Earth-like planet discovered 50 light-years away
Planet is smallest known outside our solar system
By Robert Roy Britt
SPACE.com



(SPACE.com) -- In a discovery that has left one expert stunned, European astronomers have found one of the smallest planets known outside our solar system, a world about 14 times the mass of our own around a star much like the sun.

It could be a rocky planet with a thin atmosphere, a sort of "super Earth," the researchers said today.

But this is no typical Earth. It completes its tight orbit in less than 10 days, compared to the 365 required for our year. Its daytime face would be scorched.

The planet's surface conditions aren't known, said Portuguese researcher Nuno Santos, who led the discovery. "However, we can expect it to be quite hot, given the proximity to the star."

Hot as in around 1,160 degrees Fahrenheit (900 Kelvin), Santos said.

Still, the discovery is a significant advance in technology: No planet so small has ever been detected around a normal star. And the finding reveals a solar system more similar to our own than anything found so far.

Terrestrial in nature
The star is like our sun and just 50 light-years away. A light-year is the distance light travels in a year, about 6 trillion miles (10 trillion kilometers). Most of the known extrasolar planets are hundreds or thousands of light-years distant.

The star, mu Arae, is visible under dark skies from the Southern Hemisphere. It harbors two other planets. One is Jupiter-sized and takes 650 days to make its annual trip around the star. The other planet, whose existence was confirmed with the help of the new observations, is farther out.

The three-planet setup, with one being rocky, is unique.

"It's much closer to our solar system than anything we've found so far," said Alan Boss, a planet-formation theorist at the Carnegie Institution in Washington.

"This really is an exciting discovery," said Boss, who was not involved in the work. "I'm still somewhat stunned they have such good data."

The discovery was made with a European Southern Observatory telescope at La Silla, Chile, working at the verge of what's possible to detect.

Most of the more than 120 planets found beyond our solar system are gaseous worlds as big or larger than Jupiter, mostly in tight orbits that would not permit a rocky planet to survive.

A handful of planets smaller than Saturn have been found, but none anywhere near as small as the one announced today. And a trio of roughly Earth-sized planets was found in 2002 to orbit a dense stellar corpse known as a neutron star. They are oddballs, however, circling rapidly around a dark star that would not support life. Some planet hunters don't consider these three to be as important as planets around normal stars.

At 14 times the mass of Earth, the newfound planet -- circling a star similar in size and brightness to our sun -- is about as heavy as Uranus, a world of gas and ice and the smallest giant planet in our solar system. Theorists say 14 Earth-masses is roughly the upper limit for a planet to possibly remain rocky, however. And because this planet is so close to its host star, it likely had a much different formation history than Uranus.

In our solar system, the four innermost planets are all rocky.

Rock and air
The leading theory of planet formation has the gas giants forming from a rocky core, a process in which the core develops over time, then reaches a tipping point when gravity can rapidly collect a huge envelope of gas. This theory suggests the newfound planet never reached that critical mass, said Santos, of the Centro de Astronomia e Astrofisica da Universidade de Lisboa, Portugal.

"Otherwise the planet would have become much more massive," Santos said via e-mail.

"This object is therefore likely to be a planet with a rocky core surrounded by a small gaseous envelope and would therefore qualify as a super-Earth," the European team said in a statement.

In a telephone interview, Boss of the Carnegie Institution said the European's analysis of the data represents a "reasonable argument." He said the planet had to form inside the orbit of the larger planet in the system, which orbits the star about twice as far as Earth is from the sun. Boss also points out that Earth is about 18 times as massive as Mercury, so even in our solar system there is a range of possibilities for rocky planets.

Finally, Boss said, the star mu Arae has a higher metal content than the sun, and theory says a planet forming close to such a star can be expected to gather more mass. It's all about how much building material is available, he said.

There are no conventional pictures of the object, as it was detected by noting its gravitational effect on the star. The search project leading to the discovery is led by Michel Mayor of the Geneva Observatory in Switzerland.

While researchers do not know the full range of conditions under which life can survive, the newly discovered world, with its hot surface, is not the sort of place biologists would expect to find life as we know it.

Santos said life on the large world is not likely. But, he added, "one never knows."

I have no doubt that there is life, intelligent life, throughout the universe. In my opinion, the fact that there is life here on earth, proves that there is life in the universe. And since the earth is an average planet orbiting but an average star in our sun - there are probably millions of worlds out there with vibrant life. Our inability to connect with other life is more a function of the size of the universe and our technological primitiveness.

Now what form that life takes is interesting to ponder. There are a variety of atmospheres and temperatures and conditions that would naturally produce different types of life. We might not even recognize the life if we fell over it. In the same way that the life here that lives above ground is fundamentally different than that below water - we could see all manner of life reflective of the conditions around it. In fact, if we didn't know that sea life existed or that there were seas, I venture to suggest that it would be difficult for humans to imagine that life could exist in water.

I sincerely hope I live long enough to see our discovery of life abroad. It's going to be a transformative moment in humanity.

I hope life gets discovered outside of earth as well. Imagine that? And then, imagine it being intelligent.

Keep in mind, the planets they've been able to "find," they don't have the technology to see yet. They can only detect extrasolar planets by the effect their gravitational pull has on the star it orbits. From the "wobble" of the star, they can detect that planets must exist, and how large and far from the sun the planet is. So they really, at this stage, have no way to detect planets that are too small to create a detectable wobble. So truly earth sized planets are impossible to detect under the current technology.

But just you wait, though!

Actually, Vox, I think Hubble has "seen" planets. Unfortunately our esteemed president has signed Hubble's death certificate with no replacement in the queue.

link

Not to mention the fact that his "man on Mars" initiative will end all funding for the current extrasolar efforts.

Has Hubble actually "seen" a planet that actually revolves around a star? The object in the link was some kind of anomaly, it says.

Distant planets, smaller than gas giants, found
Carolyn Y. Johnson The Boston Globe
Wednesday, September 01, 2004


BOSTON American scientists say they have discovered two of the smallest planets ever detected outside our solar system - a sign, they said, that they are on the right track in the quest to find Earth-like planets that could potentially support life.

Until the past few weeks, all of the estimated 130 planets detected in other star systems were believed to be gaseous, Jupiter-sized planets that could not sustain life as we know it. That changed with the discovery last week of a Neptune-sized planet by a European team, and with the news on Tuesday that two similar planets - estimated at 14 to 18 times the size of Earth - had been detected.

The series of findings encouraged astronomers to believe that the techniques they are using are working.

"We're on our way to finding our first exo-solar Earth, and that's an exciting highway to be on," Barbara McArthur of the University of Texas said at a National Aeronautics and Space Administration news conference in Washington on Tuesday.

McArthur led a team that discovered one of the planets. A group from the Carnegie Institution of Washington and the University of California/Berkeley discovered the other. The composition of the planets is unknown, but their mass suggests to the scientists that the new planets may, like Neptune, be a mixture of ice, rock and gas.

The planets could be gaseous giants that have somehow been whittled down: "Gas midgets, or something like that," said Alan Boss, a research astronomer at the Carnegie Institution. He said the more tantalizing and likely option was that these planets were the "tip of the rocky planet iceberg" and were the first examples of a class of solid planets that are either "ice giants" or "super-Earths."

Astronomers are hoping to observe one of the planets in an eclipse, as it crosses between the Earth and its star, which would allow them to measure its dimensions and calculate its density - thereby telling them whether it is solid or gaseous.

In the meantime, "it does make sense to think of these planets differently, just as in our own solar system there is a difference between Jupiter and Saturn and Neptune," said Dave Charbonneau, an astronomer at the Harvard-Smithsonian Center for Astrophysics. The planets "probably aren't just balls of hydrogen and helium. It's possible that they are primarily ice and rock."

The two other, larger, exo-solar planets were discovered by a group led by scientists from the Harvard-Smithsonian center.

While astronomers warn that it may be 10 years before a truly Earth-like planet is discovered, the new finds are part of an encouraging trend.

Detection techniques have not radically changed, but improved telescopes and other instrumentation have finally given astronomers the ability to see smaller planets than before.

The Boston Globe