New planet could be earthlike, scientists say

The most enticing property yet found outside our solar system is about 20 light-years away in the constellation Libra, a team of European astronomers said Tuesday.

The astronomers have discovered a planet five times as massive as the Earth orbiting a dim red star known as Gliese 581.

It is the smallest of the 200 or so planets that are known to exist outside of our solar system, the extrasolar or exo-planets. It orbits its home star within the so-called habitable zone where surface water, the staff of life, could exist if other conditions are right, said Dr. Stephane Udry of the Geneva Observatory.

"We are at the right place for that," said Udry, the lead author of a paper describing the discovery that has been submitted to the journal Astronomy & Astrophysics.

But he and other astronomers cautioned that it was far too soon to conclude that liquid water was there without more observations. Sara Seager, a planet expert at the Massachusetts Institute of Technology, said, "For example, if the planet had an atmosphere more massive than Venus's, then the surface would likely be too hot for liquid water."

Nevertheless, the discovery in the Gliese 581 system, where a Neptune-size planet was discovered two years ago and another planet of eight Earth masses is now suspected, catapults that system to the top of the list for future generations of space missions.

"On the treasure map of the universe, one would be tempted to mark this planet with an X," said Xavier Delfosse, a member of the team from Grenoble University in France, according to a news release from the European Southern Observatory, a multinational collaboration based in Garching, Germany.

Dr. Dimitar Sasselov of the Harvard-Smithsonian Center for Astrophysics, who studies the structure and formation of planets, said: "It's 20 light-years. We can go there."

The new planet was discovered by the wobble it causes in its home star's motion as it orbits, using the method by which most of the known exo-planets have been discovered. Udry's team used an advanced spectrograph on a 141-inch-diameter telescope at the European observatory in La Silla, Chile.

The planet, Gliese 581c, circles the star every 13 days at a distance of about seven million miles. According to models of planet formation developed by Sasselov and his colleagues, such a planet should be about half again as large as the Earth and composed of rock and water, what the astronomers now call a "super Earth."

The most exciting part of the find, Sasselov said, is that it "basically tells you these kinds of planets are very common." Because they could stay geologically active for billions of years, he said he suspected that such planets could be even more congenial for life than Earth. Although the new planet is much closer to its star than Earth is to the Sun, the red dwarf Gliese 581 is only about a hundredth as luminous as the Sun. So seven million miles is a comfortable huddling distance.

How hot the planet gets, Udry said, depends on how much light the planet reflects, its albedo. Using the Earth and Venus as two extreme examples, he estimated that temperatures on the surface of the planet should be in the range of 0 degrees to 40 degrees centigrade.

"It's just right in the good range," Udry said. "Of course, we don't know anything about its albedo."

One problem is that the wobble technique only gives masses of planets. To measure their actual size and thus find their densities, astronomers have to catch the planets in the act of passing in front of or behind their stars. Such transits can also reveal if the planets have atmospheres and what they are made of.

Udry said he and Sasselov would be observing the Gliese system with a Canadian space telescope named MOST to see if there are any dips in starlight caused by the new planet. Failing that, they said, the best chance for more information about the system lies with the Terrestrial Planet Finder, a NASA mission, and the Darwin missions of the European Space Agency, which are designed to study Earthlike planets, but have been delayed by political, technical and financial difficulties.

"We are starting to count the first targets," Udry said.

Bush says talks with Iran possible

Tue, April 24, 2007

NEW YORK -President Bush said Tuesday that Secretary of State Condoleezza Rice might have one-on-one talks with Iranian leaders at an international conference on Iraq next month, but that Tehran's nuclear program would not be on the table.

In an interview, Bush initially appeared to rule out any contact with Iran, a member of his "axis of evil."

"What I'm not willing to do is sit down bilaterally with the Iranians," he told PBS' "The Charlie Rose Show."

Later, he said Rice and Iran's foreign minister might have bilateral conversations at the conference. "They could. They could," Bush said.

The United States cut diplomatic ties with Iran following the 1979 storming of the U.S. Embassy in Tehran. Although there have been periodic diplomatic contacts, the Bush administration has resisted pressure at home and abroad to engage Iran one-on-one in an effort to improve security in neighboring Iraq.

That policy began to change this spring. Although it is not inviting a broad conversation, the administration has repeatedly said it will not rule out sideline talks with either Iran or Syria at the conference May 3-4 at Egypt's Red Sea resort of Sharm el-Sheik.

Such contact would follow the model established last month when lower-level State Department officials had cordial discussions with Iranian and Syrian diplomats.

It is not clear whether Iran will attend the May session, however, and State Department spokesman Sean McCormack seemed to lower expectations Tuesday.

"I don't foresee it," McCormack said in an interview, adding that he would not rule it out.

Bush said if a meeting occurs, Rice's message to the Iranians would be: "Don't send weapons in (to Iraq) that will end up hurting our troops, and help this young democracy survive."

Bush said that if he thought separate one-on-one discussions with the Iranians would convince them to give up their alleged nuclear weapons ambitions, he would consider the idea.

"I don't believe a discussion with Iran alone, and at this moment in time, would yield the result we want," Bush said.

Powers consider Iran nuclear proposal

By GEORGE JAHN, Associated Press Writer Tue Apr 24, 2007

ANKARA, Turkey - The United States and other world powers may be ready to allow Iran to keep some of its uranium enrichment program intact instead of demanding its complete dismantling, foreign government officials said Tuesday.

Officials said some willingness to compromise might advance talks Wednesday in the Turkish capital between top Iranian envoy Ali Larijani and Javier Solana, the
European Union's foreign policy chief.

Recognizing that Iran would never accept a complete freeze, the powers are considering "a new definition of enrichment," one diplomat said. Under the proposal, Iran would could keep some of its program intact without actually producing enriched uranium.

State Department spokesman Sean McCormack denied that the United States was "considering any proposals that would allow the Iranians to retain any enrichment-related activities."

But another U.S. official who spoke on condition of anonymity suggested there was potentially more flexibility in Washington's position than previously.

"We purposely left open the possibility that direct talks could happen by being a little less committed to the requirements to have a meeting," said the official. He alluded to previous demands of an all-encompassing freeze on all enrichment related activities.

Iran is running more than 1,300 centrifuge machines at its underground facility at Natanz. Its ultimate goal is to run 50,000 centrifuges a year, enough to churn out material for a network of nuclear power generators — or a full-scale nuclear weapons program.

The United States might accept a version of "cold standby" — allowing a set number of centrifuges to remain standing and assembled in series but not running, a diplomat said. Iran, he said, would likely push for keeping the machines operating, if not producing enriched uranium.

The six powers — United States, Russia, China, Britain, France and Germany — also want to reduce assembled and hooked-up centrifuges to less than 1,000.

A European official said hopes were that both sides could agree on at least "a different definition of suspension that we can work with."

Like other officials — some of them diplomats, others based in their capitals — the two spoke to The Associated Press on condition of anonymity because they were discussing confidential information.

With agreement to strive for a new definition of enrichment, Larijani and Solana may be able to sidestep a deadlock that for months has thwarted the resumption of negotiations over Iran's nuclear program, said the officials, who were familiar with the discussions with Iran or specialized in non-proliferation issues.

Iran's defiance of a U.N. Security Council demand to suspend all activities linked to enrichment — a possible pathway to nuclear arms — has led to two sets of sanctions against the country, the latest last month.

Iran argues the sanctions are illegal, noting it has the right to enrich uranium to generate nuclear power under the Nuclear Non-Proliferation Treaty. Iranian officials say nuclear power is the only purpose of their program, rejecting suspicions that they ultimately want weapons-grade uranium for the fissile core of nuclear warheads.

But the United States and others say past suspicious nuclear activities, including a program Iran kept secret for nearly two decades, set the country apart from others that have endorsed the treaty.

The last face-to-face talks between Solana and Larijani were more than six months ago, and foundered over the same issue. Solana, representing the six powers, demanded that Iran dismantle not only fledging enrichment efforts but all linked aspects, including assembling centrifuges for enrichment and facilities to house such plants. Iran refused.

Negotiations between Iran and the three European nations broke down last year when the Iranian government refused to suspend enrichement in exchange for a package of economic and political inducements, including help in developing a peaceful nuclear program.

One of the diplomats said recognition by the United States and its allies that Iran would never accept their earlier demand of a full freeze dictated a decision to contemplate "a new definition of enrichment" that would allow Tehran to keep some of its program intact without actually turning out enriched material.

An agreement was unlikely be emerge from Wednesday's talks. Solana would have to report back to the six capitals he is representing, while Larijani would need to have any deal cleared with the Iranian government.