First a Slashdot comment, than the 'new planet discovered' news.
J.
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Perhaps a New King of the Kuiper Belt(Score:5, Informative)
by rwllama (587787)
Friday July 29, 2005
SourceAmongst professional astronomers (which includes me), Pluto is generally not considered a planet. It is the largest member of the Kuiper Belt. It is historical accident that Pluto was discovered almost 50 years before the second Kuiper Belt object, Charon, in 1978. The third KBO was found in 1993. Since then, over 700 other KBOs have been found, several of which rival Pluto in size.
What we have here is one that could be larger than Pluto. This is not unexpected, but has been predicted ever since we started discovering KBOs in serious numbers. There is always a distribution of sizes, and Pluto lies near the upper end, but it is unlikely that it is the largest, and even less likely that it would be distinctly larger than the rest of the population.
To call Pluto a planet is to create a category of "ice planets" which contains only one object. That is scientifically silly. To call it a Kuiper Belt Object fits it in with a family of other objects whose characteristics in composition, orbit size, orbit shape, orbit inclination, companions, etc are shared amongst the group. That is a scientific classification.
The solar system does not contain "the Sun and 9 planets" as so many of us incorrectly learned. Rather, it contains 6 families: a star, the rocky planets, the asteroid belt, the gas giant planets, the Kuiper belt, and the Oort cloud. Each of these families shares common characteristics that are the basis for this classification. Pluto, and this new discovery,
fit squarely in the Kuiper belt.
Now for the truth about planets. The IAU, which governs these things, has no official definition of what constitutes a planet. There is a reasonable upper limit in mass (i.e., not so larger as to create fusion at it core), but there is no lower limit. Most astronomers would say that a reasonable idea would be large enough for gravity to make it spherical (or close to, like Earth). However, then other KBOs and asteroids qualify as planets. You simply can't come up with a rigorous definition that includes Pluto and excludes the others unless you work customize your definition in a manner that is not scientific.
This will not be the last big KBO. There will be several more. These are exciting times as we discover more and more about our own backyard.
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Large New World Discovered Beyond NeptuneBy Robert Roy Britt
Senior Science Writer
posted: 29 July 2005
SourceA newfound object in our solar system's outskirts may be larger than any known world after Pluto, scientists said today.
It also has a moon.
Designated as 2003 EL61, the main object in the two-body system is 32 percent as massive as Pluto and is estimated to be about 70 percent of Pluto's diameter.
Other news reports that the object could be twice as big as Pluto are false, according to two astronomers who found the object in separate studies and another expert who has analyzed the data.
If the mass is only one-third that of Pluto, then theory holds that it can't be larger than Pluto, according to Brian Marsden of the Minor Planet Center, which serves as a clearinghouse for data on all newfound objects in the solar system.
Marsden, who was not involved in the discovery but has reviewed the data, told SPACE.com that the mass estimate is very firm, within 1 or 2 percent. "I don’t think it is bigger than Pluto," he said.
Where it fits inThis is still a big world, once again raising the prospect that something larger than Pluto might still lurk out there.
Scientists base their size calculations in part on the object's reflectivity. Since they don't know exactly how much the surface brightness of distant objects varies, there is some wiggle room in their size estimates.
A team led by Mike Brown of Caltech has been observing 2003 EL61 for a year but was seeking more data before announcing the discovery. Brown said today it may possibly be larger than Sedna, which has been the largest known world beyond Neptune other than Pluto.
Sedna is between 800 and 1,100 miles in diameter. Pluto is about 1,400 miles across.
Brown figures 2003 EL61 has a diameter of around 930 miles.
Is there any chance it is bigger than Pluto?
"No," Brown said in a telephone interview. "Definitely not."
In fact, Brown's team got the new data they had been waiting for, from the Spitzer Space Telescope, last week. While not fully analyzed, he said the Spitzer observations show "absolutely" that the object is not bigger than Pluto.
Who gets credit?The object was spotted independently by a group led by Jose-Luis Ortiz of the Sierra Nevada Observatory in Spain. Ortiz' team announced the finding in astronomy circles recently and the finding, including the claim that it might be twice as big as Pluto, was reported by an online news site today.
Ortiz said that based on his team's observations, there was one outlying theory could allow 2003 EL61 to be larger than Pluto, but he does not think it is right.
"I do not think it is larger than Pluto," Ortiz told SPACE.com today.
Brown was surprised last night to learn that Ortiz' group had independently found the object, which only yesterday gained the tag 2003 EL61 from the Minor Planet Center. It was a rare case of one group of astronomers unwittingly scooping another.
Brown said that Ortiz' group rightfully deserves credit for making the discovery.
About that moon2003 EL61 orbits the Sun on an elliptical path beyond Neptune in a region of space known as the Kuiper Belt. It is significantly inclined to the main plane of the solar system where most of the planets travel. It is one of several objects out there now known to have a satellite.
The moon around 2003 EL61 is small, making up only about 1 percent of the mass of the system, Brown said.
"This satellite is the smallest satellite relative to its primary known in the Kuiper belt," Brown said. "Pluto's satellite, Charon, is about 10 percent of the mass of Pluto.
Marsden, of the Minor Planet Center, said it is surprising the object was not discovered earlier. He said it was probably just barely too faint to be spotted in the sky survey done by Clyde Tombaugh that led to the discovery of Pluto 75 years ago.
Brown's team first spotted 2003 EL61, which had no name at the time, using the Samuel Oschin Telescope at Palomar Observatory on May 6, 2004. They did not realized they had found it until Dec. 28, 2004, after scrutinizing their data in and ongoing effort to find Kuiper Belt Objects.
In a series of three images, the object is seen moving across the sky in relation to relatively fixed background stars.
Ortiz's group initially detected the object in 2003 and spotted it again this year, leading to their announcement yesterday.