Are We On the Brink of Finding a Second Earth? NASA/Harvard Teams Say "It Could Happen Anytime Now"

"It could happen almost any time now. We now have the technological capability to identify Earth-like planets around the smallest stars."

David Latham -Harvard-Smithsonian Center for Astrophysics

To date, Planet hunters have spotted more than 200 planets beyond our solar system, but the vast majority are hot, Jupiter-sized planets that would dwarf the Earth and are almost certainly lifeless.

Astronomers may be on the brink of discovering a second Earth-like planet, a find that would add fresh impetus to the search for extraterrestrial life, according to the US journal Science. Astronomers from six major centers, including NASA, Harvard and the University of Colorado, outline how advances in technology suggest scientists are on the verge of being able to detect the presence of small, rocky planets, much like our own, around distant stars for the first time. The planets are considered the most likely habitats for extraterrestrial life.

One technique relies on observing the shift in light coming from a star as a planet swings around it. Until recently, this "radial velocity" method has only been sensitive enough to pick up planets far more massive than Earth, but improvements now make the discovery of a second Earth highly likely, said Dave Latham, a co-author on the paper at the Harvard-Smithsonian Center for Astrophysics.

"It could happen almost any time now. We have the technological capability to identify Earth-like planets around the smallest stars even now," he said.

Earlier this year, the world's largest and most prolific team of planet hunters, the Anglo-Australian, California and Carnegie Planet Searches ( AAPS), reported their findings of 37 exoplanets that have been discovered over the past couple of years, 7 of which were previously unreported brown dwarfs.

Depending on whose number you go by, the total number of exoplanets currently discovered is 212 or 240, the majority of which have been discovered by the AAPS and their colleagues in the California and Carnegie searches.

The method of discovery primarily implemented is studying the Doppler wobble of stars. As a planet orbits its parent star, its gravitational pull causes the star to wobble. Using the Doppler Effect, the scientists are able to determine the velocity of the planet. When the planet moves away from Earth, its star moves toward the Earth, causing it to emit shorter wavelengths, which appear bluer. The opposite is true as well; as a planet moves closer to Earth, its star moves further away, emitting longer (redder) wavelengths of light. The AAPS uses highly advanced, sensitive spectographs to record these very small wavelengths.

But there are things that Doppler searches cannot tell researchers. With Doppler readings, they are able to calculate the velocities of the planets being studied as they move towards and away from the Earth. What Doppler readings are unable tell researchers are the angles of inclination of the orbital planet to the line of sight. This is important information because by being able to calculate the angles of inclination of the orbiting planet, scientists are able to determine the actual physical size of the planet.

The AAPS has developed a technique to find the angle of inclination: transit searches. Transit searches are a relatively new technique which has only just begun giving them results within the past few years. As a planet transits in front of its parent star, passing our line of sight from Earth, scientists are able to calculate its angle of inclination, thereby determining its eccentricity (how elliptical or round its orbital path is). In the years to come, the method of transit searches should advance, resulting in more information about already discovered planets.

Although the next generation of techniques such as interferometric astrometry and direct imaging will be the most promising new methods of detection in the future study and discovery of extrasolar planets, as Chris Tinney of AAPS explains, the most successful and powerful form of study currently in use is complementing Doppler searches with transit searches. By doing so, “You can essentially know everything you can know about a planet. You know exactly its mass and its radius, which means you can work out its density,” and therefore, “you can make estimates as to whether it’s a gas giant or an ice giant planet, or whether it’s rocky.”

As these techniques develop, the smaller and smaller the extrasolar planets being discovered will become.

So when does Tinney expect an Earth-sized planet discovery, now that they’ve gotten down to Venus-sized planets when once they only found those with a mass that of Jupiter’s?

Tinney thinks that “finding a planet of Earth mass is probably a only couple of years away. But…”—and he emphasizes the “but,” pausing for a moment—“there’s always a ‘but.’” As he explains, all of the things they are finding of very low mass are moving in very short orbital periods, which means that they are orbiting close to their parent stars. So although there they are like Earth in terms of their mass and size, these planets are very unlike the Earth in terms of their orbit.

“To find an Earth-mass planet in an Earth-like orbit is just not going to happen with the Doppler technique,” Tinney states. It is simply beyond the technology currently developed. Essentially, it would mean that they would need to be performing measurements 100 times better than any technology is capable of doing.

So does this rule out the possibility of finding a habitable planet?

Not quite. There is a “trick” to planet hunting. Scientists can look for Earth-mass planets in short period orbits around lower mass stars. These types of stars are called M dwarfs and have a mass one tenth the size of the Sun, which means that the velocity signal is ten times larger, and therefore the radius at which the planet must be from the star in order to have water or liquid on its surface is much smaller. For now, it’s Tinney’s opinion that some of the recent reports about habitable planets being discovered “is more hype than reality,” but that the discovery of such planets “will come in due course.”

In fact, that’s precisely what Tinney is currently working on, aside from his AAPS commitment. He has convinced the Gemini Observatory—a collaboration of the US, Canada, UK, Australia, Brazil, and Argentina—to build a spectrograph on one of its largest class of telescopes. In order to perform the types of studies needed to find other Earth-mass planets, scientists would need to being studying the near infrared, rather than the green wavelengths of visible light. This new Gemini spectrograph, called the Precision Radial Velocity Spectrometer, will specifically be designed to do very high precision Doppler work in the near infrared, rather than the optical. Once that type of technology is developed, Tinney believes that rather than finding the occasional one or two Earth-sized planets around M dwarf stars, finding more and more “will be much more straightforward,” thereby dispelling some of the current hype and allowing scientists to gather actual statistics about these types of systems.

NASA's mantra of "follow the water" has defined the search for extraterrestrial life on and other planets. If water is crucial for life, then the most likely sanctuaries will be planets which lie in a "habitable zone" just the right distance from a star, so that it is neither so hot that water evaporates, or so cold that it remains permanently frozen.

Dr Latham of the Harvard-Smithsonian Center said missions such as Nasa's Kepler space observatory, which launched in early March, would have a high chance of finding Earth-like planets if they are out there.

"These are the biggest questions. Are there habitable abodes? Are we alone?" he said. "Put it like this. If we don't find anything, I'll have to rethink my agnosticism."

Posted by Casey Kazan. Image Credit: Corbis.

Related Galaxy posts:

Lonely Hearts of the Cosmos Revisited -NASA's Phoenix Probe & the Search for Extraterrestrial Life
SETI's Search for ET Goes Exponential
Cruising the Goldilocks Zone -The Search for "Super-Earths"
Non-Carbon Lifeforms -Why We May Overlook
The Milky Way Enigma -How Galactic Forces May Control Life on Earth
 Earth's Twin Habitable?
Search for Extraterrestrial Genomes

Story Link:

http://www.guardian.co.uk/science/2007/oct/12/spaceexploration?gusrc=rss&feed=science

Comments

[clownfish]

The smallest exo-planet currently listed on NASA's Planet Quest website weighs in at 3.3 earth masses, the host star is MOA-2007-BLG-l, about 1000ly away. You have, apparently, made an error in your story with the paragraph, "So when does Tinney expect an Earth-sized planet discovery, now that they’ve gotten down to Venus-sized planets when once they only found those with a mass that of Jupiter’s?" Venus is actually slightly smaller than Earth, by some 650km.

[EvilCosmicMonkey From Knoxville]

Looking for " Second Earths " is very good, but the chances of life exactly as we know it developing / evolving / being created there has got to be extremely slim. IF we go to such a planet someday, we ain't gonna find a Grand Canyon, Mt. Fujiyama, Mt. Everest, etc., & we very likely aren't going to find humans or humanoid beings there.

And one shouldn't completely write off the Jupiter - type planets as TOTALLY lifeless. IF we find a life - form or several in the clouds of Jupiter or Saturn, they might exist on Jovian - type planets around other stars.

[Dennis Nilsson]

We haven't yet found all life on our own homeplanet, planet Earth!

All this strange "UFO"-objects seen now under several decades could be a unknown life in Earth clouds!

Austrian scientists discovered 2002 a bacteria living and reproducing within clouds on Earth.

“Does anything live in clouds?”
http://www.earthsky.org/teachers/article/life-in-clouds

http://www.solarviews.com/eng/cloud1.htm

[Lemdog]

My money is on finding life (or at least the signs of it) on a planet light years away far before we find it on Europa or Mars or the clouds of Jupier.

[EvilCosmicMonkey From Knoxville]

We should look here 1st, just because it's closer. We don't need to climb Mt. Everest until we conquer the big mound of earth in or near our yard. Mars, Europa, Titan, my money's still on finding something there 1st, at least FOSSILS on Mars, if nothing else, or primitive multicellar critters on Titan or Europa. Then we make like Marco Polo.

[lane]

"Put it like this. If we don't find anything, I'll have to rethink my agnosticism."

really?

[Pessimist]

Somewhere else for us to mess up before we get this planet right.

[Saudi]

We are failing to manage our mother earth resources and even are spoiling them, instead of focusing our attentions to take care of our planet and work on solutions, we want to find another one! unreachable anyway.

http://www.saudisolutions.org/

[Jimmy MAch]

Oh yeah, make no doubt about it, it WILL happen. Just a matter of time.

RT
www.Privacy-Center.net

[Kevin]

They may find a planet with similar dimensions to earth, and it may even support simple life, but these articles, or their headlines, are misleading. They suggest that we'll find a planet with complex, intelligent life, and folks, that just ain't going to happen, at least not anytime soon. All the required coincidences and happenings required for simple cellular life to form complex, multicellular, even intelligent life makes it EXTREMELY unlikely we'll ever find such a scenario other than ourselves. If such a scenario exists out there, it's bound to be so rare, so few and far-in between, that we won't bump into them anytime in the near term. Though I could be wrong, I wouldn't bet against my suggestion.

[Jaybird2005]

We will find the 'habitable' planet just about the time interest starts to fade on searching for it or funding almost runs out. Then we can start paying for a huge project to get us there (which will be impossible but will still cost 10s of millions), with no definitive results. Science seems to be out of the business of answering questions and into the business of performing experiments that ask even more questions.

[Televisoin Spy]

I certainly hope so, we're just about trashed this one.

[Roger Smithers]

It's amazing how ironic this is, given that The Disclosure Project in 2001 gave the National Press Club's most watched webcast (over a billion people round the world have now seen it) where some of the over 500 official-level witnesses gave testimony (and promised to do so under oath before Congress) about ET interaction with this planet and it's governments.

These were not kooks - they were people in charge of our nuclear weapons, senior politicians, FAA flight controllers, military personnel, intelligence insiders - ALL with VERIFIED credentials who stated plainly and clearly of numerous cases where they had interacted directly or indirectly with either ETs themselves, in an official capacity, on this planet, or where they had knowledge of insider black programs dealing with ET liaison, ET technology, or technology we built based on ET technology.

This may sound utterly outrageous, but the fact of the matter is - these were totally solid, reliable witnesses, who have proven themselves in various critical professional capacities.

You can NOT deny the evidence of the Disclosure Project. Check youtube for the videos.

http://www.disclosureproject.org

[freddy]

Oh yeah, make no doubt about it, it WILL happen. Just a matter of time.

[Frank Glover]

"We are failing to manage our mother earth resources and even are spoiling them, instead of focusing our attentions to take care of our planet and work on solutions, we want to find another one! unreachable anyway."

Um, we can do both, and 'reachability' isn't the point. (MOST of the Universe is currently unreachable.) It's not as if one somehow takes away from the other. Money isn't *that* tight, and ours is clearly a civilization that can walk and chew gim at the same time...

"We should look here 1st, just because it's closer."

See above.

"They may find a planet with similar dimensions to earth, and it may even support simple life, but these articles, or their headlines, are misleading. They suggest that we'll find a planet with complex, intelligent life, and folks, that just ain't going to happen, at least not anytime soon. All the required coincidences and happenings required for simple cellular life to form complex, multicellular, even intelligent life makes it EXTREMELY unlikely we'll ever find such a scenario other than ourselves."

The laws of physics and chemistry are the same everywhere. The point isn't whether or not it's just like us (though the differences will still tell us something), but whether *any* life at any degree of complexity can be out there, evolving and playing out in its own way.

In any case, the only way to know, is too look. Unless Roger is right after all, the Universe seems not interested in effortlessly delivering the answers to us on its own.

[Des]

Frank Glover is right about physics and chemistry. All life is a chemical reaction and physics determines viability. The physics of life's conception are not the same for life's development after conception has initiated life.

We are used to thinking of our solar system as four "rocky" inner small planets and four giant, gaseous planets along with a lot of comets and asteroids, etc. We tend to forget that our planet, Terra, does not resemble the other three inner globes as it has a very, very large satellite (likely acquired long after actual formation of the planet itself), a strong
magnetic field, a massive metal (iron) core, a large volume of H2O which exists only here in its three physical forms simultaneously, a lithosphere composed of many elements, and a few other peculiarities.

The physics of those characteristics act upon the chemistry of life, and the end product is us. Minor variations in the physical realm would have precluded our development. Other solar systems may have the conditions necessary for life support, but not necessarily life conception. There are not likely other lifeforms wandering around the universe.

[Big Robby]

If there isn't any intelligent life out there, it seems like an awful waste of space. Yes, I said it.

[güvercin]

http://guvercin-forum2009.yetkinforum.com

[video]

very nice thanks

[brk]

http://koxpcu.yetkin-forum.com

http://guvercin-forum2009.yetkin-forum.com