Far-Off Planets Like the Earth Dot the Galaxy

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The known odds of something — or someone — living far, far away from Earth improved beyond astronomers’ boldest dreams on Monday.

Astronomers reported that there could be as many as 40 billion habitable Earth-size planets in the galaxy, based on a new analysis of data fromNASA’s Kepler spacecraft.

One out of every five sunlike stars in the galaxy has a planet the size of Earth circling it in the Goldilocks zone — not too hot, not too cold — where surface temperatures should be compatible with liquid water, according to a herculean three-year calculation based on data from the Kepler spacecraft by Erik Petigura, a graduate student at the University of California, Berkeley.

Mr. Petigura’s analysis represents a major step toward the main goal of the Kepler mission, which was to measure what fraction of sunlike stars in the galaxy have Earth-size planets. Sometimes called eta-Earth, it is an important factor in the so-called Drake equation used to estimate the number of intelligent civilizations in the universe. Mr. Petigura’s paper, published Monday in the journal Proceedings of the National Academy of Sciences, puts another smiley face on a cosmos that has gotten increasingly friendly and fecund-looking over the last 20 years.

Written By: Dennis Overbye
continue to source article at nytimes.com

26 COMMENTS

  1. @OP – One out of every five sunlike stars in the galaxy has a planet the size of Earth circling it in the Goldilocks zone — not too hot, not too cold — where surface temperatures should be compatible with liquid water,

    I have made this point before about the popular press getting carried away about “habitable planets”. There very likely are habitable planets, but it takes a lot more than being around “Earth size” and being in a suitable orbital temperature zone, to make a planet “habitable”.
    The abundance of elements (metalicity) in its star’s planetary system is one, its spin and association with moons is another, and its position in the galaxy is the third. (Some areas of our galaxy are very hostile to life or to the duration of planets.)

    • In reply to #1 by Alan4discussion:

      @OP – One out of every five sunlike stars in the galaxy has a planet the size of Earth circling it in the Goldilocks zone — not too hot, not too cold — where surface temperatures should be compatible with liquid water,

      I have made this point before about the popular press getting carried away about…

      Couldn’t agree more. However much I want to one day hear the news that we have found a planet that DOES harbor life elsewhere in the galaxy…. However much I DO believe there is life elsewhere, the media always go for the spectacular headline and neglects the important details which in turn tends to generate popular misconception in the greater public about these discoveries.

      One thing the media SHOULD focus on however is how difficult it will be to find a planet like ours and emphasize how precious our own earth really is. My personal belief is that we’ll have to look long and hard before we find one comparable to ours.

      • In reply to #5 by NearlyNakedApe:

        In reply to #1 by Alan4discussion:

        One thing the media SHOULD focus on however is how difficult it will be to find a planet like ours and emphasize how precious our own earth really is. My personal belief is that we’ll have to look long and hard before we find one comparable to ours.

        As far a human colonies go, we do not need an Earth like planet to have colonies. If we set up space bases mining asteroids or comets, we could use these as resources to live in space and travel on them to very distant places. Big space bases could have rotation to provide gravity. Many comets already have elliptical orbits which go way out to the edge of the outer Solar System – part way to the nearest stars.

        http://www.planetaryresources.com/

        With large supplies of water, metals and ceramics and 3D printers to manufacture components, many structures in space are possible.

        Water ice can be separated into hydrogen and oxygen for humans or for rocket fuel – there is almost limitless solar thermal or photovoltaic energy in the inner Solar System.

        http://www.space.com/21773-3d-printing-asteroid-mining-telescope-parts.html

        http://www.planet-science.com/categories/over-11s/space/2012/04/mining-in-space.aspx

  2. Hm…is anyone getting a bit depressed by the fact that there are probably heaps of civilizations out there in the galaxy, but, at least from what I understand, it is very improbable humanity will ever make any kind of contact with them, due to the vastness of the distances involved and myriad other almost impossible-to-overcome constraints? I know I am, a bit :P

    • In reply to #2 by JoxerTheMighty:

      Hm…is anyone getting a bit depressed by the fact that there are probably heaps of civilizations out there in the galaxy, but, at least from what I understand, it is very improbable humanity will ever make any kind of contact with them, due to the vastness of the distances involved and myriad other almost impossible-to-overcome constraints?

      Not really, no. I’m still pretty much convinced that, despite the increased probability of other “Earth-like” planets being out there, the probability of any of those planets actually bearing life is still extremely low, the probability of intelligent life having evolved on those planets is much, much lower, and the probability of any intelligent life on any of those planets creating the type of civilization that we would even recognize (let alone be able to communicate with), is so low as to be practically non-existent.

      So, no, I’m not depressed that we will likely never make contact with all the other civilizations out there. I’m depressed at the thought that we might actually be alone in the universe and that when we are gone the universe will cease to have any “meaning” whatsoever (since meaning is something that can only be assessed by intelligent beings).

    • In reply to #2 by JoxerTheMighty:

      Hm…is anyone getting a bit depressed by the fact that there are probably heaps of civilizations out there in the galaxy, but, at least from what I understand, it is very improbable humanity will ever make any kind of contact with them, due to the vastness of the distances involved and myriad other…

      I’m depressed by the fact that we are in the process of destroying the one and only habitable planet we currently know about.

      • Red Dog,
        I had my students google images of “the Pacific Garbage Vortex” Monday. It was very disturbing and I felt like crying. Some day soon, we will be able to walk on the swirling pile of garbage. Our descendants may build houses on it! It is big enough at present to qualify as an American State. Oh, and there are TWO of them. I am sad.

        In reply to #4 by Red Dog:

        In reply to #2 by JoxerTheMighty:

        Hm…is anyone getting a bit depressed by the fact that there are probably heaps of civilizations out there in the galaxy, but, at least from what I understand, it is very improbable humanity will ever make any kind of contact with them, due to the vastness of the…

  3. Something I have always found peculiar. We presume physics, chemistry and biochemistry are identical all over the universe. Yet the default is to assume earth is unique in supporting life. I would have thought the default should be “it similar elsewhere to the way it is here until proven otherwise.”

    To me the idea that there is only one planet in the universe has life is preposterously improbable. It would either have to be 0 or a large number. The only way I can see someone could entertain such a strange notion is to believe man is god’s favourite being and the whole universe was created for his delectation. Let p be the probability of life arising on an average planet. What are the constraints on the value of p for there to be precisely one life-bearing planet?

    • In reply to #6 by Roedy:

      The only way I can see someone could entertain such a strange notion is to believe man is god’s favourite being and the whole universe was created for his delectation.

      Au contraire! In fact, back when I was a believer, I more readily entertained the notion that the universe was filled with intelligent life specifically because it made no sense (to me, at least) that God would create this entire vast universe just for our benefit.

      Yes, we presume physics, chemistry and biochemistry are identical all over the universe, but we (and by “we” I mean “I”) also presume that the formation of life is not something that occurs whenever the proper conditions are available. Which is why, I would argue, we only have one instance of life arising on this planet; if it were not such a mind-bogglingly rare event, then it would have happened repeatedly here on Earth.

      But, even if you want to assume that life of some sort or another is more or less likely to arise whenever the correct conditions are present, how likely is it that intelligent life will evolve? Again, look at our own history and the number of times intelligence has arisen here.

      And then, even if you want to assume that intelligent life is more or less likely to arise wherever there is life, what are the odds that that intelligence will be the sort that would build civilizations anything like we would recognize and could communicate with? You could argue that whales and octopi are intelligent, but they are not likely to be emitting radio waves into the ether any time soon.

      Again, all of this is just my own ruminations on the subject. I suspect that the odds of there being any other intelligent civilizations elsewhere in the universe (let alone the galaxy) are pretty slim. Rather than seeing this as proof of God’s existence, however, it makes me really cherish just how special each and every intelligence is on this pale blue dot of a planet. It’s humbling to think how small we are in relation to the vastness of the universe, but also ennobling to think that we might actually be unique within all the cosmos.

    • In reply to #6 by Roedy:

      Something I have always found peculiar. We presume physics, chemistry and biochemistry are identical all over the universe. Yet the default is to assume earth is unique in supporting life.

      I don’t know who you are referring to that takes that as the default but I agree anyone who does isn’t doing good science. But taking any answer as “the default” isn’t right. The default should be to say we don’t know until we have evidence that points one way or another. The point about physics, etc. being the same is irrelevant. The issue isn’t does physics still work the same way or would natural selection still occur once we had some basic form of life, the answers to both those questions are of course yes, the relevant questions (which we don’t have good answers to yet) are how exactly did life come to exist on Earth, what were the circumstances that enabled it, and how common are those circumstances in the rest of the galaxy.

      To me the idea that there is only one planet in the universe has life is preposterously improbable.

      That is a gut feeling. For what it’s worth (nothing) my gut feeling is the same. As Carl Sagan said on this topic “I try not to think with my gut”

      It would either have to be 0 or a large number.

      Why? How is that good science to make an assumption that your answer has to be in some discontinuous range of possible results with no rational justification?

      The only way I can see someone could entertain such a strange notion is to believe man is god’s favourite being and the whole universe was created for his delectation.

      What if it turns out that a large number of highly improbable events have to take place in order to enable the environment in which life can arise? For example, there were some researchers a while back who claimed that not only did an earth like planet need to be in the goldilocks zone but it also required a single moon with the unique kind of orbit that our moon has. I didn’t find the argument very convincing but at least theoretically it is possible.

      • In reply to #9 by Red Dog:

        What if it turns out that a large number of highly improbable events have to take place in order to enable the environment in which life can arise?

        Even if the conditions for life to arise are so rare that our planet is the only one out of the 40 billion in our galaxy to have succeeded, let’s not forget that there are as many as 200 billion galaxies in the universe. And don’t get me started on the multiverse! lol

        • I agree. Even if you say that only one in every billion planets will have the conditions for life to form, that still leaves you with billions of planets with life on them.

          In reply to #10 by Billions and Billions:

          In reply to #9 by Red Dog:

          What if it turns out that a large number of highly improbable events have to take place in order to enable the environment in which life can arise?

          Even if the conditions for life to arise are so rare that our planet is the only one out of the 40 billion in our galaxy to…

          • In reply to #13 by Ryan1306:

            I agree. Even if you say that only one in every billion planets will have the conditions for life to form, that still leaves you with billions of planets with life on them.

            Yes, but out of those possible billions of planets with some sort of life, how many have complex life? And how many of those with complex life have intelligent life? And how many of those with intelligent life have something we would recognize as civilizations?

            I never said I thought we were the only form of life in the entire universe. My point was that we may be the only advanced civilization to have arisen. I think that is orders of magnitudes less likely than the mere existence of life (which may be pretty improbably to begin with).

          • Advanced intelligent species would be the minority (if they exist at all). Most planets with life would probably have only simple organism, which was the case for the Earth for a few billion years. As far as other beings developing a sophisticated culture, we toiled in a hunter gatherer existence for over a hundred thousand years but we were able to eventually, through the collection of knowledge, evolve into the society we have today.

            I’ll end though by agreeing with Red Dog that it is tough to make any real predictions about the abundance of life in the universe with the data we have now, but when I think with my gut, I can’t help but to agree with Roedy and think that life can’t be so rare that with trillions of opportunities it’s never happened again. To me that would be miraculous in it’s self. Just my two cents.

            In reply to #14 by godzillatemple:

            In reply to #13 by Ryan1306:

            I agree. Even if you say that only one in every billion planets will have the conditions for life to form, that still leaves you with billions of planets with life on them.

            Yes, but out of those possible billions of planets with some sort of life, how many have complex…

          • In reply to #14 by godzillatemple:

            In reply to #13 by Ryan1306:

            I agree. Even if you say that only one in every billion planets will have the conditions for life to form, that still leaves you with billions of planets with life on them.

            Yes, but out of those possible billions of planets with some sort of life, how many have complex…

            Look, I may have overexaggerated about “heaps of civilizations in the galaxy”(then again, I might not), and I’m just a layman, but I really doubt about being the only civilization in the universe. We’re talking about such astronomical numbers, than if we assume there is one civilization every 1000 galaxies, there still would be millions of civilizations throughout the universe. Truth be told, these “armchair” estimations don’t really lead anywhere at all, but we can all hypothesize I guess on what our thoughts are on this…

          • In reply to #18 by JoxerTheMighty:

            Truth be told, these “armchair” estimations don’t really lead anywhere at all, but we can all hypothesize I guess on what our thoughts are on this…

            Yep, that’s what it all boils down to. Just my personal opinion that we may be the only civilization out there, but there’s really no way to tell for sure unless we actually find evidence of another civilization out there. Given the vast distances involved and the fact that any evidence is likely to be either lost amid the noise or not recognized as such, I’m not holding my breath…

        • In reply to #10 by Billions and Billions:

          In reply to #9 by Red Dog:

          What if it turns out that a large number of highly improbable events have to take place in order to enable the environment in which life can arise?

          Even if the conditions for life to arise are so rare that our planet is the only one out of the 40 billion in our galaxy to…

          I’m not trying to advocate for any point of view here. Neither that we are or aren’t alone. I’m just saying that based on what we know there are so many unknowns that all we can do is speculate. As I said, if I had to give my honest gut feeling it is that we almost certainly aren’t the only intelligent life in the Universe and probably not in the galaxy and I hope one day we find other civilizations. Although I agree with Hawking that based on our experiences on Earth meeting another civilization might not turn out that well for at least one of us.

          Regarding life in other galaxies, given our current technology and any technology we can imagine based on our current theoretical knowledge life in other galaxies may as well be in other universes, we won’t be able to observe it much less communicate with it.

  4. Sean Carroll shared some interesting thoughts about the possibility of intelligent life elsewhere: Billions of Worlds

    This bit is particularly interesting:

    I don’t have strong feelings one way or another, but I suspect that more credence should be given to a somewhat disturbing possibility: the Enlightentment/Boredom Hypothesis (EBH).

    The EBH is basically the idea that life is kind of like tic-tac-toe. It’s fun for a while, but eventually you figure it out, and after that it gets kind of boring.

  5. Again and again, when it comes to intelligent live, most people fail to take into consideration TIME. They seem to think that all intelligent life, wherever it may be, will progress at a similar rate to intelligent life on earth and therefore share our timeline.

    For me, intelligent life throughout the universe might never coexist at the same time.

    Does anyone know if there is an equation that deals with the possibility of two intelligent species coexisting within our universe?

    • In reply to #20 by veggiemanuk:
      >

      Does anyone know if there is an equation that deals with the possibility of two intelligent species coexisting within our universe?

      A general guide would be the age of the local stars in a group, and the metalicity of the systems. It takes a few local supernova explosions to produce the heavy elements that are probably needed for life, so second or third generation stars are likely to be needed in that locality. The positive side of this is that metalicity tends to be in local concentrations, so life supporting stars with heavy elements, could be in the same star cluster, having formed around the same time, from the same gas cloud.

    • In reply to #20 by veggiemanuk:

      Does anyone know if there is an equation that deals with the possibility of two intelligent species coexisting within our universe?

      Have you heard of the Drake equation That is pretty much what it does, it gives a formula for calculating the probability that we will encounter another intelligent species. I think it backs up the point I’ve been making about how we can’t do more than speculate right now. There are several variables in that equation where we really have no idea what the value should be right now.

      • In reply to #22 by Red Dog:

        Have you heard of the Drake equation That is pretty much what it does, it gives a formula for calculating the probability that we will encounter another intelligent species. I think it backs up the point I’ve been making about how we can’t do more than speculate right now. There are several variables in that equation where we really have no idea what the value should be right now.

        There are also a number of problems with missing factors from the Drake equation, some of which I pointed out earlier. (They are probably omitted because much less was known when Drake produced this formula.) Your link covers some of these issues.

        Even if planets are in the (Goldilocks) habitable zone, however, the number of planets with the right proportion of elements is difficult to estimate.[36] Brad Gibson, Yeshe Fenner, and Charley Lineweaver determined that about 10% of star systems in the Milky Way galaxy are hospitable to life, by having heavy elements, being far from supernovae and being stable for a sufficient time.[37]

        Heavy elements are a key issue, because the absence of carbon, and the absence of a planetary rocky surface or iron core, make the possibility of life very remote.

        Supernovae are necessary to generate heavy elements, but life really does not want to have one going off in the next-door star!

        Also, the Rare Earth hypothesis, which posits that conditions for intelligent life are quite rare, has advanced a set of arguments based on the Drake equation that the number of planets or satellites that could support life is small, and quite possibly limited to Earth alone; in this case, the estimate of ne would be almost infinitesimally small.

        The discovery of numerous gas giants in close orbit with their stars has introduced doubt that life-supporting planets commonly survive the formation of their stellar systems.

        Gas giants orbiting near the habitable zone would disrupt orbits, move planets into new or eccentric orbits, and cause loss of moons or planetary collisions. Any close orbiting, gas-giants migrating outwards (conservation of angular momentum) would massively disrupt rocky planet formation or orbits.

        In addition, most stars in our galaxy are red dwarfs, which flare violently, mostly in X-rays, a property not conducive to life as we know it. Simulations also suggest that these bursts erode planetary atmosphere.

        Flares of damaging radiation from the log-lived red dwarfs would be a problem, as would any star systems near the highly active centre of the galaxy.

        Having said that, there are potentially billions of planets and those with a high metalicity could be in systems grouped together.

        OHooligan@23 I like “commonplace” better than “rare”, others don’t, and that’s just a matter of taste.

        I think there are factors well beyond what we “like”! Lack of metalicity, hard radiation, being run-over by a gas giant planet, or lacking plate-tectonics to recycle an atmosphere, are pretty dire deterrents for life!

      • In reply to #22 by Red Dog:

        In reply to #20 by veggiemanuk:

        Does anyone know if there is an equation that deals with the possibility of two intelligent species coexisting within our universe?

        Have you heard of the Drake equation That is pretty much what it does, it gives a formula for calculating the probability that we will…

        Still, it seems the emphasis is still put in all life evolving around the universe at the same time in step with life on earth, even the mention of intelligent life still get’s stuck with the now.

        What I’m getting at is the likely hood that intelligent life develops at different times around the universe but never coexists. Or am I missing something?

        • In reply to #25 by veggiemanuk:

          Still, it seems the emphasis is still put in all life evolving around the universe at the same time in step with life on earth, even the mention of intelligent life still get’s stuck with the now.

          No, I don’t think that is correct. From what I remember the equation explicitly DOES take those things into account. I.e., the probabilities in the Drake Equation include factoring in how long intelligent civilizations will require to become intelligent and how long they will last as a species. The Drake equation is specifically designed to answer the question you are asking, not just how likely is it that an alien intelligence will arise somewhere but how likely it will arise in a way that overlaps with our civilization and we actually are able to detect each other while both species are still living.

  6. I see the rare vs commonplace discussion has re-awoken. Each new piece of evidence shifts the probability one way or the other, this time it appears to be nudged towards “commonplace”. I like “commonplace” better than “rare”, others don’t, and that’s just a matter of taste.

    The truth is we don’t know, can’t know (from the evidence available so far), and there’s lots more to find out so let’s keep on working towards narrowing the bounds on the terms of the Drake equation.

    But even if the heavens are teeming with life, as we know it and/or as we don’t, the distances make it unlikely that we’ll meet up any time soon.

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