A CLOSE-KNIT GROUP: An artist's impression of the densely packed Kepler 11 system shows three planets transiting in front of their host star simultaneously.
Image: NASA/Ames/JPL-Caltech/T. Pyle
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Thirty million kilometers away, trailing the pale blue dot that is Earth as it orbits the sun, is a spacecraft designed to find some of the countless other pale blue dots that may speckle the galaxy. NASA launched this spacecraft, known as Kepler, in 2009 to take a census of Earth-like planets in the hopes of figuring out how common—or how rare—are the conditions under which life has thrived here.
Just over halfway into that 3.5-year campaign, Kepler has not been on the job long enough to conclusively identify any habitable worlds, but its discoveries are growing ever more tantalizing. In a field where small is good—small meaning less like Jupiter and more like Earth—the latest batch of planets netted by the space observatory includes five of the eight smallest worlds now known outside the solar system. All five of the new extrasolar planets, or exoplanets, as well as one more world whose properties are not yet fully understood, orbit a sunlike star called Kepler 11, some 2,000 light-years away. A group of researchers announced the discovery of the six-planet Kepler 11 system in the February 3 issue of Nature. (Scientific American is part of Nature Publishing Group.)
Almost simultaneously, the Kepler team was preparing a list of more than 1,200 additional objects the spacecraft has located that may also be planets. "We have a huge number of candidates," says Kepler's principal investigator, Bill Borucki of NASA Ames Research Center, Moffett Field, Calif. "It's very exhilarating," says Borucki, who first put forth the idea for Kepler in 1984 and proposed the concept several times before getting NASA's approval and funding. The data on the numerous candidates are somewhat preliminary and require validation, but a new analysis by a pair of astrophysicists at the California Institute of Technology suggests that the percentage of false positives among Kepler's candidate planets may be less than 10 percent.
If that is the case, then Kepler is well on its way to vastly augmenting the roster of known exoplanets, of which there are now 500 or so, and may have already gotten a whiff of several potentially habitable worlds. "We have 54 planets in the habitable zone of their stars," Borucki says, referring to the temperate orbital zone around a star that would allow for the existence of liquid water on a planet. "One of them is 0.9 times the radius of the Earth, and four of them are less than two Earth radii." Any of those would be the most Earth-like world ever detected outside the solar system. What is more, some of the larger, more Jupiter-like planets Kepler is sniffing at in the habitable zone might have moons, and some of those satellites would themselves be potentially habitable. "It's sort of awesome," Borucki says of Kepler's haul. "The implications are that there are an awful lot of planets out there."
For now, those 1,200-plus objects remain mere candidates requiring follow-up and confirmation. Until then the six planets around Kepler 11, which have been validated by various means, are the "Kepler spacecraft's latest—and we think its greatest—finding to date," said mission co-investigator Jack Lissauer of Ames during a January 31 teleconference with reporters. The Kepler 11 system is unique for several reasons: For starters, it is among the largest collections of worlds known outside our own solar system, and all six of the planets Kepler has found there are aligned so that their orbits carry them across the face of their host star from Kepler's vantage point.
Kepler continuously tracks more than 150,000 stars; when a planet passes in front of one of them, in a kind of mini eclipse known as a transit, the spacecraft registers a slight dip in the star's apparent brightness. Transits, though subtle and brief, carry a great deal of information about a planet: the amount of dimming conveys the diameter of the planet, and the frequency of transits provides the planet's orbital parameters. But such fortuitously aligned planets are relatively rare; aside from Kepler 11, only one star is known to host more than one transiting planet. A planetary system has to be almost perfectly planar for multiple planets to transit—Lissauer compared the astonishing flatness of the Kepler 11 system to a scaled-up vinyl LP.
What is more, the planets of the Kepler 11 system are so densely packed that all six would fit within the orbit of Venus, the second-closest planet to our own sun. (All of the newfound worlds are too close to their star and thus too hot to be plausibly habitable.) That is by far the densest planetary configuration known, Lissauer said. In fact, the five innermost worlds around Kepler 11 are so close together that gravitational interactions among them produce measurable perturbing effects on their individual orbits, allowing the researchers to make estimates of each planet's mass. The sixth, outermost planet is too far from any neighbors to exert such effects, so the Kepler scientists can only set an extreme upper limit on its mass.
Among the five worlds whose properties are well understood, relative to Earth the planets range from 2.3 times to 13.5 times its mass, and from about two times to 4.5 times its diameter. A few other planets are known to be smaller, but the initial estimates peg two of the bodies orbiting Kepler 11 as the lowest-mass worlds for which a complete set of planetary information—mass, diameter and orbit—has been obtained.
Borucki says it will be a few years yet before Kepler is able to identify a true Earth analogue—a small planet on a one-Earth-year orbit around a sunlike star. Until then, astronomers are learning a great deal about a poorly understood midsize class of planets. "In our solar system we have no planets between the mass of Earth and the mass of Uranus, which is about 15 Earth masses," Jonathan Fortney of the University of California, Santa Cruz, a planetary scientist affiliated with the Kepler mission, said during the teleconference. "Now with the Kepler 11 system we have five more of these intermediate-mass planets to add to the three from previous exoplanet discoveries. We're still learning how nature makes planets in this intermediate mass range; however, it is clear that such planets need not resemble the Earth in any way." The low densities of the Kepler 11 planets imply a bounty of light elements and a dearth of iron and rock, making the midsize worlds more akin to mini Neptunes than to terrestrial, supersize Earths.
Having so many worlds in one system—and so many planets that spill their secrets via transits—may provide an exceptional test bed for theories of planetary formation and evolution. "Planetary science is very comparative," Fortney said. "Planets are so different from one another that you really need them to be in similar environments and then compare them to each other. And so in the Kepler 11 system we have just a fantastic laboratory, better than any other planetary system yet found, to look at the planets and compare them to one another to understand how these planets have evolved over time in kind of a contained system."
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29 Comments
Add CommentEvery discussion about possible extra-terrestrial life ALWAYS contains reference to the availability of water. The possibility of life elsewhere in a form totally unknown or even imagined by us, that DOES NOT require the presence of water is always ignored.
Reply | Report Abuse | Link to thisWhy?
Last week's modern miracle of non-aging mice has a certain implied and ominous portent of, say, having to live in 10 year shifts alternating with 20 years of suspended animation until galactic colonization can tidy up on humanity's excess proliferation. Or perhaps mulching the remains of those choosing virtual sublimation would be the optimal solution to Malthusian constraints. Hmm, this could be the solution to Fermi's paradox of the non-appearance of advanced civilizations - they've all sublimed off their planets. But only boring people are bored, don't sublime and the galaxy is ours!
Reply | Report Abuse | Link to thisThe problem with many of these exosystems is most of the exoplanets discovered so far have highly eliptical orbits. As a result, the gravitational effect of such planets in egg-shaped orbits eventually disrupts the orbits of any other planets in the system and will force the planets either into the parent sun or out into interstellar space.
Reply | Report Abuse | Link to thisWhat this article doesn't discuss in detail is the type of orbits of the system in Kepler 11. Are they close to circular (all orbits have to be somewhat eliptical) like in our system? Or are they highly eliptical like in the other exosystems we've found? If the orbits exceed certain eliptical parameters, an exosystem with multiple planets can't last very long.
So I would like to hear more detail about the orbits of the "earthlike" planets discovered so far and the orbits of the planets in their systems.
I believe you have answered your own question with "life elsewhere in a form totally unknown or even imagined by us." What would we look for? How would we conduct such a search? An why, when it is "life as we know it" that interests us?
Reply | Report Abuse | Link to thisPorscheVic: The reason for this is that we have no experience with non-water-based life. It would be scientifically erroneous for us to spend much time speculating on that possibility until 1: we are sure that it really is a possibility (that's not yet 100% certain) and 2: we actually have some real-world observations upon which to base our speculations. Nobody's doubting such life could exist, but then we can't really go around filling our more official scientific outlets with speculation about any and everything that "could" be true - each magazine would have to be the size of an entire encyclopedia to contain all the possibilities. We have to limit discussion to what is known and observed.
Reply | Report Abuse | Link to thisPauly D:
Reply | Report Abuse | Link to thisReuters story on this topic implies circular orbits at Kepler 11:
http://www.reuters.com/article/2011/02/02/us-space-planets-idUSTRE7117GY20110202
"In this case, the flickering light suggests a system of at least six planets, spinning rapidly around the star. One is orbiting farther out that the other five but they all appear to be made mostly of gas and orbiting in a very flat, circular plane."
Thanks for the link. The Reuters article states: "...The researchers can them [then] compute the planet's size and how quickly it is orbiting from this [transit] information."
Reply | Report Abuse | Link to thisI'm curious about the orbital velocities of these planets, but haven't found it clearly described. Circular orbits would imply that the system's gravitational effect is dominated by the stellar mass, despite the apparent proximity of the planets.
At any rate, it would be ironic if the rotational curve of this system is not consistent with Kepler's laws of Planetary Motion. Please, if there orbital velocities of these planets are not a function of their distance from the (dynamic) center of collective mass, it is _not_ evidence for the existence of dark matter!
FYI - the Nature article supplemental information can be had for free:
http://www.nature.com/nature/journal/v470/n7332/extref/nature09760-s1.pdf
Yeah, there are also good reasons to pick water as a by far the most suitable solvent medium. It has a relatively high specific heat, it is one of the most polar molecules known, and is overall just about the best solvent there is for a wide array of solutes. It is also ubiquitous, being made from 2 very common elements. You would simply be hard pressed to suggest another substance which would credibly fill this role in an environment even remotely Earth-like.
Reply | Report Abuse | Link to thisOne could imagine radically different chemical systems, and at our present level of knowledge it would be foolish to say that life cannot exist without water, but it seems like a very good place to start.
Why is it that all extrasolar worlds have orbit periods of minutes or hours at the most? Not even Mercury here on our solar system has such a short year!
Reply | Report Abuse | Link to thisI guess it doesn't matter where planets are claimed to be found. No one will ever go there to check it out in person.
Reply | Report Abuse | Link to thisWhy?
No spacecraft will be available in the foreseeable future. The distances to the stars are just too great. Not "sort of" too great, but EXTREMELY too great - by many orders of magnitude.
So, dream on.
I think the orbital velocity would be a function of the gravitational effects produced by the collective mass and the objects' distance from the collective center of mass: relatively large planets in proximal orbits produce high orbital velocities.
Reply | Report Abuse | Link to thisThese planets may be candidates for eventual collision with their stellar host, but I don't do math.
Why do some you fine people continue to posit that water and oxygen are the sole two main ingredients of exo-life? Tossing the oft-quoted, and almost iron-clad 'standard theory" into the already over-engineered trash can, and looking at the much bigger picture, one could easily create hypothetic conditions where elements that we are quite aware here on this particular planet/solar system may not exist in exoplanteary systems, and, elements that we are not familiar with could easily exist elsewhere in vast quantities. With that being said, alternate forms are carbon, water, etc are undoubtedly possible.
Reply | Report Abuse | Link to thisJust because the periodic table 'works here', that does not hold 100% true elsewhere, where different types of radiation may be incurred, creating different chemical makeups, etc. If one continues to posit the third main ingredient being carbon, is it impossible that there are different forms of carbon? Basic, higer level, lower level, the possibility does exist. Da?
....So, you ask, why create and discuss hypothetic conditions, where there is currently none that are 'scientifically asertained'...Because we can.
That in itself is the very foundation of scientific research. To ask Why, and then understand why or why not. And then be 100% correct on the solution, not just in a general agreement with a bunch of like-minded people.
...Gravity was once a hypothetic condition, until somebody took the time to figure out what was going on; same thing applies to exo-life. It is there, it is unexplained, and it is our job to figure out ALL the possibilities, not just the 'commonly accepted values' that we are currently comfortable with.
Thanks
Ed Wolinski
Hi, Good morning,i am Rahul,26,from INDIA,
Reply | Report Abuse | Link to thisi Believe our Rebirth is also on other planets as Aliens; in that planets Aliens Life span is 1,000years,or 10,000years,or 100,000years; in that planets Aliens Live without polution(They use solar energy,not use petrol,diesel Like us);They are Looking so Beautiful compare to us(not Like as Hollywood film Aliens);God created Not only our Dirty planet,he also created,good world's,for who people did good Things,in their past Life;if God is not Here,Then all planets,stars(suns),Asteroids,Black Holes are collapsed (crushed by Accident);
i Think There is No Hell and No Heaven; God created only Hell Type of planets(Like our planet)& Heaven Type of planets;
i Think There is No Ghost. if There is Ghost, Then God Didn't created our planets&universe; Because,Ghost Destroy our planets & universe; only ourr past Life karma is Deside our Luck or Bad Luck; But suicide is Not Death;
Note:There are 9 planets,100 moons in our solar system,There are 10,000crores above solar systems in our Galaxy,There are above 10,000crores Galaxies in our Universe; There are Lot of universes in space;
please Read science fiction Novels(Arther c.clarke Novels&short list of Arther c.clarke Award Novels(from 20 years));please send your Response to me; THANK U!;
Rahul, you are free to believe whatever you want. However, I highly encourage you to look up what ‘fiction’ means, to help you distinguish between reality and science fiction. Not only that, it would be good for you to look up punctuation and capitalization rules as well. Posts like this make me want to tear my eyes out, especially since I’m from the same country as you are. I mean this in the nicest way possible, of course. :)
Reply | Report Abuse | Link to thisAddressing the discussion at hand, there *are* researchers out there speculating the possibilities of lifeforms and elements that aren't similar to what we have here. It’s a feast for the imagination!
Reply | Report Abuse | Link to thisBut, remember, this is really just the first step towards studying other planets. Why *wouldn’t* we first look for Earth-like planets? Wouldn’t that give you a thrill, knowing that a planet exists out there on which we could potentially live? No one’s ruling out possibilities for the existence of things completely different from what we’re familiar with. Even laws may differ, as jtdwyer mused. We have a lot left to explore, and this is just a tiny step in that direction.
havent you heard of teleportation, time travel, suspemded animation and wormholes?????
Reply | Report Abuse | Link to thishey, haven't you ever heard of wormholes,teleportation,time travel and suspended animation?
Reply | Report Abuse | Link to this...And you were doing so well, before! :)
Reply | Report Abuse | Link to thisAlso, thanks, but rather than laws being different, I suspect that some of our established laws may require rescoping.
Again,I think that the laws of Planetary Motion mostly apply to exceedingly centralized configurations of mass and therefor, gravitational effects. Some orbital systems fit that criteria much better than others.
Probably because these exoplanets are detected by measuring the change in a sun's light output caused by the transit of the planet across the sun. Therefore, for at least the early discoveries, the results will be skewed toward fast transit times as we will see the periodic "dimming" of a sun's light more frequently and therefore be able to confirm it more quickly. I suspect that after a number of years this research will be able to confirm the existence of some slower moving planets.
Reply | Report Abuse | Link to thisWhat concerns me was the mention of this being a 3.5 year mission, that does not seem to me to be enough time to get some really useful data. I suppose it could just be a "proof of concept" mission that will pave the way for future instruments. One can only hope that we will have the perserverance to follow through on this.
@Ashjay Well, it is not like we will be able to hop into a wormhole next week. ;) Although that would be awesome.
Reply | Report Abuse | Link to this@jtdwyer A study of different orbital systems and a potential revamping of our currently accepted laws would really be interesting! It would lead to an even deeper understanding of the space-time fabric. I look forward to seeing what they come up with!
Note to the mods: My apostrophes were eaten up in my two previous posts. They first showed up as boxes, which means they were not recognized at all, and now there is simply nothing at each apostrophe position. Just reporting it, in case you get this problem a lot. :)
With the exception of suspended animation, we have had no meaningful success in these areas. Even in the arena of suspendid animation the best we have done is suspend a pig for a few hours.
Reply | Report Abuse | Link to thisThere are many spacecraft that if properly designed could make the journey easily, it's just that we don't have big enough power sources developed yet, so there will be many space craft in the "foreseeable future" which could potentially make the journey. It's just people with negative mindset that limit the people who could create these things but telling them it's impossible until thousands of years have passed. Look at how fast the human race has gotten up into space, new technologies are becoming available every day, for all we know there could be teams working on a "warp drive" or some space travelling device that could allow "jumps" across space. Don't be so quick to say something can't happen when it obviously already is so close to becoming reality.
Reply | Report Abuse | Link to thisBecause funds are limited. A search for life must be narrowed down some by looking for life similar to ours or the task of searching becomes so huge it is impossible. It also serves us to look for planets habitable to our physiology for colonization possibilities. Life my exist in waterless environments, but looking on every planet would be a burden.
Reply | Report Abuse | Link to thisI've read several articles (cannot recall where so no links) that discuss other forms of life. Most recently was about possible life on Titan (I think it was Titan) They spoke of it living in liquid natural gas. I specifically recall them stating that due to the difference in surface tension, single cell organisms could reach 3m in dia. I've also read that silicon is chemically similar to carbon so silicon life is possible. You can find things on other possible life, but you need to do a bit of digging.
Reply | Report Abuse | Link to thisYes, and although I know of no research into the technology, artificially created gravitational fields could easily create FTL transport. It may be future tech, but it is theoretically possible.
Reply | Report Abuse | Link to thisMany spacecraft are "nearly" able to go to the stars, huh? Just show me one single one that isn't strictly science fiction. You don't seem to understand basic financial reality . . . among other things.
Reply | Report Abuse | Link to thisIt is strange how so many people seem to be so sure that Life can be found anywhere that conditions are mild enough for it's survival. They seem to think that Life just naturally develops in any warm mud puddle. I think that sounds VERY ignorant.
Who, in their right mind would claim that the arrow head they found in a newly plowed field was formed by natural processes of wind and weather? Only a moron would claim that. It is scientifically obvious that an intelligent craftsman was at work to form that object.
Life is like that arrow head, in that it is obviously designed to include a complex mathematical Code (in Base 4 annotation) to allow accurate reproduction. Any mutations tend to be weeded out of populations, rather than being saved for possible future use.
The notion that Life is the natural result of some recipe of chemicals, is based on the same kind of ignorance that afflicted the old alchemists when they imagined they could cook up real gold from a recipe of cheaper materials.
That wasn't possible to do then, and it is not possible for Life to develop without intelligent input now. Or ever, for that matter.
So, I say, Dream on. Just don't call your dreams science. After you can DEMONSTRATE a significant star ship then, let's talk.
For a site that has info on extraterrestrials, UFO, 2012 and much more
Reply | Report Abuse | Link to thishttp://www.educatinghumanity.com
The reason they look for planets with liquid water is because these type of worlds offer a more protected environment for life to take hold. If the environment is to hot water boils and evaporates and any life form would shrivel bake and die. To far away and any liquid would freeze solid. If liquid water is present than thats a good indicator the environment could be suitable for life as we know it.There could also be liquid methane as is found on the moon Titan which could harbor life.But is high unlikely considering how cold the environment is on Titan. There's also liquid Nitrogen or Ammonia which could potentially harbor life although we use it to destroy micro organisms here on earth. There also liquid water with various chemicals in solution like sulfuric acid and hydrochloric acid which actually harbor some form of life here on earth. The one celled organisms that thrive in such environments are known as extremaphiles. My bet is they will find such extreme life forms in liquid pools on planet Mars and other moons of distant planets right in our own solar system
Reply | Report Abuse | Link to thisOur ability to travel or even communicate over distances of thousands of light years has not even approached our ability to observe over these distances. I would suggest concentrating efforts to distances that would relate to abilities possible in a human lifetime or less. It would seem so much more realistic.
Reply | Report Abuse | Link to this