Billions of Earthlike Planets Found in Milky Way

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Tens of billions of Earthlike worlds are strewn across the Milky Way, many of them circling stars very much like our own sun, astronomers said today.


Earlier research suggested that rocky planets might be much more abundant around small stars than sunlike ones.

But a fresh analysis of data from NASA’s Kepler mission, which launched in 2009, suggests this is not the case, according to new research presented at the annual meeting of the American Astronomical Society in Long Beach, California.

“We found that the occurrence of small planets around large stars was underestimated,” said astronomer Francois Fressin, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

A Starry Night … Full of Planets

To find planets, Kepler stares at a patch of sky in the constellation Cygnus, made up of about 150,000 stars. The space telescope detects potential alien worlds by watching for telltale dips in starlight created when planets pass in front of, or “transit,” their parent stars.

Using their own independent software for analyzing Kepler’s potential planet detections, Fressin and his colleagues estimate that about 17 percent, or one in six, of all the sunlike stars in the Milky Way host a rocky planet that orbits closer than the distance at which Mercury orbits our own sun.

Written By: Ker Than
continue to source article at news.nationalgeographic.com

26 COMMENTS

  1. The Drake Equation gets a little less vague as science sees ever more clearly what surrounds us.

    These discoveries are soooo much more awesome than viral memeplexes of old mythtakes….

    We may never find other ‘intelligent’ life forms, but the possibilities multiply via our curiosity.

    The results coming from our scientific minds, methods & technologies are truely inspiring.

  2. Oh ho! And carbon on mercury too. I mustn’t become too ecstatic, but if asteroids did deposit it, how many other planets got some as well? Where did this stuff come from? I’ve got butterflies in my stomach. This is just staggering.

  3. We can’t-we’re speechless-it’s amazing-awesome. Well done, Kepler – now, wouldn’t the man himself be proud!

    Isn’t it telling that it’s NASA’s Kepler mission that made those discoveries and not NASA’s St.Pius the Fifth or Urban the Eighth or any other of the eleven popes that presided over the Vatican in Kepler’s lifetime?

    Even his own epitaph is far superior to any papal pronouncement or chant:

    “I measured the skies, now the shadows I measure

    Skybound was the mind, earthbound the body rests.”

    How humble (and ungodly and atheistic!), and how fitting that now he is still ‘measuring the skies’ and finding planets!

    In reply to #3 by Ali Duncan:

    I want to be an astrophysicist, but I don’t really know if I can even spell the word. You people with a clue, speak up.

  4. I keep looking at this and wondering if it’s a hoax, or whether I’m out of touch, but this looks like a massive advance to me. I was stunned enough by the solar system found at Ceti Tau, but this is simply overwhelming to me.

  5. Using their own independent software for analyzing Kepler’s potential planet detections, Fressin and his colleagues estimate that about 17 percent, or one in six, of all the sunlike stars in the Milky Way host a rocky planet that orbits closer than the distance at which Mercury orbits our own sun.

    You would expect to find rocky planets in the inner part of solar systems where the solar radiation and solar wind has vaporised volatiles and blasted off atmospheres. It is also easier to find planets in short orbits close to their stars.

    More care in analysis is needed for rocky moons in outer systems. These are easily distinguished from gas giants by the differences in density and spectrum, but water etc. is “a rock”, in the outer Solar System!

  6. Only a little. There remains the thorny issue of those factors concerning the prevalence of life, intelligent life and technological life. What they may be is the huge unknown.

    In reply to #1 by CdnMacAtheist:

    The Drake Equation gets a little less vague as science sees ever more clearly what surrounds us.

    These discoveries are soooo much more awesome than viral memeplexes of old mythtakes….

    We may never find other ‘intelligent’ life forms, but the possibilities multiply via our curiosity.

    The results coming from our scientific minds, methods & technologies are truely inspiring.

  7. Tens of billions of Earthlike worlds are strewn across the Milky Way, many of them circling stars very much like our own sun, astronomers said today.

    I would suspect, that the headline is a journalistic exaggeration.
    Most of them are more likely to “Mercury-like”, “Venus-like”, or Mars-like”, than Earth-like”!

  8. In reply to #9 by papa lazaru:

    ‘Found’…

    Yeah right. Could you please stop with those sensationalist headlines?

    Oh of course not…

    I agree but I’m more bothered by “Earth like”, to most people it implies a planet with an atmosphere, oxygen, water, etc. when what they really mean is essentially a solid planet rather than a gas giant.

  9. chock full of rocky worlds

    A certain ice cream company (based in Texas) sent packets aboard a trip to the ISS.

    It would be cool if they made a special design for ‘rocky road’ flavor per this announcement.
    Hurry before another certain company beats ya to it!

  10. What a wonderful and exhilarating time to be alive. How everything comes together; the stupendous progress in technology, the LHC in Geneva, the construction of ever larger and better telescopes like the Webb telescope and the E-ELT, the discoveries in cosmology and astronomy, the detection of countless strange and possibly habitable worlds. The prospect of finding alien life in our lifetime (I have another 40 years or so to go). Planets of diamond, golden meteorites, oceans of methane. Hopeful signs from the study of abiogenesis, the glorious and liberating facts of evolution, the ever better understanding of – chemically driven – human behaviour, the medical advances and the increase of life expectancy. And, of course, the internet, that will spell the death of religion, or at least the lunacy of the Abrahamic faiths. The God of the Gaps becoming the God of the Tiny Cracks.

    Imagine the Torah, the Bible or the Koran, all three maybe an inch and a half thick. Filled with anachronistic rubbish. Compare that to the scientific literature, stretching hundreds of kilometers, accumulated over the last, say 600 years. It’s a done deal who will be victorious.

  11. I can imagine Bill Reilly’s reaction:

    “How dey get there? Tell me that. How dey get there?”

    Well Bill, they were put there by that giant squid who just allowed himself to be photographed in the Pacific!

    Reality is truly far more wonderful than fiction. Although fiction can be pretty darn good also. I wonder if they’ll ever find Magriahea, where planets are built to order?

    http://www.bbc.co.uk/cult/hitchhikers/guide/magrathea.shtml

  12. Thank you for your balmy response. Agreed on the papal nonsense, agreed and inspired by the multiplicity of meanings in Keplers epitaph, noting how efficient the assertion that Kepler still operates through his conferred understanding seems. What a legacy. Whatever else you say, surely, you could not question Keplers existence, as you could Christs. I’m a bit drunk atm..

    In reply to #4 by HenMie:

    We can’t-we’re speechless-it’s amazing-awesome. Well done, Kepler – now, wouldn’t the man himself be proud!Isn’t it telling that it’s NASA’s Kepler mission that made those discoveries and not NASA’s St.Pius the Fifth or Urban the Eighth or any other of the eleven popes that presided over the Vatican in Kepler’s lifetime?Even his own epitaph is far superior to any papal pronouncement or chant:”I measured the skies, now the shadows I measureSkybound was the mind, earthbound the body rests.”How humble (and ungodly and atheistic!), and how fitting that now he is still ‘measuring the skies’ and finding planets!In reply to #3 by Ali Duncan:I want to be an astrophysicist, but I don’t really know if I can even spell the word. You people with a clue, speak up.

  13. In reply to #8 by Alan4discussion:

    … Most of them are more likely to “Mercury-like”, “Venus-like”, or Mars-like”, than Earth-like”!

    I commented elsewhere on how we don’t know enough to make a clear call between “rare” and “commonplace” for life in the universe, and how we therefore adopt whichever we prefer. Your “more likely” is an expression of your preference, I think.

    Of course, if you define “Earth-like” to mean has a single large moon and lots of permanently liquid water and an axial tilt of twentysomething degrees and an island the right size and shape for building Manhattan on, they, yes, that’s probably quite rare. Even without Manhattan, I just threw that one in gratuitously.

    While we still don’t know “enough” (and I don’t suppose we ever will), this latest report does seem to tilt the balance a bit more towards Commonplace. Which is my preference, so this pleases me. I know the technology isn’t quite up to detecting earth-sized planets in the Goldilocks-Zone, even if they are there, but, still, these results are pretty amazing. Billions and Billions, to misquote Carl Sagan. I’m sure he’d have been delighted to see this.

  14. In reply to #20 by OHooligan:

    In reply to #8 by Alan4discussion:

    … Most of them are more likely to “Mercury-like”, “Venus-like”, or Mars-like”, than Earth-like”!

    I commented elsewhere on how we don’t know enough to make a clear call between “rare” and “commonplace” for life in the universe, and how we therefore adopt whichever we prefer. Your “more likely” is an expression of your preference, I think.

    Nope! Some people may make claims according to fancy, but my claim is based on the history of rocky planet formation in the Solar System, as far as we understand it, with later delivery of water to Earth .

    Of course, if you define “Earth-like” to mean has a single large moon and lots of permanently liquid water and an axial tilt of twentysomething degrees

    Those would look like features which greatly improve probability of life starting and persisting on Earth. Certainly for anything resembling Earth-life.

    There are many features in planetary formation and orbital development which would be very counter-productive to abiogenesis or time spans of favourable climate permitting evolution. Many of them have been measured and studied on the planets and moons of the Solar System.

    While we still don’t know “enough” (and I don’t suppose we ever will), this latest report does seem to tilt the balance a bit more towards Commonplace.

    We don’t know for certain if life elsewhere is common or not on Earth-type planets or in Earth-like conditions.
    We do know the sort of conditions likely to stop developments, or exterminate life. These conditions are very common!

    Which is my preference, so this pleases me.

    You should know fanciful thinking is no basis for scientific opinions. There are gaps in our knowledge, but much information is competently researched and on record.

    I know the technology isn’t quite up to detecting earth-sized planets in the Goldilocks-Zone, even if they are there, but, still, these results are pretty amazing. Billions and Billions, to misquote Carl Sagan. I’m sure he’d have been delighted to see this.

    Statistically we can expect some Earth-sized planets or Earth-mass planets. But: – Earth TYPE planets are likely to be very rare, due to the mechanisms of their (physical) evolution, the variations in star-types, accretion disks, planet types, and the distribution of chemical elements in galaxies.

  15. Thanks Alan4 for the patient and detailed response. I was aware of some of the things you mention but not in depth.

    I wasn’t aware of anything suggesting the mix of elements used by life on earth was in any way rare, I had the impression that the chemistry of life depends only on the most commonplace of elements composed in the earliest generations of stars.

    Noting the way that life on earth has spread to fill every niche, I’d be surprised to find it is so picky or fragile that it can only survive on The Perfect Planet.

    In the interests of honesty I’ve declared my preference (for Life Is Commonplace), but I wouldn’t have the temerity to call it a Scientific Opinion, being no expert, and I think I’m open to evidence either way.

    However, I suspect that proponents of the Rare Earth hypothesis – and therefore the “Life Is Rare” proposition – are overly inclined to whittle down the numbers by insisting that features that just happen to exist here are actually essential for life to flourish – hence my absurd comment about Manhattan. Knowing now that lots of stars have rocky inner planets (detected, not conjecture), the Goldilocks Zone rocky ones (as yet undetectable) may also be commonplace, along with plenty of “dirty snowball” comets to provide water, therefore water-rich rocky planets don’t seem all that special, and the number of stars is so vast that still allows “Billions and Billions”.

    I’ve seen Continental Drift/Plate Tectonics go from “don’t be stupid” to “accepted fact” since I was at school, not that this is relevant except to note that expert scientific opinion is subject to change in face of new evidence, as it should be. I would be delighted to see Rare Earth refuted, and I wondered why. I think it is because I see it as one more step along the trail blazed by Copernicus and Galileo, away from Man and Earth as the center of creation, a position that I loathe.

    In some ways I’m more interested in the psychology of preference – Commonplace vs Rare – than in the specific arguments, but only as long as neither has been refuted.

    Meanwhile, the astronomers (and the other astro-scientists) continue to amaze me. Interesting Times.

  16. In reply to #23 by OHooligan:

    Thanks Alan4 for the patient and detailed response. I was aware of some of the things you mention but not in depth.

    Here are a few more details:-

    I wasn’t aware of anything suggesting the mix of elements used by life on earth was in any way rare, I had the impression that the chemistry of life depends only on the most commonplace of elements composed in the earliest generations of stars.

    arxiv.org/abs/1209.3778Detailed Abundances of Two Very Metal-Poor Stars in Dwarf Galaxies – The most metal-poor stars in dwarf spheroidal galaxies (dSphs) can show the nucleosynthetic patterns of one or a few supernovae. These supernovae could have zero metallicity, making metal-poor dSph stars the closest surviving links to Population III stars. Metal-poor dSph stars also help to reveal the formation mechanism of the Milky Way halo.

    BTW in astronomy ” metallicity”, refers to heavy elements (including Carbon and Oxygen) not just metals in a chemical sense. So you might see a problem for life in a system lacking carbon and oxygen.

    Noting the way that life on earth has spread to fill every niche, I’d be surprised to find it is so picky or fragile that it can only survive on The Perfect Planet.

    en.wikipedia.org/wiki/Globular_cluster
    No known globular clusters display active star formation, which is consistent with the view that globular clusters are typically the oldest objects in the Galaxy, and were among the first collections of stars to form. Very large regions of star formation known as super star clusters, such as Westerlund 1 in the Milky Way, may be the precursors of globular clusters.[23]
    Composition

    ▬▬▬▬▬▬
    Djorgovski 1′s stars contain hydrogen and helium, but not much else. In astronomical terms, they are described as “metal-poor”. [24]

    Globular clusters are generally composed of hundreds of thousands of low-metal, old stars. The type of stars found in a globular cluster are similar to those in the bulge of a spiral galaxy but confined to a volume of only a few million cubic parsecs. They are free of gas and dust and it is presumed that all of the gas and dust was long ago turned into stars.

    Globular clusters can contain a high density of stars; on average about 0.4 stars per cubic parsec, increasing to 100 or 1000 stars per cubic parsec in the core of the cluster.[25] The typical distance between stars in a globular cluster is about 1 light year,[26] but at its core, the separation is comparable to the size of the Solar System (100 to 1000 times closer than stars near the Solar System).[27]

    However, they are not thought to be favorable locations for the survival of planetary systems. Planetary orbits are dynamically unstable within the cores of dense clusters because of the perturbations of passing stars. A planet orbiting at 1 astronomical unit around a star that is within the core of a dense cluster such as 47 Tucanae would only survive on the order of 108 years.

    However, I suspect that proponents of the Rare Earth hypothesis – and therefore the “Life Is Rare” proposition – are overly inclined to whittle down the numbers by insisting that features that just happen to exist here are actually essential for life to flourish – hence my absurd comment about Manhattan. Knowing now that lots of stars have rocky inner planets (detected, not conjecture), the Goldilocks Zone rocky ones (as yet undetectable) may also be commonplace, along with plenty of “dirty snowball” comets to provide water, therefore water-rich rocky planets don’t seem all that special, and the number of stars is so vast that still allows “Billions and Billions”.

    Rocky planets which can keep an atmosphere, without becoming like Venus or the core of a gas giant are special.

    You could count up the “rocky planets”, rocky “dwarf planets” and planet-size moons in the metal rich solar system, but it only looks as if one or possibly 2 or 3 could have life.

    I’ve seen Continental Drift/Plate Tectonics go from “don’t be stupid” to “accepted fact” since I was at school, not that this is relevant except to note that expert scientific opinion is subject to change in face of new evidence, as it should be.

    Plate tectonics is one of the features which makes Earth rare. Earth is very hot and active, with a liquid interior, AND a fairly thin solid (but broken) crust, AND liquid water on its surface which masks, cools and suppresses under-sea volcanic eruptions as well as redistributing heat all over the planet for billions of years without the oceans boiling off.

    I would be delighted to see Rare Earth refuted, and I wondered why. I think it is because I see it as one more step along the trail blazed by Copernicus and Galileo, away from Man and Earth as the center of creation, a position that I loathe.

    This is not a scientific reason.

    In some ways I’m more interested in the psychology of preference – Commonplace vs Rare – than in the specific arguments, but only as long as neither has been refuted.

    Meanwhile, the astronomers (and the other astro-scientists) continue to amaze me. Interesting Times.

    I do not think anyone is likely to refute that the Earth is rare in terms of percentages of types of planets.

    How extensive a range of conditions can support possible diverse life forms is another matter.

    What we can say, is that Earth-type life is unlikely around stars which cannot maintain planetary systems for significant time periods, or on planets lacking heavier elements like carbon and oxygen.

    It would also seem unlikely on planets with huge temperature variations – the sort of variations which can be created by sychonicity, axial instability, or an elliptical or eccentric orbit.

    The term “rocky planet” can also be misleading. Water is a rock in the outer Solar System – with some “rocky-moons” appearing to have large quantities of it in their “rocks” – not to mention erupting it from their volcanoes!

  17. Once again, Alan4, thank you. I’ve got some interesting reading ahead of me.

    In declaring my preference, I wasn’t claiming a Scientific Reason, just a psychological one. And it’s only a preference, not a faith.

    One other thought: given the steps needed to get to life on earth as it is now, is this planet “ahead of the curve”, perhaps among the first, or has there been enough time for life elsewhere to have evolved to earthlike complexity a long time ago? 13 billion years might seem long, but is it only just long enough, or have there (potentially) been pockets of similar complexity (say) 6 billion years ago?

    I’d appreciate your comments on this.

  18. In reply to #26 by OHooligan:

    Once again, Alan4, thank you. I’ve got some interesting reading ahead of me.

    One other thought: given the steps needed to get to life on earth as it is now, is this planet “ahead of the curve”, perhaps among the first, or has there been enough time for life elsewhere to have evolved to earthlike complexity a long time ago? 13 billion years might seem long, but is it only just long enough, or have there (potentially) been pockets of similar complexity (say) 6 billion years ago?

    I’d appreciate your comments on this.

    With only one example of DNA /RNA based life, we really don’t know.
    We do know that some star-types look less favourable than others, but the good news, is that our patch of spiral arm looks “metal-rich” and more favourable than many other places.

    What is happening in other galaxies, is too far away to have much relevance to us in the foreseeable future.

    Life looks doubtful (at least by our criteria) in the outer Milkyway with various “metal-poor patches”, also near the galactic centre, where there is a lot of high energy activity.

    A lot of the characteristics of a planet and it’s expected life-span, depend on the size and type of its star.

    aspire.cosmic-ray.org/labs/star_life/hr_interactive

    The evolutionary sequences for stars are described by their position on a graph called the Hertzsprung-Russell (H-R) diagram. Most stages of stellar evolution, beginning with protostars, have a specific position on the H-R diagram. The different branches of the H-R diagram described below will be referred to throughout the descriptions of the evolutionary sequences for different mass stars that follow. – chandra.harvard.edu/edu/formal/stellar

    The Hertzsprung-Russell (H-R) Diagram – Alt Text

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