stern of the Southwest Research Institute adds another twist to the whole puzzle. Stern thinks there could be Earth-sized planets in the Oort Cloud, the most distant region of the solar system.

Brown's team said they thought Sedna should be counted as the first known object of the otherwise theoretical Oort Cloud. The distant reservoir of small icy objects is thought to exist based on the orbits of some comets that zoom through the inner solar system now and then, and then disappear into deep space.

Nobody knows what's actually in the Oort Cloud, however.

"I would say that is likely" Stern said in regards to possible Earth-sized planets in the Oort Cloud. In the early years of the solar system, he explained, objects as massive as Earth are thought to have hit Uranus and Neptune. Computer simulations show most of the hypothetical Earth-mass objects "would be ejected from the outer planets region, not accumulated in Uranus and Neptune, so we could someday find these frozen relics in the Oort Cloud."

Ferreting out worlds that far away would be a monumental challenge. The Oort Cloud is said to stretch nearly halfway to the next known star.


TOPICS: News/Current Events
KEYWORDS: earth; planet; planetx; sedna; xplanets
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To: LibWhacker
bump
21 posted on 03/18/2004 2:43:45 PM PST by Centurion2000 (Resolve to perform what you must; perform without fail that what you resolve.)
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To: LibWhacker
bump
22 posted on 03/18/2004 2:43:45 PM PST by Centurion2000 (Resolve to perform what you must; perform without fail that what you resolve.)
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To: RightWhale
Heck, I'd go for the chocolate alone. Anything to get a chocolate bar with more than 77% cacao, which is the best I can find on the internet. :-)
23 posted on 03/18/2004 2:44:26 PM PST by LibWhacker
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To: cripplecreek
My dragon wing is ready and we have large quantities of firestone.

M'ke
24 posted on 03/18/2004 2:49:12 PM PST by SwampFoxOfVa
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To: cripplecreek
I've known people who pass dense clouds of gas that make me want to be 1000 astronomical units away from them.
25 posted on 03/18/2004 3:39:33 PM PST by xrp
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To: LibWhacker

Answer to current Millionaire question bump.


26 posted on 05/17/2004 7:18:10 PM PDT by WinOne4TheGipper (Screw Atkins, let's go on a high CARB diet: Keep Cheney, Ashcroft, Rummy and Bush!)
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To: annie laurie; garbageseeker; Knitting A Conundrum
2004 topic, so reply at your own risk. ;') The July issue of "Astronomy Now" (a British mag, which is six months behind on its website) discusses the Nemesis theory in a breezy two page article (plus a couple pages of illustrations if memory serves), and Mike Brown doubts that Nemesis exists, but also entertains the possibility of some large body (such as the one discussed here) having been the agent for putting Sedna where it is. Brown's idea is, if more than one body like Sedna is found, orbit-wise, then it makes Nemesis more likely.

27 posted on 08/07/2006 9:50:42 PM PDT by SunkenCiv (updated my FR profile on Thursday, July 27, 2006. https://secure.freerepublic.com/donate/)
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To: SwampFoxOfVa; cripplecreek

And the queens' wing is standing by with flamethrowers ;-)


28 posted on 08/08/2006 7:02:07 AM PDT by annie laurie (All that is gold does not glitter, not all those who wander are lost)
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To: SunkenCiv

Wow, SC ... you need to put a "seizure warning" on that thing ;-)

http://upload.wikimedia.org/wikipedia/en/d/d9/Battling_seizure_Robots.jpg


29 posted on 08/08/2006 7:03:38 AM PDT by annie laurie (All that is gold does not glitter, not all those who wander are lost)
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To: SwampFoxOfVa; cripplecreek

HA! This is what I get for replying to stuff early in the morning ... I kinda missed the fact that this was a "resurrected" thread from 2004 ;-)

Sorry for any confusion :)


30 posted on 08/08/2006 7:05:40 AM PDT by annie laurie (All that is gold does not glitter, not all those who wander are lost)
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To: LibWhacker
Michael Brown, the astronomer at California Institute of Technology who led the discovery of Sedna, said the most likely scenario involves the Sun having been born in a star cluster, and several stars that were then closer to the solar system -- still more than 10,000 AU away -- were responsible for ejecting objects like Sedna.

Hey, now, unless it involves Xenu, nobody wants to be hearing yer crazy crackpot theories, mmm kay!
31 posted on 08/08/2006 7:08:04 AM PDT by BaBaStooey (I heart Emma Caulfield.)
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X-Planets
· join · view topics · view or post blog · bookmark · post new topic · subscribe ·
Google news searches: exoplanet · exosolar · extrasolar ·

32 posted on 09/01/2012 3:33:20 PM PDT by SunkenCiv (https://secure.freerepublic.com/donate/)
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