An article yet again about finding a second Earth outside the Solar System

The articles on finding a second planet similar to Earth just keep coming. Another one just appeared on space.com. As mentioned before, the discovery of one (and more) extrasolar Earth-like planet will be an absolutely epoch-making discovery, because it will change our view of space from that of an immense black void, to that of an immense black void with planets we can set down on, visit and live on, if we can just get all the way to where they are. Now for some interesting parts of the article:

Planet hunters say it's just a matter of time before they lasso Earth's twin, which almost surely is hiding somewhere in our star-studded galaxy.

Momentum is building: Just last week, astronomers announced they had discovered three super-Earths — worlds more massive than ours but small enough to most likely be rocky — orbiting a single star. And dozens of other worlds suspected of having masses in that same range were found around other stars.

"Being able to find three Earth-mass planets around a single star really makes the point that not only may many stars have one Earth, but they may very well have a couple of Earths," said Alan Boss, a planet formation theorist at the Carnegie Institution of Washington in Washington, D.C.

and:

Marcy, Boss and other scientists are optimistic that within the next five or so years headlines will be splashed with news of a near twin of Earth in another star system.

"What is amazing to me is that for thousands of years humans have gazed at the stars, wondering if there might be another Earth out there somewhere," Boss told SPACE.com. "Now we know enough to say that Earth-like planets are indeed orbiting many of those stars, unseen perhaps, but there nevertheless."

Note that people no longer talk about if there are other Earths, just how many. We've found planets larger than Jupiter, the same size as Jupiter, smaller than Jupiter, around the size of Neptune, a few times bigger than Earth, and the next size to come along will be exactly the same size as Earth. Lastly:

Two techniques are now standard for spotting other worlds. Most of the planets noted to date have been discovered using the radial velocity method, in which astronomers look for slight wobbles in a star's motion due to the gravitational tug of an orbiting planet. This favors detection of very massive planets that are very close to their host stars.

With the transit method, astronomers watch for a dimming of light when a planet passes in front of its host star. Though more haphazard, this approach works when telescopes scan the light from hundreds or thousands of stars at once.

Both methods are limited by their ability to block out the overshadowing light of the host star. For instance, the sun is 100 times larger, 300,000 times more massive and up to 10 billion times brighter than Earth. "Detecting Earth in reflected light is like searching for a firefly six feet from a searchlight that is 2,400 miles distant," writes a panel of astronomers recently in their final report of the Exoplanet Task Force.

With upgrades in spectrometers and digital cameras attached to telescopes, astronomers' eyes have become more sensitive to relatively tiny stellar wobbles (measured by changes in certain wavelengths of light) and dips in starlight from ever smaller planets.

The discovery of super-Earths announced last week reflects this technological leap.

"I think why astronomers are really excited [about the super-Earth discovery] is it just shows that technology has really matured and so they're able to see these very subtle wobbles due to these low-mass planets," said David Charbonneau of the Harvard-Smithsonian Center for Astrophysics in Massachusetts. "Those were fairly massive stars. If they were able to get the same precision on a lower-mass star, they would be able to look at even lower-mass planets and so those really would be analogs of the Earth."

The fast track

To eek out even more sensitivity from current technologies, Charbonneau suggests astronomers look for worlds around small stars.

He and other astronomers are in fact probing the universe for transiting planets orbiting M dwarfs, or red dwarfs, which are about 50 percent dimmer than the sun and much less massive. Red dwarfs are also considered the most common star type in the universe.

"I think the real opportunity there is to study low-mass stars, and that's because we're looking for very small planets," Charbonneau said. "The difficulty is the ratio between the planet's mass and the star's mass or the planet's size and the star's size depending on how you want to find it."

The low mass and luminosity means any changes to the star due to an Earth-mass planet are much more likely to be detected.

"A late M star is about 10 times smaller than the sun," said Penn State's James Kasting, who studies planetary atmospheres and the habitable zones of exoplanets. "So Earth going in front of an M star would give a 1 percent signal. That's like Jupiter going in front of the sun." Kasting added, "We could conceivably find an Earth analog planet by this method within the next five or ten years."

Other teams are gearing up to look for Earth-like worlds orbiting massive stars like the sun. NASA's Kepler observatory is scheduled for launch in February 2009, after which the high-powered telescope will monitor about 100,000 stars in the Milky Way looking for periodic dimming of starlight due to a planet's transit in front of the star.

The French COROT mission is already up in space working in a similar fashion.

Ha, one user writes the following in the comments section:

I think this is the 100,000nd time of seen an article such as this. "We are on the verge of finding Earths twin". I don't doubt that. And I don't doubt that it would be an incredible event. However, I'm kinda tired of seeing "clip show" articles. (yeah, I know... then don't read them) Though I supose it does aid those who don't keep up on the subject.

Perhaps, but exciting nevertheless. It's like politics - you can find a few dozen articles and editorials at any one time about each of Obama's and McCain's statements (and about Hillary Clinton before), but that doesn't make the process any less exciting.