Bigger than Pluto, possible 10th planet found
{{date|July 30, 2005}}
The definition of what is and what is not a planet is being challenged by a newly announced discovery Friday. Astronomers from the [[w:Palomar Observatory|Palomar Observatory]] near [[w:San Diego, California|San Diego, California]] said they found a chunk of ice and rock in the solar system larger than [[w:Pluto (planet)|Pluto]].

The object, given the temporary generic name of [[w:2003 UB313|2003 UB<sub>313</sub>]], is about 9 billion miles away from the sun. It was first photographed in 2003 using the [[w:Gemini Observatory|Gemini Observatory]] in [[w:Hawaii|Hawaii]]. But it was an indistinguishable bright spot among a field of stars in an area of the sky where astronomers don't usually look at for planets or planet-type objects.

Solar system bodies found beyond the orbit of [[w:Neptune (planet)|Neptune]] are called "[[w:trans-Neptunian object|trans-Neptunian objects]]". One of them, [[w:Pluto (planet)|Pluto]], is also classified as a planet. Up until now all other planet-like discoveries beyond Neptune, including [[w:Sedna (planet)|Sedna]], found by the same Palomar team in 2004, are called [[w:Kuiper Belt object|Kuiper Belt object]]s, or minor planets.

===Size matters===
Using a photo taken on January 8, the Palomar team compared it with previous 2003 UB<sub>313</sub> photos to triangulate the object's distance, brightness and orbit.

Using mathematical formulas, they found a range of sizes for 2003 UB<sub>313</sub>, with an estimated average showing the approximate diameter of the new body to be about 2,600 kilometers. But even at the smallest estimate scientists are certain 2003 UB<sub>313</sub> is larger than Pluto's 2,250 kilometer diameter.

To determine size, Scientists deduce the relative size of a solar system object by its brightness, just as one can infer the size of a faraway light bulb if one knows its wattage. The reflectance of 2003 UB<sub>313</sub> is not yet known for sure. Scientists can not yet tell how much light from the sun is reflected away from its surface, but the amount of light the planet does reflect puts a lower limit on its size.

"Even if it reflected 100 percent of the light reaching it, it would still be as big as Pluto," Michael E. Brown, a professor of planetary astronomy at the California Institute of Technology said in a NASA press release. "I'd say it's probably one and a half times the size of Pluto, but we're not sure yet of the final size."

"We are 100 percent confident that this is the first object bigger than Pluto ever found in the outer solar system," Brown added.

===Why wasn't it discovered earlier?===

The object is inclined by a whopping 45 degrees to the main plane of the solar system, where most of the other planets orbit. That's why it eluded discovery: nobody was looking there until now, Brown said.

Most objects in the solar system are just a few degrees from the main plane of the solar system, called the [[w:Ecliptic|Ecliptic]].  Pluto, which is considered substantially different from the rest of the planets, is only 17 degrees from this main plane.  Astronomers who study the sky for asteroids and comets usually look in the region of the sky that the rest of the planets occupy.

The brightness of this object is just barely fainter than the telescopes from earlier sky surveys were able to identify, so new advances in the making of telescopes has also played a part in this discovery.

===The name===

Now that the discovery data has been released, the scientists will turn over their work to the [[w:International Astronomical Union|International Astronomical Union]] (IAU), which will review it, classify the object and approve a new name to replace the temporary 2003 UB<sub>313</sub>. 

Sometimes the discoverers of a new planetary body get to choose its name, but not always. "We have a name we really like, and we want it to stick," Brown told reporters at a press conference. He said the team has submitted the name to the IAU but would not disclose their choice. In the 2004 naming of Sedna, Brown noted objects found in the Kuiper Belt are usually named after deities of the Underworld. 

The astronomers have been using a code name of sorts for the discovery. The tongue-in-cheek nickname  is "[[w:Xena|Xena]]" after the fictional main character of the television series of the same name. "Because we always wanted to name something Xena," Dr. Brown said in a ''New York Times'' report.

===Defining 'planet'===
[[Image:2003 UB313 opname.jpg|thumb|450px|These time-lapse images of a newfound "planet" in our solar system, called 2003 UB<sub>313</sub>, were taken on Oct. 21, 2003, using the Samuel Oschin Telescope at the Palomar Observatory near San Diego, Calif. The planet, circled in white, is seen moving across a field of stars. The three images were taken about 90 minutes apart. Scientists did not discover that the object in these pictures was a planet until Jan. 8, 2005. ''Source: Samuel Oschin Telescope, Palomar Observatory'']]

There has been controversy in the scientific community about what is and what is not a planet. Some purists insist the Solar system has only eight planets and that Kuiper Belt object including Pluto, Sedna and 2003 UB<sub>313</sub> cannot be listed among the major planets.

A minor furor erupted when the IAU suggested removing Pluto from the pantheon of planets a few years ago. Because of that Pluto's status as a "planet" in addition to being a Kuiper Belt object was cemented. But with the discovery of 2003 UB<sub>313</sub> the "planet or not" debate may rekindle.

"Pluto has been a planet for so long that the world is comfortable with that," Brown said in the teleconference. "It seems to me a logical extension that anything bigger than Pluto and farther out is a planet."

Offering additional justification, Brown said 2003 UB<sub>313</sub> appears to be surfaced with methane ice, as is Pluto. That's not the case with other large Kuiper Belt objects, however.

"This object is in a class very much like Pluto," he said.

===A second object found===
The new "10th planet" was not the only new discovery in the Kuiper Belt this past week. [[w:José-Luis Ortiz|José-Luis Ortiz]] at the [[w:Sierra Nevada Observatory|Sierra Nevada Observatory]] in [[w:Spain|Spain]] announced the discovery of an object called [[w:2003 EL61|2003 EL<sub>61</sub>]]. This object, thought to be larger than Sedna, is the brightest trans-Neptune object next to Pluto.

Although some news media confused the discovery of 2003 EL<sub>61</sub> with 2003 UB<sub>313</sub>, they are different objects.

2003 EL<sub>61</sub> is so bright, it can be seen with high-end amateur-grade telescopes equipped with [[w:CCD camera|CCD camera]]s. Although this second discovery may not be as large as 2003 UB<sub>313</sub>, scientists have confirmed that 2003 EL<sub>61</sub> has its own moon.

== Sources ==
*{{source|url=http://www.nytimes.com/2005/07/30/science/30planet.html?hp&ex=1122696000&en=8500b2cc7e8e63c0&ei=5094&partner=homepage
|title=Planet or Not, Pluto Now Has Far-Out Rival
|author=Kenneth Chang and Dennis Overbye
|pub=The New York Times
|date=July 30, 2005}} '''(Free registration required)'''

*{{source|url=http://www.jpl.nasa.gov/news/news.cfm?release=2005-126
|title=Scientists Discover Solar System's Tenth Planet -- Bigger Than Pluto
|author=Press Release
|pub=  NASA
|date=July 30, 2005}}

*{{source|url=http://www.abc.net.au/news/newsitems/200507/s1426220.htm
|title='New planet' found in solar system
|author=
|pub=Australian Broadcasting Company
|date=July 30, 2005}}

*{{source|url=http://english.aljazeera.net/NR/exeres/EC9AFBD2-2455-49AE-B8C5-22059F63DEFE.htm
|title=Time to rewrite textbooks for 'new' planet?
|author=
|pub=Aljazeera
|date=July 30, 2005}}

*{{source|url=http://skyandtelescope.com/news/article_1560_1.asp
|title=Astronomers Discover "10th Planet"
|author=David Tytell 
|pub=Sky and Telescope
|date=July 29, 2005}}

*{{source|url=http://news.bbc.co.uk/2/hi/science/nature/4726733.stm
|title=Distant object found orbiting Sun
|author=Dr. David Whitehouse
|pub=BBC News
|date=July 29, 2005}}

*{{source|url=http://www.gps.caltech.edu/~mbrown/planetlila/index.html
|title=Astronomers at Palomar Observatory Discover a 10th Planet Beyond Pluto
|author=Michael E. Brown
|pub=BBC News
|date=July 29, 2005}}

*{{source|url=http://www.space.com/scienceastronomy/050729_new_planet.html
|title=Object Bigger than Pluto Discovered, Called 10th Planet
|author=Robert Roy Britt
|pub=Space.com
|date=July 29, 2005}}

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[[Category:World]]
[[Category:North America]]
[[Category:Europe]]
[[Category:United States]]
[[Category:Spain]]
[[Category:Science and technology]]
[[Category:Space]]
[[Category:Pluto]]
[[Category:Kuiper belt]]

[[fr:Découverte d'une éventuelle dixième planète du système solaire]]
[[pl:Odkryto dziesiątą planetę Układu Słonecznego]]
[[pt:Nasa descobre décimo planeta do sistema solar]]
[[ca:La NASA hauria descobert el desè planeta del sistema solar]]
[[es: La NASA habría descubierto el décimo planeta del sistema solar]]
[[fr:Découverte d'une éventuelle dixième planète du système solaire]]
[[ja:NASAが発表、太陽系に第10惑星か]]
[[pl:Odkryto dziesiątą planetę Układu Słonecznego]]
[[pt:Nasa descobre décimo planeta do sistema solar]]
The definition of what is and what is not a planet is being challenged by a newly announced discovery Friday. Astronomers from the Palomar Observatory near San Diego, California said they found a chunk of ice and rock in the solar system larger than Pluto.

The object, given the temporary generic name of 2003 UB313, is about 9 billion miles away from the sun. It was first photographed in 2003 using the Gemini Observatory in Hawaii. But it was an indistinguishable bright spot among a field of stars in an area of the sky where astronomers don't usually look at for planets or planet-type objects.

Solar system bodies found beyond the orbit of Neptune are called "trans-Neptunian objects". One of them, Pluto, is also classified as a planet. Up until now all other planet-like discoveries beyond Neptune, including Sedna, found by the same Palomar team in 2004, are called Kuiper Belt objects, or minor planets.

Using mathematical formulas, they found a range of sizes for 2003 UB313, with an estimated average showing the approximate diameter of the new body to be about 2,600 kilometers. But even at the smallest estimate scientists are certain 2003 UB313 is larger than Pluto's 2,250 kilometer diameter.

To determine size, Scientists deduce the relative size of a solar system object by its brightness, just as one can infer the size of a faraway light bulb if one knows its wattage. The reflectance of 2003 UB313 is not yet known for sure. Scientists can not yet tell how much light from the sun is reflected away from its surface, but the amount of light the planet does reflect puts a lower limit on its size.

"Even if it reflected 100 percent of the light reaching it, it would still be as big as Pluto," Michael E. Brown, a professor of planetary astronomy at the California Institute of Technology said in a NASA press release. "I'd say it's probably one and a half times the size of Pluto, but we're not sure yet of the final size."

"We are 100 percent confident that this is the first object bigger than Pluto ever found in the outer solar system," Brown added.

The object is inclined by a whopping 45 degrees to the main plane of the solar system, where most of the other planets orbit. That's why it eluded discovery: nobody was looking there until now, Brown said.

Most objects in the solar system are just a few degrees from the main plane of the solar system, called the Ecliptic.  Pluto, which is considered substantially different from the rest of the planets, is only 17 degrees from this main plane.  Astronomers who study the sky for asteroids and comets usually look in the region of the sky that the rest of the planets occupy.

The brightness of this object is just barely fainter than the telescopes from earlier sky surveys were able to identify, so new advances in the making of telescopes has also played a part in this discovery.

Now that the discovery data has been released, the scientists will turn over their work to the International Astronomical Union (IAU), which will review it, classify the object and approve a new name to replace the temporary 2003 UB313. 

Sometimes the discoverers of a new planetary body get to choose its name, but not always. "We have a name we really like, and we want it to stick," Brown told reporters at a press conference. He said the team has submitted the name to the IAU but would not disclose their choice. In the 2004 naming of Sedna, Brown noted objects found in the Kuiper Belt are usually named after deities of the Underworld. 

The astronomers have been using a code name of sorts for the discovery. The tongue-in-cheek nickname  is "Xena" after the fictional main character of the television series of the same name. "Because we always wanted to name something Xena," Dr. Brown said in a New York Times report.

There has been controversy in the scientific community about what is and what is not a planet. Some purists insist the Solar system has only eight planets and that Kuiper Belt object including Pluto, Sedna and 2003 UB313 cannot be listed among the major planets.

A minor furor erupted when the IAU suggested removing Pluto from the pantheon of planets a few years ago. Because of that Pluto's status as a "planet" in addition to being a Kuiper Belt object was cemented. But with the discovery of 2003 UB313 the "planet or not" debate may rekindle.

"Pluto has been a planet for so long that the world is comfortable with that," Brown said in the teleconference. "It seems to me a logical extension that anything bigger than Pluto and farther out is a planet."

Offering additional justification, Brown said 2003 UB313 appears to be surfaced with methane ice, as is Pluto. That's not the case with other large Kuiper Belt objects, however.

"This object is in a class very much like Pluto," he said.

Although some news media confused the discovery of 2003 EL61 with 2003 UB313, they are different objects.

2003 EL61 is so bright, it can be seen with high-end amateur-grade telescopes equipped with CCD cameras. Although this second discovery may not be as large as 2003 UB313, scientists have confirmed that 2003 EL61 has its own moon.

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__NOTOC__

fr:Découverte d'une éventuelle dixième planète du système solaire
pl:Odkryto dziesiątą planetę Układu Słonecznego
Nasa descobre décimo planeta do sistema solar
ca:La NASA hauria descobert el desè planeta del sistema solar
es: La NASA habría descubierto el décimo planeta del sistema solar
fr:Découverte d'une éventuelle dixième planète du système solaire
ja:NASAが発表、太陽系に第10惑星か
pl:Odkryto dziesiątą planetę Układu Słonecznego
Nasa descobre décimo planeta do sistema solar
World North America Europe United States Spain Science and technology Space Pluto Kuiper belt