The Second Earth !

The search for a second Earth has long enthralled readers of science fiction. What rich and varied life could it contain? What would such a discovery mean for humanity's own place in the Universe? How many similar planets are out there? The question is more than a philosophical puzzle, and it comes with a hard scientific edge that should be considered sooner rather than later. As the search for planets beyond the Solar System widens and public interest in the quest grows, at which point should astronomers declare the hunt for another Earth a success?

Hundreds of candidate planets have been identified, and some have been profiled, if not as a second Earth, then as signs that the search is heading in the right direction. Last month, NASA announced the discovery of the smallest extrasolar planet yet: Kepler-10b, which has 1.4 times the diameter and 4.6 times the mass of Earth, and was discovered by NASA's Kepler spacecraft. Although the planet orbits too close to its star to support life, the news was heralded by some media outlets as a landmark in the search for a new Earth, particularly because Kepler-10b is the first exoplanet with a dense and rocky core.
Attention on Kepler's mission will intensify again this week, as NASA publicly releases a batch of its data. The satellite focuses on a single point in the sky, where it can keep track of some 150,000 stars. Kepler observes the decrease in the brightness of these stars as planets pass in front of, or 'transit', them, and the findings are used to target telescopes on the ground.
It takes three to four such confirmed transits before astronomers are confident that they have found a planet, which makes it too soon to be sure whether Kepler has found a world truly similar to Earth. (By definition, Earth-like planets orbiting a star similar to the Sun pass in front of their stars about once a year, and Kepler has only been in place for about 18 months). All exoplanets confirmed to date orbit much closer to their stars than does Earth; they are too close for conditions to allow the existence of liquid water, which is what defines a star's 'habitable zone'.
As more data are analysed, they will probably produce a string of reports of ever-smaller planets, until we get an Earth-sized example. Many of these small planets are likely to orbit M-dwarfs, by far the most numerous type of star in the Universe. The habitable zone around these stars is very narrow, but Kepler may find a rocky planet there. Would that be the first Earth-like planet? Probably not if, as seems likely, it were to be tidally locked, so that one side faced permanently towards the star.
What about planets that orbit larger stars? Does a first Earth-like planet have to orbit in the habitable zone of a G2-type star, similar to the Sun? If so, must the planet be Earth-sized? And is the focus on a habitable zone defined in terms of liquid water appropriate? As the Universe reveals its secrets, we discover it to be a more diverse and stranger place than we had anticipated. Would it be so odd to conceive of life on a dry or frozen world? Must the first Earth-like planet be capable of supporting life, or human life in particular?
The answers to these questions are important because the public-relations rewards of planet-hunting — and planet-finding — are great. The temptation to hype each discovery is equally large, but so is the scope for confusion and public scorn, especially given the rabid response on some blogs to NASA announcements. Set the bar for 'Earth-like' planets too low, and a string of repeated discoveries could be overwhelming. Set the bar too high, and a planet that meets the strict criteria may not emerge at all. If that were to happen, the Kepler mission would risk being viewed as a failure — which it most certainly is not.
Amid the excitement of exploring a new frontier, astronomers should pause to consider the public reaction to their work. Then they should decide how a standard should be set. Perhaps a reasonable starting point would be to define an Earth-like planet as one of similar size to Earth, orbiting in the habitable zone of any star, and not tidally locked. More important than the details of the definition is that the relevant criteria are established before the claims start to pile up. To announce the discovery of the first Earth-like planet would be a stunning success. To announce it more than once could look like carelessness.

Hunting for Earth-like Alien Planets- Q & A with Astronomer Geoff Marcy

Since astronomers discovered the first planet beyond our own solar system back in 1992, they've been on somewhat of a roll — the tally now tops 500.And the finds are about to ramp up dramatically. NASA's planet-hunting Kepler mission will make much of its data public. A press conference will follow tomorrow, during which researchers are expected to announce intriguing new information about many more possible alien planets.Humanity thus appears poised to enter a productive new era in the study of alien worlds. One man leading the charge is Geoff Marcy, an astronomer at the University of California, Berkeley, and a Kepler co-investigator.
Marcy has had a hand in finding more alien planets than anyone else. He helped spot 70 of the first 100. He also found the first multi-planet system around a sun-like star, and he discovered the first planet that transits — or passes in front of — its star from our perspective on Earth.SPACE.com caught up with Marcy last month in Seattle, at the winter meeting of the American Astronomical Society, to chat about the accelerating pace of planet discovery, what we still don't know about alien worlds and whether there might be intelligent life elsewhere in the universe.
SPACE.com: What has led to the recent explosion in alien planet discoveries? Is it primarily better instrumentation, or better techniques?
Marcy: Well, let me give you a different vantage point. There is a bunch of astronomers who've been working really hard, and they're really innovative, pushing on the frontier technically, pushing on the frontier in terms of the science. And basically burning the midnight oil, essentially literally. I'm giving you the human component of all of this, because sometimes you don't get to see it.
What sometimes gets lost in the shuffle when a nice result shows up on all of the Web pages and the newspapers around the world — what you don't realize is to get that result meant that five or 10 people were burning that midnight oil, trimming the errors down to the point that the Earth-size planets are detectable.
It's easy to dismiss the discoveries as, "Oh, it's new computers, or it's new optics." These things happen because amazing people dream and then put their dreams into perspiration-dripping action.
SPACE.com: So if we were to have this conversation in 20 years, where do you think the total exoplanet count would stand?
Marcy: Honestly, Kepler's so good that it's hard to beat it. It gets the numbers. Kepler's going to find thousands. There's going to be another follow-up to Kepler, either from Europe or the U.S. or both. They'll find thousands. I bet by 2020, there'll be 10,000 planets, and by 2030 there might be another 20,000 or 30,000 more planets.
SPACE.com: Will this discovery arc we're on now continue to go up exponentially, or will it plateau?
Marcy: It'll plateau, because you can't do much better than Kepler. But let's be fair here. It's not the number of planets we care about; it's the quality. We want the Earth-size. We want planets in the habitable zone, and ultimately planets that are sending little radio signals to us for some reason or another.
SPACE.com: You've said that, with exoplanets, theory has really struck out. What are some of the things that we thought we knew, but it turns out were totally wrong about?
Marcy: Well, the first thing — I go back to 1996. No one wants to talk about this, because it's so embarrassing. The reason that as a community we struggled to find the first hot Jupiters isn't because we didn't have the technology. It's because the theorists led us astray. I'm speaking slightly jokingly, but not really.
There were theorists who said, "Look at our solar system. Of course the small, rocky planets are close in. The host star burned off the gases, so you're left with rocky planets. And look at the giant planets like Jupiter and Saturn — they had to form farther out, because it's colder, and the gases can gravitationally stick to the planets. Therefore, all planetary systems will have the following architecture: There will be an inner planet. The second planet out will be named Venus. The third planet out will have great lattes." I mean, it was just silly.
SPACE.com: And that's based on a sample size of one.
Marcy: It would be like trying to characterize human psychology by going to one distant Indonesian island and interviewing one person, and thinking that that gave you the full range of human psychology. And in 1996, there were papers where they said, Jupiter-sized planets, Saturn-sized planets, will all orbit far from their host star. Well, that of course tells you what to look for. If you write a proposal to try to find anything else, you're flying in the face of wisdom. And we know now, of course, how near-sighted that was, how parochial that was.
SPACE.com: So do you think we are starting to get a handle on exoplanets now?
Marcy: I think so. We're always a little too confident, so I would hate to say, "Go home, we're all done." We do have these planets we're finding with Doppler work, and now with Kepler, that are five times the size of Earth, three times the size of Earth, 1.4 times the size of the Earth. And I don't think we really know how they formed.
Even the one we announced [the rocky, nearly Earth-size Kepler-10b], there are two main ways it might've formed. It might've formed like the Earth, or it might have formed like Uranus but it got so close to the host star that the gases and the water got evaporated away and left a bare, rocky core remnant.
SPACE.com: What are some of the biggest mysteries that are left?
Marcy: There's one huge one that nobody really wants to talk about. It's the age-old question: Are Earth-like planets common? We know they're out there for sure. I mean, there's too many stars. But there's two parts to the question. What do you mean by "Earth-like?" And then, how common are they?
Basically, we know what we want for Earth-like, so we shouldn't beat around the bush: We would love to know whether there are planets suitable for life as we know it.
And those Earth-like properties are a little bit mysterious, but we have some ideas. You want water in liquid form, you want stable temperatures over the course of millions, preferably billions, of years so that Darwinian evolution can get a good toehold.
You probably want a moon to stabilize the spin axis. You probably want a Jupiter to sweep up the debris. You probably want a stable ocean for a long enough time that it can serve as the solvent for biochemistry.
So that's probably what we mean by "Earth-like." But how common they are, we just don't know.
SPACE.com: Your research suggests that smaller planets may be pretty common — that nearly one in four nearby sun-like stars could host a roughly Earth-size planet.
Marcy: Yeah. But here's the sleeper idea that no one wants to talk about: Because Earth-size planets are so much smaller than the Jupiters, Saturns, Uranuses and Neptunes, and we now know that planets often get thrust into eccentric and misaligned orbits, the Earths are like the Volkswagens on a highway full of 18-wheelers.
The vulnerable planets are the small ones. And so to the extent that planetary systems undergo a billiards era — the Earth would be like putting a small marble on a pool table of 15 billiard balls. As you break, the little planets are going to be the ones slingshot right out of the solar system pool table.
SPACE.com: It's one thing to say they can form. But to say that they'll actually stick around long enough — that's a totally different question.
Marcy: Yeah. And I think they'll form. It's hard to imagine they wouldn't. If you make Jupiters, why wouldn't you make Earth-size planets? But the Earths — and maybe the Volkswagen is giving it too much credit. It's an 18-wheeler and a tricycle. Earth is a tricycle on Highway 5 running up and down the Pacific Coast.
And you don't even have to hit the tricycle. You just have to come close enough that gravity slingshots the poor tricycle right out of the system. So it's possible that Earth-like planets form, they get thrown out into the cold darkness of the galaxy and they have no chance of starting — never mind sustaining — life, because it's too cold out there. And that's possible. We might be rare.
And by the way: Where are the SETI [search for extraterrestrial intelligence] signals? There is a non-detection that's like the elephant in the room. Forty years of Frank Drake and Carl Sagan looking for SETI signals, and we have precisely zero to show for it. So there's an indication — not definitive — that maybe the Earth is more precious than we had thought.
SPACE.com: Our solar system is so young, compared to the universe. And the universe is so big. So there's been lots of time and opportunity for advanced civilizations to get started, and to try to contact us. Some people think that the fact that we seemingly haven't been contacted means that we may well be alone in the universe.
Marcy: Well, you have to fold it in. The absence of an intelligent radio or television wave from any advanced civilization represents one indication, not a proof, that maybe habitable planets that sustain Darwinian evolution for a billion years —maybe they're rare. Maybe.
SPACE.com: What do you reckon? Do you have a gut feeling about this?
Marcy: I do. If I had to bet — and this is now beyond science — I would say that intelligent, technological critters are rare in the Milky Way galaxy. The evidence mounts. We Homo sapiens didn't arise until some quirk of environment on the East African savannah — so quirky that the hominid paleontologists still can't tell us why the australopithecines somehow evolved big brains and had dexterity that could play piano concertos, and things that make no real honest sense in terms of Darwinian evolution.
Why the high chaparral on the East African savannah would've led to a Tchaikovsky piano concerto, never mind the ability to build rocket ships — there's no evolutionary driver that the australopithecines suffered from that leads to rocket ships. And so that — and the fact that we had to wait four billion years without humans. Four billion years?
SPACE.com: Yes, it took four billion years to get there.
Marcy: Since the Cambrian explosion, we had hundreds of millions of years of multi-cellular, advanced life in which, guess what happened with brain size? Nothing.
You know the greatest species ever to roam the Earth? The dinosaurs — every kid knows this. And why? Well, because for 100 million years, the dinosaurs roamed the Earth. There were big ones, there were small ones. Every generation of baby dinosaurs had to outcompete all of the other dinosaurs. And you would think after 100 million years, each generation of baby dinosaur that was a little smarter would have out-survived the others and thereby slowly but surely increased dinosaur cranial size.
The reality from the paleontological record? Dinosaurs had the brains of chickens, and never got bigger. It shows that braininess is not a primary driver in evolution. We humans came across braininess because of something weird that happened on the East African savannah. And we can't imagine whether that's a common or rare thing.
SPACE.com: People assume evolution is directed, and it's always leading toward higher complexity and greater intelligence, but it's not.
Marcy: It's not. Dinosaurs show this in spades.
SPACE.com: You've said that we're about to enter a golden age of direct exoplanet imaging. Is that what the future holds — getting good, direct looks at alien planets to try to gauge their potential to support life?
Marcy: It is. There's two great things that we should be doing. One is that we should, as a species — and this means ESA [the European Space Agency], Japan, China, India, the United States, Canada — work together internationally to fund a space-borne telescope, probably interferometric, that can take pictures of Earth-size and Earth-like planets. We know how to do it.
Yes, it'll be expensive, but we do expensive things in science, and this is a great quest for humanity: Are there Earth-like and, indeed, habitable planets out there? But the other thing to do — we should say it right away. We should have a full-fledged, Apollo-like SETI search. Why haven't we coherently gathered our resources and done SETI right?
SPACE.com: Finding alien intelligent life would be such a huge deal. It would change the way we think about ourselves and our place in the universe.
Marcy: Exactly. So why aren't we putting together our resources, nationally and internationally, and constructing a major radio telescope facility — and maybe, if there's money left over, an infrared facility — and sampling the universe for signals?
We know what to look for. That would be the rat-a-tat-tat of a radio signal. We don't know exactly what the code would be, but we'd be looking for pulses in the radio, in the infrared maybe, in the X-ray or UV. We'd have to think broadly. But this is a great quest for humanity.
It's the Armstrong, it's the Columbus of our time, essentially reaching out with radio waves and hunting for alien intelligent life. It would be a marvelous, inspirational effort. And right now we don't have enough going on, in my opinion.
Because it would mean — all 7 billion people on planet Earth would get up in the morning wondering, "Did they find the signal last night?"
SPACE.com: It makes you wonder why nations haven't joined together to do something like this. Economically, it would be a drop in the bucket.
Marcy: It's a drop in the bucket. Frankly, $1 billion would be good. It sounds like $1 billion is a lot of money. But not really. NASA's budget is $19 billion. Nineteen billion dollars every single year. So how about a billion of that for a SETI search? How about one year — 5 percent — to do SETI in a historic, Apollo-like way? I mean, Wow!
It puts Armstrong and the invention of fire sort of on a par. So it's worth one-nineteenth of one year's NASA budget. I think it's a great idea, and we know how to do it.
Yeah, it's a luxury. We need to feed the people on the planet Earth, we need to provide health care, we need to provide better education, we need to make sure that human beings are living. But we're doing that. And a billion is really a teeny fraction of many countries' annual budget.

Courtesy - space.com

Good News from Keplar

Sitting for an interview in his office at the Harvard-Smithsonian Center for Astrophysics (CFA) in Cambridge, Massachusetts, the normally voluble astronomer Dimitar Sasselov looks nervous. Asked for his favourite among the many potential planets discovered by NASA's Kepler planet-finding mission, for which he is a co-investigator, he hesitates, then sidesteps the question entirely. "Personally, I'm already beyond that point. It's not one. It's not a single planet. It's a whole family."
NASA’s Kepler mission has discovered its first Earth-size planet candidates and its first candidates in the habitable zone, a region where liquid water could exist on a planet's surface. Five of the potential planets are near Earth-size and orbit in the habitable zone of smaller, cooler stars than our sun. Candidates require follow-up observations to verify they are actual planets. Kepler also found six confirmed planets orbiting a sun-like star, Kepler-11. This is the largest group of transiting planets orbiting a single star yet discovered outside our solar system.
Most of the Kepler scientists continue to be cautious. By watching the light from some 150,000 stars for the dimming that could signal a planet crossing in front of them, Kepler is extraordinarily efficient at finding possible planets. But Kepler has yet to find another Earth — a small, rocky planet with an orbit of a few hundred days and well inside the habitable zone in which water can exist and life can arise. That is for a fundamental reason; the blips that Kepler detects show only the radius, and not the mass, of an observed planet, which means that the density and composition generally remain unknown.
"In one generation we have gone from extraterrestrial planets being a mainstay of science fiction, to the present, where Kepler has helped turn science fiction into today's reality," said NASA Administrator Charles Bolden. "These discoveries underscore the importance of NASA's science missions, which consistently increase understanding of our place in the cosmos."
The discoveries are part of several hundred new planet candidates identified in new Kepler mission science data, released on Tuesday, Feb. 1. The findings increase the number of planet candidates identified by Kepler to-date to 1,235. Of these, 68 are approximately Earth-size; 288 are super-Earth-size; 662 are Neptune-size; 165 are the size of Jupiter and 19 are larger than Jupiter.
Of the 54 new planet candidates found in the habitable zone, five are near Earth-sized. The remaining 49 habitable zone candidates range from super-Earth size - up to twice the size of Earth - to larger than Jupiter.
The findings are based on the results of observations conducted May 12 to Sept. 17, 2009, of more than 156,000 stars in Kepler's field of view, which covers approximately one four-hundredth of the sky.
"The fact that we've found so many planet candidates in such a tiny fraction of the sky suggests there are countless planets orbiting sun-like stars in our galaxy," said William Borucki of NASA's Ames Research Center in Moffett Field, Calif., the mission's science principal investigator.
"We went from zero to 68 Earth-sized planet candidates and zero to 54 candidates in the habitable zone, some of which could have moons with liquid water." Among the stars with planetary candidates, 170 show evidence of multiple planetary candidates. Kepler-11, located approximately 2,000 light years from Earth, is the most tightly packed planetary system yet discovered.
All six of its confirmed planets have orbits smaller than Venus, and five of the six have orbits smaller than Mercury's. The only other star with more than one confirmed transiting planet is Kepler-9, which has three. The Kepler-11 findings will be published in the Feb. 3 issue of the journal Nature.
"Kepler-11 is a remarkable system whose architecture and dynamics provide clues about its formation," said Jack Lissauer, a planetary scientist and Kepler science team member at Ames.
"These six planets are mixtures of rock and gases, possibly including water. The rocky material accounts for most of the planets' mass, while the gas takes up most of their volume. By measuring the sizes and masses of the five inner planets, we determined they are among the lowest-mass confirmed planets beyond our solar system."
All of the planets orbiting Kepler-11 are larger than Earth, with the largest ones being comparable in size to Uranus and Neptune. The innermost planet, Kepler-11b, is 10 times closer to its star than Earth is to the sun.
Moving outward, the other planets are Kepler-11c, Kepler-11d, Kepler-11e, Kepler-11f, and the outermost planet, Kepler-11g, which is half as far from its star as Earth is from the sun.
The planets Kepler-11d, Kepler-11e and Kepler-11f have a significant amount of light gas, which indicates that they formed within a few million years of the system's formation.
"The historic milestones Kepler makes with each new discovery will determine the course of every exoplanet mission to follow," said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington.
Kepler, a space telescope, looks for planet signatures by measuring tiny decreases in the brightness of stars caused by planets crossing in front of them. This is known as a transit. Since transits of planets in the habitable zone of sun-like stars occur about once a year and require three transits for verification, it is expected to take three years to locate and verify Earth-size planets orbiting sun-like stars.
The Kepler science team uses ground-based telescopes and NASA's Spitzer Space Telescope to review observations on planetary candidates and other objects of interest the spacecraft finds. The star field that Kepler observes in the constellations Cygnus and Lyra can only be seen from ground-based observatories in spring through early fall. The data from these other observations help determine which candidates can be validated as planets.

Q-A About Habitable Planet Gliese 581g

A newfound Earth-sized planet discovered in the habitable zone of a nearby star looks very promising for the possibility of extraterrestrial life, but many unknowns remain. The planet, Gliese 581g, is one of two new worlds discovered orbiting the red dwarf star Gliese 581, which now has a family of planets that totals six. [Tour the six Gliese 581 Planets] . Here is Starry Messenger's look at what scientists know so far about the intriguing world, as well as a few questions that don't quite have answers yet. Consider it a new entry into Earth's own hitchhiker's guide to the galaxy -

How do I say the planet's name?
 
Gliese 581g may look like it should rhyme with "Grease," but it is actually pronounced as two-syllables as (Glee-zuh). The name comes from the German astronomer Wilhelm Gliese, who catalogued the planet's parent star Gleise 581 as part of a star survey first published in 1957.

Where is Gliese 581g?

The planet Gliese 581g orbits the red dwarf star Gliese 581, which sits 20 light-years from Earth in the constellation Libra. One light-year is about 6 trillion miles (10 trillion km).


How far is it from the parent star?

Early estimates suggest Gliese 581g is 0.15 astronomical units from its star. One astronomical unit is the average distance between the Earth and sun, which is approximately 93 million miles (150 million km). That distance means the planet is close enough to its star so that it can complete an orbit in a little less than 37 days. One of its sibling planets was closer to the hot edge of the habitable zone around the star Gliese 581, and one was farther out the colder edge of the habitable zone. Gliese 581g is located just right between the two.

What is a habitable zone?


Think of a star's habitable zone as the swath of space surrounding a star where conditions for life as we know it are possible. Closer in, a planet roasts. Farther out, it freezes. Planets within that habitable zone, also known as the Goldilocks zone, have a range of surface temperatures that allow for readily available liquid water and other conditions that may support the rise of life. This cosmic sweet spot can vary, because it depends upon the type of star and the point in time for any given star's lifespan.
For instance, our sun's current habitable zone is farther out than that of the star Gliese 581, a red dwarf about 50 times dimmer than our sun. The cooler red dwarf allows the Gliese 581 planets to orbit much closer and still remain in the habitable zone.
A planet within the habitable zone does not have a guaranteed chance of originating life, because biology also depends upon the planet's size and a host of conditions, including chemical makeup. But what little researchers know about Gliese 581g makes it a highly promising candidate.

How big is Gliese 581g in relation to Earth?


The planet is lumped into the "nearly Earth-sized" category. It is between three and four times the mass of our Earth — bigger, but small enough to be rocky rather than gaseous. Its radius is anywhere between 1.3 and two times the size of Earth.

How much would I weigh on Gliese 581g?

An Earth-sized planet with three times the mass of our planet would pull down on your body with three times the force of Earth's standard gravity. That means if you weighed 120 pounds on Earth, you would weigh about 120 x 3 pounds on an Earth-sized planet with three times the mass, or 360 pounds.
But Gliese 581g also has a somewhat larger radius, so that also factors into the equation. A 120 pound person would weigh about 213 pounds on Gliese 581g at the lower end of the size and mass estimates. This all remains theoretical until astronomers can pin down the actual size and mass.

What's it like on the surface?

There is no solid evidence at the moment that suggests what surface conditions might be like, or even if liquid water and an atmosphere are actually present.What researchers know is that the planet exists at the right distance from its star to have liquid water. It's also at the right distance to have an atmosphere which can protect that water, if exists on the surface.
But one of the planet's discoverers, astronomer Steven Vogt of the University of California, Santa Cruz, pointed out that "it's pretty hard to imagine that water wouldn't be there." He likened it to the examples of the Earth, its moon, Mars, and the moons of Jupiter and Saturn. He also noted that the Orion Nebula is making enough water every 24 seconds to fill all the oceans of the Earth. Researchers also know that the planet is tidally locked to its star. That means one side experiences eternal daylight, and the other side experiences unending darkness. Such a locked configuration helps to stabilize the planet's surface climate, Vogt said.
3-D global circulation models have shown that the temperature differences on the day and night sides of the planet would not be enough for water to either freeze or boil off. They also suggest that the atmospheric circulation and wind patterns would be relatively benign.

Does it have moons?

There's one called Pandora...just kidding! There's no info on any moons around Gliese 581g, or around any other planets in its solar system yet. But astronomers have long assumed that alien planets could have moons, and that some of the moons might harbor life.


How long would it take to get there?

This question depends upon how fast you travel. Given our current lack of Star Trek's warp drives, any interstellar expedition would have to travel far slower than the speed of light.A spaceship traveling at a one-tenth of the speed of light would reach Gliese 581g within about 220 years, Vogt said. That would allow the spaceship to begin getting close-up pictures and a sense of the planet's atmosphere.That time scale is not promising for existing human lifespans, but robotic explorers could more easily take up the challenge. However, the fastest spaceships built so far don't come anywhere near even that one-tenth light-speed mark.

What kind of life would we expect to find?

Any discussion about alien life on Gliese 581g is purely speculative at this point, according to co-discoverer Paul Butler of the Carnegie Institution of Washington, in Washington, D.C. Butler took a more cautionary approach as opposed to Vogt, who said his gut feeling told him "the chances of life on this planet are 100 percent." Still, even Butler noted that anywhere you find water on Earth, you find life. He suggested that a similar condition should hold for almost anywhere in the universe, including Gliese 581g if it does hold water.


Why doesn't the planet have a real name?

The planet is called Gliese 581g because its star, Gliese 581, is designated "a," and the four previously discovered planets in the system are called b, c, d and e. But Vogt said that he has unofficially begun calling the planet "Zarmina's World," in honor of his wife.

What would aliens living on Gliese 581 see if they looked toward our sun?

You remember that we don't have evidence of alien life on the planet yet, right? But assuming they exist, aliens could spot our own sun as star in their sky without requiring any telescopes or binoculars. If the alien astronomers had our current level of technology, they would be also able to easily detect Neptune, and possibly Jupiter and Saturn.

32 NEW PLANETS DISCOVERED

Astronomers have found 32 new planets outside our solar system with the High Accuracy Radial Velocity Planet Searcher, better known as HARPS, the spectrograph for the European Southern Observatory's (ESO) 3.6-metre telescope. The number of known exoplanets is now at 406, and HARPS itself has discovered more than 75 exoplanets in 30 different planetary systems. Included in this most recent batch are several low-mass planets – so-called "Super Earths" about the size of Neptune. The image above is an artist's impression of a planet discovered that is 6 times the mass of Earth, which circles the low-mass host star, Gliese 667 C, at a distance equal to only 1/20th of the Earth-Sun distance. Two other planets were discovered previously around this star.
"HARPS is a unique, extremely high precision instrument that is ideal for discovering alien worlds," said ESO astronomer Stéphane Udry. "We have now completed our initial five-year program, which has succeeded well beyond our expectations."No Earth-like planets were discovered in this group that was announced at an exoplanet conference in Portugal.