10th planet discovered
Behind the news is a scientific controversy that gives a headache to anyone who starts thinking about it seriously.
What is a planet? What is the difference between a "minor planet" - an asteroid, a Kuiper Belt object - and a planet like the one we know from reading a textbook?
Many astronomers think that Pluto is not a planet. Why? Its orbit doesn't follow the ecliptic. The ecliptic is the geometric plane that contains the orbit of the Earth. The orbits of most planets in the Solar System lie very close to it.
The thing is it's pretty to unfair to doubt that Pluto and "2003 UB313" are planets for the only reason they don't move straight enough in the sky. These worlds are huge. Their diameters exceed 2,000 Km (1,300 miles). Such a big size make them look round-shaped like any other planets.
Why is it an issue? To call an object a planet means it will be given the fame that Pluto gets in any textbook. If Pluto had been called an asteroid (or Kuiper Belt Object), students would not learn anything about it.
Scientists Discover Solar System's Tenth Planet -- Bigger Than Pluto
A planet larger than Pluto has been discovered in the outlying regions of the solar system
The planet was discovered using the Samuel Oschin Telescope at Palomar Observatory near San Diego, Calif. The discovery was announced today by planetary scientist Dr. Mike Brown of the California Institute of Technology in Pasadena, Calif., whose research is partly funded by NASA.
The planet is a typical member of the Kuiper belt, but its sheer size in relation to the nine known planets means that it can only be classified as a planet, Brown said. Currently about 97 times further from the sun than the Earth, the planet is the farthest-known object in the solar system, and the third brightest of the Kuiper belt objects.
"It will be visible with a telescope over the next six months and is currently almost directly overhead in the early-morning eastern sky, in the constellation Cetus," said Brown, who made the discovery with colleagues Chad Trujillo, of the Gemini Observatory in Mauna Kea, Hawaii, and David Rabinowitz, of Yale University, New Haven, Conn., on January 8.
Brown, Trujillo and Rabinowitz first photographed the new planet with the 48-inch Samuel Oschin Telescope on October 31, 2003. However, the object was so far away that its motion was not detected until they reanalyzed the data in January of this year. In the last seven months, the scientists have been studying the planet to better estimate its size and its motions.
"It's definitely bigger than Pluto," said Brown, who is a professor of planetary astronomy.
Scientists can infer the 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 the planet is not yet known. Scientists can not yet tell how much light from the sun is reflected away, but the amount of light the planet reflects 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," says Brown. "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 size of the planet is limited by observations using NASA's Spitzer Space Telescope, which has already proved its mettle in studying the heat of dim, faint, faraway objects such as the Kuiper-belt bodies. Because Spitzer is unable to detect the new planet, the overall diameter must be less than 2,000 miles, said Brown.
A name for the new planet has been proposed by the discoverers to the International Astronomical Union, and they are awaiting the decision of this body before announcing the name.
The Jet Propulsion Laboratory manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Caltech manages JPL for NASA.
For more information and images see: http://www.nasa.gov/vision/universe/solarsystem/newplanet-072905-images.html
For information about NASA and agency programs on the Web, visit:
Editor's Note: The original news release can be found here
Caltech astronomer finds solar system's 10th planet
Sat Jul 30, 2005 2:50 AM BST
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By Gina Keating
LOS ANGELES (Reuters) - A California astronomer has discovered what he believes is the 10th planet in our solar system, a group of NASA-funded researchers said on Friday.
The new planet, known as 2003UB313, has been identified as the most distant object ever detected orbiting the sun, California Institute of Technology astronomer Michael Brown said.
Brown and colleagues Chad Trujillo and David Rabinowitz have submitted a name for the planet to the International Astronomical Union and are confident it will be designated a planet. Brown did not reveal the proposed name.
The procedure for approving the new planet is somewhat hazy as no new bodies have received that designation since Pluto was discovered in 1930, Brown said.
"We hope that it's fairly noncontroversial among those who believe Pluto is a planet," Brown said. "I would say get out your pens and start rewriting the textbooks today."
The planet is located about 9.7 billion miles from the sun and is about 1 1/2 times the size of Pluto, the researchers said.
The new planet orbits the sun once every 560 years and is now at its farthest point from Earth, he said. In about 280 years, the planet will be as close as Neptune, he said.
Like Pluto, the object's surface is believed to be predominantly methane, but its size -- about 1,700 miles in diameter -- qualifies it as a planet, Brown said. Earth is about 7,900 miles in diameter.
The new planet is believed to be part of the Kuiper Belt, a large ring of icy objects that orbit beyond Neptune and are believed to be remnants of the material that formed the solar system.
Brown said the new planet was detected in January by the Samuel Oschin Telescope at the Palomar Observatory near San Diego.
The Caltech team, funded in part by NASA, had been waiting to announce the find until they had completed their studies, but changed their minds after a hacker threatened to go public with their data, Brown said.
Their finding comes a day after a Spanish team of astronomers announced the discovery of another relatively large object orbiting in the solar system's outer reaches. That object, Brown said, was about three-quarters the size of Pluto.
The new planet went undiscovered for so long because its orbit is tilted at a 45-degree angle to the orbital plane of the other planets, and travels in an elliptical orbit, Brown said.
The team had been scanning the skies with the 48-inch (120-cm) telescope for five years, searching for large bodies orbiting in higher planes than that of the Earth and other planets.
The new planet is so far away that an observer standing on its surface could cover the view of the sun with the head of a pin, Brown said. It was sufficiently bright, however, for amateur astronomers to track it in the early morning sky, he said. © Reuters 2005. All Rights Reserved.
Planet or Not, Pluto Now Has Far-Out Rival
By KENNETH CHANG and DENNIS OVERBYE
Published: July 30, 2005
Add a tenth planet to the solar system - or possibly subtract one.
Astronomers announced yesterday that they had found a lump of rock and ice that was larger than Pluto and the farthest known object in the solar system. The discovery will probably rekindle debate over the definition of "planet" and whether Pluto still merits the designation.
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A Distant Neighbor, Possibly
Forum: Space and the Cosmos
The new object - as yet unnamed, but temporarily known as 2003 UB313 - is now 9 billion miles away from the Sun, or 97 times as far away as Earth and about three times Pluto's current distance from the Sun. Its 560-year elliptical orbit brings it as close as 3.3 billion miles. Pluto's orbit ranges from 2.7 billion miles to 4.6 billion.
The astronomers do not have an exact size for the new planet, but its brightness and distance tell them that it is larger than Pluto, the smallest of the nine known planets.
"It is guaranteed bigger than Pluto," said Michael E. Brown, a professor of planetary astronomy at the California Institute of Technology and a member of the team that made the discovery. "Even if it were 100 percent reflective, it would be larger than Pluto. It can't be more than 100 percent reflective."
The discovery was made Jan. 8 at Palomar Observatory in California. Dr. Brown and the other members of the team - Chadwick A. Trujillo of the Gemini Observatory in Hawaii and David L. Rabinowitz of Yale University - then found that they had, unknowingly, taken images of the planet, using the observatory's 48-inch telescope, as far back as 2003.
Last year, the same team announced the discovery of a distant body they named Sedna, which, until the latest discovery, had held the title of farthest known object in the solar system. But Sedna, smaller than Pluto, is on a far stranger, 10,500-year orbit that takes it as far out as 84 billion miles.
Dr. Brown said they had a name they have proposed for the planet, but did not want to disclose it until it had been formally approved by the International Astronomical Union. "We have a name we really like, and we want it to stick," he said.
Informally, the astronomers have been calling it Xena after the television series about a Greek warrior princess, which was popular when the astronomers began their systematic sweep of the sky in 2000. "Because we always wanted to name something Xena," Dr. Brown said.
The astronomers were not able to see 2003 UB313 using NASA's Spitzer Space Telescope, looking for infrared heat emitted by its minus-405 degree surface. That means the planet is less than 1,800 miles in diameter.
What is most surprising is that the orbit of the planet is sharply skewed to most of the rest of the solar system. The orbits of most planets lie close to the same plane as Earth's, known as the ecliptic plane. The orbit of 2003 UB313 is tilted by 44 degrees.
"That blows my mind," said Harold Levison of the Southwest Research Institute in Boulder, Colo., who was not involved in the discovery. "Getting something up that high is very hard."
The object is also the third brightest in the Kuiper Belt, a ring of icy bodies that circles beyond Neptune. The new planet could have been easily discovered much sooner if anyone had looked at that part of the sky.
"It's because no one looks that far off the ecliptic," Dr. Brown said. "No one expects to have an inclination that high."
Another group of astronomers led by José-Luis Ortiz at the Sierra Nevada Observatory in Spain announced Thursday that they had found a large Kuiper Belt object, designated 2003 EL61, that they thought could be Pluto-size or larger. Dr. Brown's group had been observing the same body, but had not announced it, and their observations had already pinpointed a moon circling 2003 EL61, which constrained the size of the body to 30 percent the mass of Pluto and about 70 percent the diameter.
On his Web site, Dr. Brown wrote that the Spanish group deserved credit, saying his group had gambled that no one else would find the planet. "We were wrong!" he said.
Dr. Brown had still hoped to hold back announcements of 2003 UB313 and another large Kuiper Belt object, 2005 FY9, until October, but his hand was tipped by Brian G. Marsden, director of the International Astronomical Union's Minor Planet Center in Cambridge, Mass., who urged him to make the announcement as soon as possible.
BREAKING NEWS: Object Bigger than Pluto Discovered, Called 10th Planet By Robert Roy BrittSenior Science Writerposted: 29 July 200507:59 pm ET
Updated at 11:17 p.m. ET :
Astronomers have discovered an object in our solar system that is larger than Pluto. They are calling it the 10th planet, but already that claim is contested.
The new world's size is not at issue. But the very definition of planethood is.
Announcement made in haste after discoverer's web site hacked
If it's a planet, it is not No. 10, other astronomers say
Next up: Mars-sized objects?
Amateur astronomers can observe 2003 UB313
It is the first time an object so big has been found in our solar system since the discovery of Pluto 75 years ago.
The announcement, made today by Mike Brown of Caltech, came just hours after another newfound object, one slightly smaller than Pluto, was revealed in a very confusing day for astronomers and the media.
The new object, temporarily named 2003 UB313, is about three times as far from the Sun as is Pluto.
"It's definitely bigger than Pluto," said Brown, a professor of planetary astronomy. The object is round and could be up to twice as large as Pluto, Brown told reporters in a hastily called NASA-run teleconference Friday evening.
His best estimate is that it is 2,100 miles wide, about 1-1/2 times the diameter of Pluto.
One of many?
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.
Some astronomers view it as a Kuiper Belt object and not a planet. The Kuiper Belt is a region of frozen objects beyond Neptune.
Pluto is called a Kuiper Belt object by many astronomers. Brown himself has argued in the past for Pluto's demotion from planet status, because of its diminutive size and eccentric and inclined orbit.
But today he struck a different note.
"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.
NASA effectively endorsed the idea in an official statement that referred to 2003 UB313 as the 10th planet.
Yet in recent years, a bevy of objects roughly half to three-fourths the size of Pluto have been found.
No definition for 'planet'
Brian Marsden, who runs the Minor Planet Center where data on objects like this are collected, says that if Pluto is a planet, then other round objects nearly as large as Pluto ought to be called planets. On that logic, 2003 UB313 would perhaps be a planet, but it would have to get in line behind a handful of others that were discovered previously.
"I would not call it the 10th planet," Marsden told SPACE.com.
Alan Boss, a planet-formation theorist at the Carnegie Institution of Washington, called the discovery "a major step." But Boss would not call it a planet at all. Instead, he said Pluto and other small objects beyond Neptune should be called, at best, "Kuiper Belt planets."
"To just call them planets does an injustice to the big guys in the solar system," Boss said in a telephone interview.
The very definition of what constitutes a planet is currently being debated by Boss and others in a working group of the International Astronomical Union. Boss said the group has not reached consensus after six months of discussion.
The debate actually stretches back more than five years and is rooted in the fact that astronomers have never had a definition for the word "planet," because the nine we knew seemed obvious.
"This discovery will likely re-ignite a healthy debate about what is and what is not a planet," Boss said.
Next up: Mars-sized objects?
Alan Stern, of the Southwest Research Institute and leader of NASA's New Horizons mission to Pluto, predicted in the early 1990s that there would be 1,000 Plutos out there. He has also contended, based on computer modeling, that there should be Mars-sized worlds hidden in the far corners of our solar system and even possibly other worlds as large as Earth.
In a telephone interview after Friday's announcement, Stern, who was not involved in the discovery, said he stands by those predictions and expects Mars-sized objects to be found within decades.
"I find this to be very satisfying," Stern said of 2003 UB313. "It's something we've been looking for for a long time."
Stern stopped short of calling it one of the greatest discoveries in astronomy, however, because he sees it as just one more of many findings of objects in this size range. Last year, for example, Brown's team found Sedna, which is about three-fourths as large as Pluto. Others include 2004 DW and Quaoar.
Stern sees the outer solar system as an attic full of undiscovered objects.
"Now we have the technology to see them," he said. "We're just barely scratching the surface."
Way out there
The new world is about 97 astronomical units from the Sun. An astronomical unit is the distance between the Sun and Earth. It becomes the farthest-known object in the solar system, and the third brightest of the Kuiper belt objects.
It is colder than Pluto and "not a very pleasant place to be."
It was found using the Samuel Oschin Telescope at Palomar Observatory.
Backyard astronomers with large telescopes, some experience and a map may be able to spot 2003 UB313.
Brown said it will be a very exciting object to explore since professionals and amateurs both have access to it.
"It will be visible over the next six months and is currently almost directly overhead in the early-morning eastern sky, in the constellation Cetus," says Brown, who made the discovery with colleagues Chad Trujillo, of the Gemini Observatory, and David Rabinowitz, of Yale University, on Jan. 8.
The team had hoped to analyze the data further before announcing the planet but were forced to do so Friday evening because word had leaked out, Brown said.
"Somebody hacked our website," he said, and "they were planning to make [the data] public."
Brown and Trujillo first photographed the new planet with the 48-inch Samuel Oschin Telescope on Oct. 31, 2003. However, the object was so far away that its motion was not detected until they reanalyzed the data in January of this year. In the last seven months, the scientists have been studying the planet to better estimate its size and its motions.
Scientists infer the size of a solar-system object by its brightness and distance. The reflectiveness of the new planet is not known, however, which is why the estimate of its diameter ranges from one to two times the size of Pluto. But those constraints are well supported by the data, Brown said.
"Even if it reflected 100 percent of the light reaching it, it would still be as big as Pluto," says Brown. "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. But we are 100 percent confident that this is the first object bigger than Pluto ever found in the outer solar system."
The upper size limit is constrained by results from the Spitzer Space Telescope, which records heat in the form of infrared light. Because the Spitzer can't detect the new planet, the overall diameter must be less twice Pluto's size, Brown said.
Brown has had a running bet for five years with a friend that an object larger than Pluto would be found by Jan. 1 this year. 2003 UB313 was spotted on Jan. 8.
"My first reaction was, 'aw, I lost the bet by seven days,'" he said.
Brown's team has submitted a name proposal to the International Astronomical Union and has chosen not to divulge it until that body makes a decision.
Astronomers detect '10th planet'
By Dr David Whitehouse Science Editor BBC news website
The new planet has a highly-inclined orbitAstronomers in the United States have announced the discovery of the 10th planet to orbit our Sun.
The largest object found in our Solar System since the discovery of Neptune in 1846, it was first seen in 2003, but only recently confirmed as a planet.
Designated 2003 UB313, it is about 3,000km across, a world of rock and ice and somewhat larger than Pluto.
It is more than twice as far away as Pluto, in a puzzling orbit, at an angle to the orbits of the other planets.
Astronomers think that at some point in its history Neptune likely flung it into its highly-inclined 44 degree orbit.
It is currently 97 Earth-Sun distances away - more than twice Pluto's average distance from the Sun.
Bigger than Pluto
Its discoverers are Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory in Hawaii and David Rabinowitz of Yale University.
It's not every day that you find something Pluto-sized or larger!
Chad TrujilloDavid Rabinowitz told the BBC News website: "It has been a remarkable day and a remarkable year. 2003 UB313 is probably larger than Pluto. It is fainter than Pluto, but three times farther away.
"Brought to the same distance from the Sun as Pluto, it would be brighter. So today the world knows that Pluto is not unique. There are other Plutos, just farther out in the solar system where they are a little harder to find."
It was picked up using the Samuel Oschin Telescope at Palomar Observatory and the 8-metre Gemini North telescope on Mauna Kea.
Chad Trujillo told the BBC News website: "I feel extremely lucky to be part of a discovery as exciting as this. It's not every day that you find something Pluto-sized or larger!"
"The spectra that we took at the Gemini Observatory are particularly interesting because it shows that the surface of 2003 UB313 is very similar to that of Pluto."
It was first seen 21 October 2003, but didn't see it move in the sky until looking at the same area 15 months later on 8 January 2005.
The researchers say they tried looking for it with the Spitzer Space Telescope which is sensitive to heat radiation, and didn't detect it.
This gives them an upper limit of its size of 3,000 km, they say. The lower limit still makes it larger than Pluto.
The discovery of 2003 UB313 comes just after the announcement of the finding of 2003 EL61, which appears to be a little smaller than Pluto.