What about Sedna?

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tredicino

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I'm all for Pluto being demoted. It should not have been considered until they new more about it. My concern is that we now have 8 planets by definition but what about Sedna? It may be far but still falls under the new definition.
 
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mikeemmert

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That's a good question. The other stuff in the outer solar system is actually well-classified as cubewanos, plutinos, twotinos, and scattered disc objects. In addition, there are "cold" cubewanos (whose orbital plane is close to the planets) and "hot" cubewanos (whose orbital plane is tilted compared to the planets).<br /><br />Sedna plainly does not belong to the Kuiper belt. They don't know what it is, actually, although there are some guesses. It might actually be a refugee from another star.<br /><br />You are right that Sedna is more likely round than not and dominates it's orbital slot. But, plainly, it is not a planet. It would be a mistake to call it a planet because of a pair of technicalities. That's what happened with Ceres and Pluto.<br /><br />Sedna is in a new class. Maybe YOU can come up with a catchy new name for this class of objects! The new PAN-Starrs telescope system just opening up in Hawaii, with 1.4 billion pixels in each of four chips on four different telescopes, just might find quite a few of these things.
 
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MeteorWayne

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Do you have a list of the definitions for these classes of TNO's (including the old plutinos ).<br />It might enhance the understanding here.<br />I've tried to find one, but haven't come across a list for all anywhere. <br />I suppose because they are research tools, not definitions <img src="/images/icons/smile.gif" /><br />I'll keep looking....<br /><br />MW <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
 
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MeteorWayne

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Well here are two links. Wikpedia was pretty good, also a link here for one of the researchers.<br /><br />Wiki: link <br /><br />Quick summary:<br /><br />Plutinos are in 2:3 resonance with Neptune; i.e. Pluto orbits twice for every 3 Neptune orbits.<br /><br />Twoinos orbit once for every 2 Neptues rounds.<br /><br />The result of the resonance is that these objects tend to be stable in those orbits.<br /><br />cubewanos are objects beyond neptune that are not in a resonant orbit with it. <br />The "classical" Kuiper belt.<br /><br />Some are in low inclination orbits, less than 5 degrees. Cold<br />The rest are scattered in inclinations between 5 and 30 degrees. Hot.<br />There are other regions further out.<br /><br />Read and learn.<br />That is the great value of the current debate. Now we can look at all the new things we are discovering out there and learn.<br /><br />Pluto is but one of a lrage population of objects past Neptune (although the numerous Plutinos pass inside of Neptune's orbit). It's not unique. The rest of the planets are.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
 
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3488

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There are ideas that Sedna was captured by the sun from a passing star in the remote past (perhaps one of the sun's own siblings, within the cluster the sun formed in. or more excitingly, from a real stranger that happened to be passing by).<br /><br />If so, then New Horizons 2 should be restarted ASAP, as an encounter with an extrasolar object like this would be of immense value. <br /><br />If indeed Sedna is a capturoid, perhaps we could learn a little about the nature of its original star, its age, compostion, etc.<br /><br />Apparently Sedna is very red, one of the reddest objects known orbiting our sun (redder than Mars & asteroid 6 Hebe).<br /><br />Even if not, Sedna is still a real whacko & worthy of a close pass.<br /><br />What does mikeemmert think?<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>
 
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alokmohan

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Sedna is sedna.Nothing like i .Its not KBO AS I thought.It seems oort cloud object.Any way it is not planet in same logic as pluto is .
 
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alokmohan

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Sedna might be oort cloud object as in the enclosed news.<br /> <br />'New planet' may have a moon <br /><br />The object appears very red<br /><br /><br />Enlarge Image<br /> <br />The distant object that some astronomers think could be the Solar System's 10th planet may have a moon. <br />The new planetary candidate, which has been named Sedna, rotates more slowly on itself than expected, suggesting it may have a satellite orbiting it. <br /><br />One of the scientists who found Sedna has been giving further details of its discovery at a news conference. <br /><br />Observations show it measures less than 1,700km (about 1,000 miles) in diameter, which is smaller than Pluto. <br /><br />"We think that there's evidence there is a satellite around Sedna," said Dr Mike Brown, of the California Institute of Technology, US, and leader of the research team that found the body. <br /><br />"We're hoping in the very near future to get some observations from the Hubble Space Telescope that should put that question to rest." <br /><br />Sedna was first seen on 14 November 2003 with the 48-inch Samuel Oschin Telescope at California's Palomar Observatory. Astronomers from the California Institute of Technology, Yale University and the Gemini Observatory were involved in the discovery. <br /><br />Sedna, which is named after the Inuit goddess of the ocean, is both very shiny and very red - the reddest object in the Solar System after Mars. <br /><br />Further than Pluto <br /><br />Sedna, or 2003 VB12, as it was originally designated, is the most distant object yet found orbiting our Sun. It is currently three times further away than Pluto (average distance to the Sun is 5.9 billion km or 3.6 billion miles). <br /><br />"The Sun appears so small from that distance that you could completely block it out with the head of a pin," said Dr Brown. <br /><br /> <br />Sedna is currently about 13 billion km from Earth <br />He added that, in his view, the object's apparently small size suggested it should not be cla
 
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ultimate_skywalker

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I'd like to ask if one of the criteria for classifying planets is that "it should have cleared anything around its orbit", then how do you go about Jupiter who has trojan asteroids at its lagranian points and are along the orbit of this jovian planet?
 
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MeteorWayne

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Hi and welcome to SDC.<br /><br />This subject has been beaten to death, fried, baked, and eaten. Notice the post you replied to was from 3 months ago.<br /><br />Rather than going over it all again, I'd suggest doing a search with the word Pluto and check out the threads in Space Science and Astronomy, and Ask the Astronomer.<br /><br />There are dozens, which have discussed this very issue.<br />It's enough reading to keep you busy for a week <img src="/images/icons/smile.gif" /><br /><br />The IAU resolution (which everyone agrees is badly worded, no matter what it's intention)<br /><br />"(1) A "planet" (1) is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.<br /><br />(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape (2) , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.<br /><br />(3) All other objects (3) except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies". <br /><br />Note it doesn't say "cleared anything around it's orbit", rather it says has cleared the "neighborhood" around it's orbit.<br /><br />It's a subtle difference. That may or may not be significant. Yes, the issue of Trojans makes a mess of that definition.<br /><br />MW<br /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
 
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