The solar system has a 10th planet, an astronomer announced Friday. Larger than Pluto, its highly inclined orbit slings it from its closest approach to the sun — 3.3 billion miles out — to its present location in dark, frigid space 9 billion miles away.
It is presently the most distant identified object in the solar system and takes 560 years to complete one orbit. Yet it is relatively big and bright, within the ability of many advanced amateur astronomers to see and photograph.
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto — and then what? Soon most sixth-graders may be able to complete the list, but for now, the proposed name of the 10th planet is secret.
Michael Brown of the California Institute of Technology announced the find during a telephone press conference Friday afternoon, in which the Deseret Morning News participated. The research was partly funded by NASA, and the press conference was hosted by the agency's Jet Propulsion Laboratory in Pasadena.
Brown said the planet's name won't be released for a while.
"We have submitted a name to the International Astronomical Union, and I don't want to say what it is yet because we really want this name to get accepted," he said. In the world of science, the protocol is to win official acceptance of a name by a governing group such as the IAU before it is released publicly.
Brown and colleagues Chad Trujillo of the Gemini Observatory in Mauna Kea, Hawaii, and David Rabinowitz of Yale University made the discovery Jan. 8 using the 48-inch diameter Samuel Oschin Telescope at Mount Palomar Observatory in California. In a survey for distant objects, they actually had photographed the planet on Oct. 31, 2003, but it was not recognized until recently.
By strange coincidence, two other large, distant objects were announced about the same time. Spanish astronomers announced one on Thursday, and Brown also announced another Friday besides the 10th planet. Brown said his group also had been following the object announced by the Spaniards, and they were able to calculate its size as three-quarters that of Pluto.
All three apparently are members of the Kuiper belt of comet-like material that orbits the sun in the distant solar system. But only the one temporarily designated 2003-UB313 is larger than Pluto.
The 10th planet, Brown said, is definitely larger than the ninth (Pluto,) based on measurements of its brightness and other factors. If it were to reflect 100 percent of the sunlight hitting it, which is an impossibility, it would be the size of Pluto. If it were to reflect half the sunlight hitting it, it would be 1,864 miles across.
However, the Spitzer Space Telescope could not detect it. That means it probably is less than 1,854 miles in diameter. Other studies show that its surface is, like Pluto's, covered with frozen methane.
"It is a very cold, very distant place. If you were standing at the surface and you held a pin at arms length you could cover the sun with the head of the pin."
Why call it a planet?
"I think any reasonable definition that includes the nine planets we know has to include anything bigger," Brown said.
He added that he used to argue that Pluto, because of its diminutive size, should not be considered a planet. But then he researched the matter and realized that the public loves Pluto and would not accept a demotion.
The IAU also has accepted Pluto as a planet.
Friday's announcement was rushed, Brown indicated.
"We have been intending to announce this in a couple of months when we had completed our studies for it, and somebody hacked our Web site," he said. Apparently the hacker, whom he described as having "more cleverness than scruples," intended to tell the world of the discovery before the scientists could.
"As soon as we realized that somebody had ahold of our data and was trying to make it public, the group knew they had no choice but to make it public immediately," Brown said.
All three objects that have been identified approach the sun to about 36 astronomical units (AU), he said. An astronomical unit is the distance from the sun to the Earth — 93 million miles.
When a News reporter asked why all their orbits reach 36 AU, Brown said that is typical of some objects in the Kuiper Belt.
Apparently the planet Neptune, at 30 AU the most distant large planet known, has encounters with Kuiper Belt objects, flinging into more and more elliptical orbits. That seems to have happened with the new planet, he said, "except that the 10th planet has a higher inclination than almost anything else in the solar system."
In other words, Neptune's gravity apparently flung the 10th planet into an orbit reaching far above the plane of the other planets of the solar system. It is inclined at almost 45 degrees to the other main planets. Another exception is Pluto, which is inclined, but not nearly as much as the new planet.
As it is now at its farthest location, in 280 years it will reach its closest point to the sun.
Brown said he had a bet with a friend that the survey would discover a planet larger than Pluto within five years. The five years were up on Jan. 1. The discovery was made on Jan. 8.
His first reaction was that he had lost the bet by seven days. Then he called his wife and told her of the find. "I was just on cloud nine. It was almost as exciting as knowing we were going to have a daughter this summer."
Patrick Wiggins, NASA solar system ambassador to Utah, was excited by the announcement.
"I've heard this so many times before, you know, '10th planet found.' But this is the first one in all of the years that actually smells right. It's got a good pedigree behind it." The scientists making the discovery know what they're doing, he said.
Wiggins, who has contended that maybe Pluto ought not to be considered a planet, joked that with the discovery of this larger object, "we have nine planets!"
He is excited about looking for the new one with his telescope, as soon as the weather clears up.
"The solar system," Wiggins said, "just keeps getting bigger."
E-mail: bau@desnews.com