First Earth-Like Planet Discovered!

So How often do we think we are going to see the headline announcing the discovery of the “First Earth-Like Planet” ? The latest example (CoRoT-7 b) came just as the New Year arrived. It turned out to be a firey world with temperatures ranging between -210 to 2000 degrees centigrade because it is tidally locked with its star. That’s not what most of us would consider Earth-Like. It earned its dubious title by being a rocky planet not very different in size than Earth.

Even as the news broke the sense of deja-vu was overwhelmingly strong. The previous “First Earth-like planet” (Gliese 581g) had been discovered just four months previously. This one is in the Goldilocks zone of its star meaning that it is at the right distance for liquid water to form on the planet. However, water would only actually form if it was rotating to give the surface an even temperature, but this one is probably tidal locked too.

Looking back through the news archives it is no surprise to find that news of the first Earth-like planets first appeared as far back as 1998 when just a handful of exoplanets were known. since then there have been a number of candidates, hopefully with each one being a little bit more Earth-like than its predecessor, although it is also the case that some of these discoveries later turn out to be errors.

At viXra log we confidently predict that the next collection of such headlines will hit us when the next major update from the Keplar mission is released on February the first, if not before. The pre-release of info about CoRoT-7 b may however signal that nothing much better has been found. In any case we can be sure that planets described as more and more Earth-like will be appearing for many years to come.

So what do we really think should be counted as an Earth-like planet? The data we get from Keplar and other observations should tell us about the planet’s size, mass, and distance from its star. From this information we can infer its average temperature, whether it is likely to be tidally locked, the strength of its surface gravity. Then from this we can make a guess about whether it could support liquid oceans of water, and an atmosphere of the right density as well as whether it has a molten iron-rich core. the latter is important because it could give the planet a magnetic field that protects it from radiation.

If “Earth-like” means a planet could support an ecosystem like ours it will need to be in the Goldilocks zone of a star that is not too dim so that it does not tidally lock and liquid water can exist. It will also need to have a size and density reasonably close to Earth’s. That will ensure that it can retain its atmosphere without it becoming too dense. It also means that large land based animals will not be hindered by excess gravity and the molten core will not solidify to remove the magnetic field as it did on Mars.

It follows form these considerations that the star around which the planet orbits must also be like our Sol. If it were less bright the planet would need to get nearer and would be tidally locked. Bigger stars tend not to last long enough to provide a stable environment in which life can evolve. Other types of star may be too variable in brightness, or may have regular deadly flares that could strip any nearby planet of its atmosphere, even with the protection of a magnetic field.

Taking these things into consideration, the parameters that we can currently measure of exoplanets and the stars they orbit need to be very close to those of Earth and our Sun.

Apart from these considerations, an important feature of our planet is its large moon. Without it there would be no tides and these have surely been very important in promoting the evolution of live. The Moon is also said to keep our planet’s rotation axis stable. If it were otherwise we might suffer catastrophic changes in climate that would ruin the atmosphere of our planet. There may be an outside chance that Kepler could see the presence of such a moon as the system transits in front of its star.

Even if a star meets these requirements it really just makes it potentially Earth-like. The planet also needs to have the right chemical mix of elements in the right quantities to make oceans and an atmosphere that would support rather than poison life. Will we ever be able to detect their presence?

After Keplar has made a long (hopefully) list of potentially Earth-like exoplanets the next step will be to examine them more closely using other observatories. The best hope of being able to do this in the foreseeable future lies with the James Webb Space Telescope that is due for launch in 2014. The JWST will have spectrometers sensitive enough to see the slight differences in a systems spectra when planets pass behind their stars. It will even have a special camera with a spot that can block out the light from a star so that some planets can be seen away from the glare. This should certainly be good enough to work for the gas giants but it may require the next generation of space telescope to be able to do the same for smaller (potentially) Earth-like planets.

In the long term the prospects for finding truly Earth-like planets can only get better. Just how fast depends on technological and economic developments that are hard to predict. Ultimately there is no reason why we should not be able to determine the chemical composition of the atmospheres of Earth-sized exoplanets and if they have the right proportions of oxygen and nitrogen we will know that Earth-like plant and animal life must be present. Perhaps we will even be able to see the tale-tale signature of chlorophyl or other molecules that can only be produced in quantity by vegetation. That’s  if such planets even exist nearby.

In any case one thing is for sure:  Headlines telling us of the “First Earth-like Planets” are going to be around for some time.

17 Responses to First Earth-Like Planet Discovered!

  1. Bornerdogge says:

    Is there any chance the new 30- to 40-meters telescopes planned for the next 10 years will be capable of imaging close-to-earth-sized planets with enough details to detect signs of life-based activity or get a direct spectrum?

    PS: I think the telescope is named “Kepler” and not “Keplar” ;)

    • Philip Gibbs says:

      That’s a good question and I wont pretend to have the definitive answer. I think that even with good adaptive optics it is going to by hard to see a planet within the glare of a star through the atmosphere. I think this is the domain of space based telescopes of the future.

  2. Lawrence B. Crowell says:

    The new flash, “Earth-like Planet Discovered” really means we found a rocky or terrestrial planet. This planet is probably Earth-like in the same manner Mercury and Venus are “Earth-like.” This planet pretty much looks like burnt toast, and you can be sure that the hot side is an ocean of lava. The cooler side of the planet probably has snow or hail storms of condensing silicon and vaporized rock. This planet looks like a pretty dismal piece of astronomical real estate for life to exist.

    Optical telescopes will probably move back to the ground. Adaptive optics should be able to overcome atmospheric problems. The future for space based telescopes is in the IR and UV and above to X-ray and γ-ray where you have atmospheric absorption.

    Cheers LC

  3. Luboš Motl says:

    Well, when NASA calls 2000 °C “warm” planets to be oh so nicely Earth-like and hospitable for life, it surely makes a complete sense when James Hansen of the same NASA says that 0.6 °C of temperature change is one-half of the route to hell and extinction. Or is it? ;-)

    • Lawrence B. Crowell says:

      I fail to see how this matter of extra-solar planets has anything to do with climate heating by CO_2.

      • Luboš Motl says:

        I completely share your sentiment. In fact, there is *no* warming worth talking about by CO2 on planets anywhere in the Universe that have at most a trace amount of CO2.

      • Lawrence B. Crowell says:

        It is pretty widely known that if the Earth had no CO_2 in its atmosphere temperatures would be about (IIRC) 20C colder. CO_2 loves IR, and has a huge cross section for it. A couple of years ago I read a little short about how the tenuous martian atmosphere even has some stimulated emission of IR.

        The problem of CO_2 and warming is that it poses a bit of a problem for the secular theology of economics.

      • Luboš Motl says:

        This is complete nonsense, Lawrence. You are confusing carbon dioxide and water. What is true is that if the Earth had no greenhouse gases, the surface would be about 30 deg C colder. But 85-95 percent of this greenhouse effect is due to H2O molecules: water is by far the most important greenhouse gas. The entire greenhouse effect of all CO2 in the atmosphere – including the natural one – is between 2 and 5 deg C and we may have added 0.5 deg C to that.

        At any rate, my point was completely uncontroversial, namely that NASA is being inconsistent because it employs people who claim that a Celsius degree of temperature change is almost lethally dangerous while its “extraterrestrial departments” classify planets with temperatures differing by thousands of degrees as being hospitable for life.

        Needless to say, the truth is in between – temperature fluctuations by something like 50 Celsius degrees are just OK for life, as we know from the Earth. Temperature changes much smaller than 50 Celsius degrees don’t represent a problem, and temperature changes much greater than 50 Celsius degrees represent a problem.

      • Bill K says:

        This is not the place to debate global warming, but I’d just like to point out that the definition of “Earth-like” must include long-term stability, over a 100 My to 1 Gy time scale. Orbital stability, along with climatic stability from other causes. Earth has apparently gone through several extreme episodes in the past where life “as we know it” was dealt a global setback, and took millions of years to recover. If the Permian extinction or the Snowball Earth had been any more severe, the effect might have been permanent.

      • Lawrence B. Crowell says:

        Water is important because of its abundance, but CO_2 has a high cross section for IR. An overview is at:

        http://en.wikipedia.org/wiki/Greenhouse_effect

        I don’t particularly want to debate this, but it is pretty clear that those who study this topic and know WTF they are talking about are saying something very different from what you claim

        I think this is only nonsense from the perspective of a pretty inflexible political and economic perspective.

        @ Bill, The Earth has gone through various climate changes in the past. Most of them are transient on a geological time scale. A glacial period lasts a few 10s of thousands of years with a 10 thousand year interstadial. This has marked the Pleistocene for the last 1.5 million years. We are in an interstadial, and we should be entering into the next glacial period in fact. There is some thinking that with CO_2 release with the start of agriculture there has been a sort of pre-industrial global warming.

        The problem is something we are simply going to have to manage. I don’t think we can over the next 2 decades make the 40% carbon cuts advocated, though I suspect we will reach some “peak carbon” before 2050. Petroleum is likely to peak this decade and our output decline, and coal is thought to peak out before mid century. So CO_2 output will decline one way or the other. I suspect we will have to work on some of these geo-engineering schemes to reflect about .5% of average solar energy or about 1watt/m^2 from the Earth. This will require a delicate combination of national politics, industries on the private level and international diplomacy.

        There was a song I remember listening to in high school by the band “Devo,” with the line “When you have a problem, you must whip it.” That is my take on it. We don’t deny it, we don’t panic — we whip it.

      • Philip Gibbs says:

        I think earth’s climate is a little off topic for this post and I can see this getting out of hand, so please just agree to disagree!

      • Philip Gibbs says:

        Bill, I agree with your comment about stability which is why I mentioned the need for a stable sun like ours. the moon helps too.

        On the other hand, in an ecosystem which is too stable, lifeforms tend to settle into niches and once all niches are filled evolution itself can stop with lifeforms that are not necessarily very advanced. This has been seen in some ecosystems on Earth where some animals have remain unchanged for many millions of years.

        If there had been no asteroid strike to get rid of the dinosaurs the more advanced mammal species would probably never have had a chance to prosper as larger animals. I think that other changes such as periodic ice-ages, shifting continents as well as the accasional catastrophy were essential to disrupt stable ecosystems so that more advanced animals could develop. We are lucky to live on a planet where there was enough disruption to bring about animals as advanced as us without life ever having been set back to square one.

      • Luboš Motl says:

        I agree, Phil, that some refreshment and tests of resilience are helpful to evolve more advanced life forms. After all, the most advanced civilizations also didn’t grow up in the regions where all the humans had bananas falling into their mouths for free. I hope this damn obvious fact won’t be considered racist here.

        I can’t believe that someone may try to dispute the elementary fact that most of the IR absorption in the atmosphere is by H2O, see elementary, totally well-known graphs of these phenomena, e.g.

  4. Bill K says:

    A frequent theme of early science fiction stories was “terraforming,” i.e. ecological engineering to transform an inhospitable world into something rather Earth-like. Examples are Heinlein’s “Farmer in the Sky” and Herbert’s “Dune” series. They always oversimplified, assuming that all you need is a little water, a little oxygen, some nonextreme temperature and you’re all set to go. Grind up the lava, drop in a few earthworms, and pretty soon you’re proudly raising golden waves of grain.

    What else does it take? The right metallic content, for one thing. Shielding from UV, less than hurricane force winds, a reasonable day-night cycle, freedom from volcanic eruptions and giant meteor strikes, etc. Such conditions are difficult to determine from a distance, and without them, calling a planet Earth-like is being wildly overoptimistic.

    Also, the sci-fi writers neglected the reverse possibility of “antiterraforming”. That through misguided human activity, a perfectly nice planet like ours can be made more suitable for other types of life forms.

    • Lawrence B. Crowell says:

      Terraforming is likely to remain completely in the domain of fiction. Ultimately you are changing the chemistry of a region, which in the first law means an application of free energy to drive – μdN in some direction. Of course we humans are doing the opposite; we are increasing entropy through chemical changes — burning fossil fuels, generating CO_2, dumping PCBs in water, throwing trash around and so forth. That is what might be called anti-terraforming, or engineering a mass extinction event. It seems the antithesis of the anthropic principle is that we are garbage making meat machines.

      There is a bit of an observer bias with extrasolar planets. Planets which orbit close to their stars exert more gravitational pull, enhancing the Doppler effect and its frequency, or they are more likely to transit the star. This is one reason we know about so many superhot Jovian or Torch Jovian planets. Now that we are looking at rocky planets we have found a number of these lava planets. Some might be a bit like comets with vaporized rock being jettisoned in a tail.

  5. Bill K says:

    “… the most advanced civilizations also didn’t grow up in the regions where all the humans had bananas falling into their mouths for free. I hope this damn obvious fact won’t be considered racist here.”

    Somewhat. But mostly, naive and superficial. What causes a culture to “advance” is a complex question, and easy abundance of food is not the leading factor. If it were, our own culture would be stagnant, and people in Ethiopia would have advanced beyond us.

    “I can’t believe that someone may try to dispute the elementary fact that most of the IR absorption in the atmosphere is by H2O.”

    Here’s the difference: H2O is self-limiting. Whenever too much H2O accumulates in the atmosphere — it rains! Or clouds form, thereby increasing the planet’s albedo. Aerosols are extremely important in regulating climate, and quite difficult to model.

    • Lawrence B. Crowell says:

      With extrasolar planets the gold standard is just to find some chemical signatures within some planetary atmosphere which are signatures of life. An oxygenated atmosphere with traces of methane might do well. A photosynthetic planet similar to Earth will also have some spectral signatures we might recognize. That of course assumes some universality to chlorophyll, which is questionable. As for advanced life forms which are intelligent, forming something analogous to a “civilization,” it is my sense that the closest one might be 50 or 100 million light years away. I hold that the Copernican principle does imply intelligent life elsewhere, but I suspect it might imply one ET per 100 or 1000 galaxies or something like that. If SETI manages to get a signal I will happily polish off a bottle of Glenfiddich , both in joy over the discovery and trouble with what I would see as some implications of it.

      As for H_2O, it is a bit strange to think that people who eat breathe and drink climate science do not have its role properly in place.

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