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http://www.newscientistspace.com/article/dn8985-tenth-planet-as-bright-as-fresh-snow.html
Tenth planet as bright as fresh snow
21:12 11 April 2006
NewScientist.com news service
Maggie McKee
The "tenth planet" is only slightly larger than Pluto, new Hubble Space Telescope images prove. It had been thought the planet, dubbed Xena, might be 25% to 30% larger.
Intriguingly, the downsizing means the distant world must be brighter than almost any other object in the solar system, suggesting it is constantly being resurfaced.
Xena, officially called 2003 UB313, was first announced in July 2005 and lies about three times as far from the Sun as Pluto. Its brightness suggested it was larger than Pluto, but it was not clear by how much because astronomers did not know how much sunlight its surface reflected.
Xena?s discoverers, led by Mike Brown at the California Institute of Technology in Pasadena, US, first thought its surface might be similar to that of Pluto, which reflects about 60% of sunlight. If so, Xena would be 25% larger than Pluto, an estimate borne out by recent ground-based observations of its heat, which suggested it was 30% larger.
But these results had a large margin of error ? 400 kilometres. Now, Brown and colleagues have analysed Hubble images taken in December 2005 to reveal Xena\'s size to the nearest 100 kilometres. Hubble was able to resolve Xena at visible wavelengths, showing its diameter is 2400 kilometres - about 5% larger than Pluto?s 2290 kilometres.
Frozen methane
The fact that Xena is smaller than initially thought means it must reflect about 86% of the light that falls on it - making it about as bright as fresh snow and brighter than every other solar system body except Saturn\'s moon Enceladus. Spectral observations suggest its surface is covered with frozen methane, like Pluto.
But unlike Pluto, which is mottled by both bright and dark splotches, Xena is so uniformly bright that it is impossible to tell how fast it is rotating. "When we made the size measurement, we were thoroughly shocked," Brown told New Scientist. "Such a high albedo is simply unprecedented other than the very odd Enceladus."
Richard Binzel, a planetary scientist at the Massachusetts Institute of Technology in Cambridge, US, agrees. "Space is a dirty place," he says, explaining that particles from the solar wind alter the structure of ices, darkening them over time. "It\'s very hard to keep a surface bright and white - it requires some process to keep the surface fresh."
Brown suggests two possible mechanisms, working together, for the resurfacing. Xena moves in a very elongated orbit that stretches from 38 to 97 astronomical units (1 AU is the distance between the Sun and Earth). When it is near the Sun in its 560-year orbit, it may have a gaseous atmosphere. But when it moves away, it receives so little sunlight that any atmosphere would freeze onto Xena\'s surface, leaving it fresh and white.
But a similar freeze-thaw cycle occurs on Pluto, which moves from 30 to 50 AU over about 250 years, says Binzel. And it does not have a blindingly bright surface.
"So it may also be that fresh methane is leaking out of the surface," suggests Brown. Ice particles and water vapour spew from geysers on the snow-white Enceladus, but Brown says such violent jets are not necessary on Xena. "Instead it would be more like a picture of a steam vent in Antarctica, where the steam instantly freezes onto the surface," he says.
Gravitationally stretched
But he and other astronomers had thought that Xena\'s interior was made of rock and ice. For gaseous methane to survive within the planet, "you have to have an energy source", says Binzel. Brown agrees: "The real question is: Why would methane leak out of the surface?"
Some objects are heated when they are gravitationally stretched and compressed by massive objects nearby. But though Xena has a moon that might be a tenth its size, it is too small to gravitationally deform and heat Xena, says Brown.
Similarly, the decay of radioactive isotopes could not provide the necessary heat, says Binzel: "It\'s a wonderful mystery."
The Hubble observations will be published in a future issue of the Astrophysical Journal. -
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Planet Xena? You gotta be **** kidding me...Might as well call it planet Millhouse.
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Yeah I am quite disappointed with that as well.
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Informative. Here\'s a post so you don\'t hear those crickets.
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i thought this thread was gonna be about sadie.
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The team refers to the object informally by the nickname Xena, after the television series Xena: Warrior Princess. They had saved this name for the first body they found that was larger than Pluto. The X of Xena is a reference to Percival Lowell\'s Planet X; they had wanted more female names for astronomical bodies, and this was the closest they could come to a mythological female name beginning with X. On the other hand, the team has also claimed that they chose the name because "We have always wanted to name something Xena" [12], seemingly implying that the name was chosen prior to the association with Planet X. The name Xena has been used by news media such as CNN, but it has not been proposed to the IAU.
The second reported name, Lila, is not a nickname for 2003 UB313, but rather comes from "Planet Lila", the name of the discovery web page URL, which was named after Michael Brown\'s newborn daughter, Lilah.
Two days after announcing the discovery, Brown discussed his team\'s ideas about naming the objects on his website:
"If the object falls under the rules for other Kuiper belt objects, however, it must be named after some figure in a creation mythology. We have decided to attempt to follow that ruling scheme. […] One such particularly apt name would have been Persephone. In Greek mythology Persephone is the (forcibly abducted) wife of Hades (Roman Pluto) who spends six months each year underground. The mourning of her mother Demeter causes the dead of winter. The new planet is on an orbit that could be described in similar terms; half of the time in the vicinity of Pluto and half of the time much further away. Sadly, the name Persephone was used in 1895 as a name for the 399th known asteroid. The same story can be told for almost any other Greek or Roman god of any consequence […] Luckily, the world is full of mythological and spiritual traditions. In the past we have named Kuiper belt objects after native American, Inuit, and [minor] Roman gods. Our new proposed name expands to different traditions, still." [13]
He added later on his website that IAU lacks consensus on what the object is, and even which committee should be charged with approving its name. The committee which oversees major planets has suggested that if this object is classified as a major planet, the naming should continue the Greco-Roman tradition for planets. Brown indicated in a recent article [14] that he would propose the name Persephone if this tradition were to be upheld, despite the fact that this name has been assigned to the 399th known asteroid. Persephone has often been used in science fiction as the name of the tenth planet: see tenth planets in fiction.
When thinking of a name, co-discoverer Chad Trujillo went on the record as saying, "The name may turn out not to be Greek or Roman — there are so many asteroids named now that there are very few Greek/Roman names left!" Their previous record of names has been to be inclusive of other cultures, including Native American and Irish folklore.
http://en.wikipedia.org/wiki/2003_UB313#Name -
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So I guess Lucy Lawless is out of the question... Maybe they could name it after fictional mythology. (yes it sounds redundant but hear me out) why not use some of the gods in the Silmarillion? Could they use Norse gods to name a Kuiper belt object, or is that reserved for another belt? Still this is very interesting, and bright, man is that bright. I wonder if we could see it from earth if the conditions are right?
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http://www.msnbc.msn.com/id/14489259/
Scientists have taken away Pluto\'s planet status, for perspective on just how small it is scroll down in the link for it\'s contrast w/ the US. -
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Wow, I feel kinda out of touch here... but what\'s with this planet Ceres between Mars and Jupiter... that wasn\'t part of my second grade solar system diorama!
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Pluto is still a dwarf planet, just not good enough to be in our solar system. People can make facts up to prove or disprove anything.
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Quote
In the end, only about 300 astronomers cast ballots.
I say we start an online vote... there\'d be more than 300 people voting on whether or not Pluto should/shouldn\'t be a planet! :lol: -
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Horse-hockey!!!
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Quote from: SlimPickens
Wow, I feel kinda out of touch here... but what\'s with this planet Ceres between Mars and Jupiter... that wasn\'t part of my second grade solar system diorama!
I think that Ceres was the planet that is now "the asteroid belt" I can only assume it was the Death Star that caused Ceres to become an orbiting belt of asteroids..... -