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Gliese 581 is a diminutive red-dwarf star located in the constellation Libra at a distance of about 20 light years. You can’t see it with your eyes---you’ll need a really good telescope. It’s also one of the most exciting stars in the sky right now.

Now, the sky is about full of diminutive red-dwarves. In fact, the majority of the stars within 30 light years of us happen to be them. They’re just there—they burn long. They live long. And they’re dim. They’re so dim that if our star had a red-dwarf companion out past Pluto, we’d barely see it if we saw it at all, and yes, there is a hypothesis that the Sun does indeed have a red-dwarf companion that has an orbit of roughly 26 million years. If it exists, it may have been spotted by WISE which scanned the skies in the infrared, whose data set is publically available and being analyzed by research teams all over the world.

In 2007 the first of what we now know is probably six planets were detected around Gliese 581. Now, they weren’t directly imaged. Doing that is difficult although, it has been done, several times. Rather, they were detected via radial velocity. As planets orbit a star they tug on it. These tugs are detectable, and from there, one can tease out a great deal of data, including a planet’s mass, its orbital period, and its orbital eccentricity. Perhaps even now, somewhere in the galaxy, alien astronomers are viewing a region of space that includes our sun and noting the presence of perhaps 4 large worlds (those worlds being Jupiter, Saturn, Uranus, and Neptune). Perhaps they’ve even teased Earth out of their data set. But I digress.

The planet detected in 2007 doesn’t really have a name. We call it Gliese 581 c. It’s probably a hot, unpleasant place. Its minimum mass is 5.6 Earth Masses.  It hugs its sun so closely that its year is two weeks long.  It’s likely tidally locked, its surface roiled by steaming, blazing, horror-storms of fire.

Other worlds orbit Gliese 581, at close range to their star. The most exciting one though, is the one labeled “g.” It’s also the most controversial.

Does it Exist?

In 2010, news broke that planet “g” was discovered, and it orbited within Gliese 581’s habitable zone. A habitable zone is the zone around any star where water can exist in liquid form. Life as we know it here on Earth requires water, and it’s a fair assumption that this will be replicated across the universe.

Planet g was not the first planet detected within the habitable zone of a star. At 55 Cancri, a sun-like star located about 40 light-years from us, a large, Saturn-sized planet was detected orbiting roughly where water would be liquid. What’s exciting about Planet g is that it’s fairly small. In fact, its mass at minimum just 2.2Earth masses.

However, the planet’s existence was in doubt from the beginning. Only one team of planet-hunters detected the world. Other Planet-Hunters could not detect the characteristic “pull” that would signify that it existed.

On October 11, 2010, an astronomer from the Geneva Observatory's HARPS project announced at the IAU Symposium 276 that their team had not been able to confirm the existence of either planetary candidates Gliese 581 "g" or "f" based on only their own, expanded but smaller dataset of 180 observations over 6.5 years. Simulations based on their data have shown that the probability that the radial-velocity variations can be produced "by chance" because the noise is not negligible. This is because the signal amplitude of "g" and "f" are very low and close to the level of the measurement noise (Leslie Mullen, Astrobiology, October 12, 2010; and Rachel Courtland, New Scientist, October 13, 2010).
Basically put, the planet was just a data artifact. It isn’t real. I was very sad after that news broke.

New research (from the same research team) suggests that planet “g” is indeed real.

Now the original discoverers of Gliese 581g, led by Steven S. Vogt of UC Santa Cruz, present a new analysis with an extended dataset from the HARPS instrument that shows more promising evidence for its existence. The new analysis strengthens their original assumption that all the planets around Gliese 581 are in circular and not elliptical orbits as currently believed. It is under this likely assumption that the Gliese 581g signal appears in the new data.

“This signal has a False Alarm Probability of < 4% and is consistent with a planet of minimum mass 2.2M [Earth masses], orbiting squarely in the star’s Habitable Zone at 0.13 AU, where liquid water on planetary surfaces is a distinct possibility” said Vogt.

Based on the new data Gliese 581g probably has a radius not larger than 1.5 times Earth radii. It receives about the same light flux as Earth does from the Sun due to its closer orbital position around a dim red dwarf star. These factors combine to make Gliese 581g  the most Earth-like planet known with an Earth Similarity Index, a measure of Earth-likeness from zero to one, of 0.92 and higher than the previously top candidate Gliese 667Cc, discovered last year.

Actual paper can be read here.  Obviously, debate will continue as to whether it exists or not.

Now, what kind of place is planet “G”? Probably habitable, but not very nice for human life.

It swings about its star in just 37 days. If it exists, one face likely faces its star at all times, and one away. This is called tidal locking. The best example? Our moon. Now, it’s possible that interactions with the star system’s other planets have forced a slow rotation. Perhaps it’s in resonance with the other worlds such as for every three rotations, it orbits its star two times. This is why Mercury isn’t tidally locked with the Sun.  But we don’t know this, from our far vantage point at 20 light-years away.

With its minimum mass of 2.2M, it possibly is 1.3 to 1.5 times larger than Earth if it’s a rocky planet, and gravity at its surface is 1.1 to 1.7 times that of Earth’s. If we could go there (again, assuming it exists), we’d feel a lot heavier, for starters. Walk around long enough here, and you'll get thighs that can choke a horse and a butt you could bounce quarters off of.

What kind of weather would this place have? Not very nice weather. It’s been speculated that a planet that doesn’t rotate would have a hellacious “Hot-Pole” and a dark and arctic “Cold-Pole.” Early simulations in the days before computers speculated that the atmosphere would freeze out completely. Later simulations suggested that a dense enough atmosphere would not freeze out at all, and that while the planet wouldn’t rotate, the atmosphere would via heat transfer. Essentially, the surface would be ridiculously windy, as hot air blew around the planet from the Hot Pole to the Cold Pole, and then back to the Hot Pole. It’d be a lot more complicated than that depending on the presence of liquid oceans and continental features such as mountains and plains, but that’s basically the idea. Both the Hot and Cold Poles would not exactly be habitable, but where the sun hangs just above or below the horizon might be temperate and nice, comparatively (this is called the terminator). This planet, being larger and denser than Earth, could have a comparatively thicker atmosphere. That atmosphere would pack a hefty punch when it got moving.

Now, if the planet isn’t tidally locked, but rotates every 3 times for every 2 orbits, then things get pretty darn weird and alien. You’d have a sunrise that’d take days to happen. On some days, the sun would retrograde (move backwards) through the sky.  The planet would rotate much too slowly for a Coriolis Effect, so perhaps there wouldn’t be any hurricanes or cyclonic storms as we know them. But perhaps the rising sun would also be accompanied by a great deal of rain, or snow turning to rain. Planetary local noon might be very hot. Seasons wouldn’t exactly matter either—or seasons would be synonymous with where a specific location is within the planetary day. Local noon might equal local summer. Sunset might come with heavy rain, changing to snow, as the sun sets, an event that’d take days. Local midnight might equal the depths of local winter.  In short, just like Denver. (Kidding!)

Barriers to Life

Red-Dwarves have a bad habit. They flare. A lot. And big ones.

Star-flares throw off a great deal of radiation. A planet close in could be completely sterilized. Now there are models that indicate that a thick enough atmosphere can absorb the radiation (ours does), thus maintaining its habitability. Flares, however, could over time erode away the atmosphere of such a world, orbiting close in. Gliese 581 is known to be variable, but it isn’t known to be violently variable like our sun’s nearest known stellar neighbor, Proxima Centauri. That’s a plus in “g’s” favor.

Another barrier is the type of light. Red-dwarves emit far more infrared light than they do visible light. Plants require visible light to perform photosynthesis, and using Earth as a dataset, we know that planets require a set range of temperatures to perform photosynthesis. It’s possible that plant-analogue life may develop that utilizes infrared light, but we don’t know that just yet. Perhaps the plantlife isn't green at all.

There will be much more debate over Gliese 581 g over the coming months as more data gets analyzed by different teams around the world. This is indeed an exciting time for planetary discovery. The Kepler telescope discovers new worlds every month and the knowledge that our solar system isn’t unique seems quite firm. The stars are full of worlds and perhaps life too. The only thing that makes me sad is it seems unlikely we’ll ever visit them. But if we could, tomorrow, I’d be the first to sign up to go.

What do you think? I've offered a lot of speculation on my part, now I want to hear yours.

Originally posted to SciTech on Mon Jul 23, 2012 at 11:18 AM PDT.

Also republished by Astro Kos and Community Spotlight.

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Comment Preferences

  •  I always feel so small when I read astronomy. (10+ / 0-)

    But also very reassured for some reason.

    Education is a progressive discovery of our own ignorance.

    by Horace Boothroyd III on Mon Jul 23, 2012 at 11:22:17 AM PDT

    •  As I grow older, I am more and more grateful (8+ / 0-)

      for how little of this I'm responsible for, and for how short a time.

    •  "for some reason..." (7+ / 0-)

      How'bout one or more of these:  

      Because as far as we know, the entire visible universe works in accord with the same laws of nature and physical theories that we discover here on Earth.  We, here, are part of something vast that is knowable.  

      Because you're recognizing intuitively, something that can be roughly estimated in math via the Drake equation for the probability of life elsewhere:  That any reasonable numbers one plugs into that equation produce the result that our universe is likely to be infested with life, and that this also means the presence of other intelligent species and other civilizations, some of which should be far more ancient and wise than our own.  

      Because awe, wonder, and curiosity, are natural and rational responses to perceiving something that is enormously larger than oneself.  

      Because recognizing any of these points, or similar ones stated in different language, leads to the feeling that at some level the universe at-large is our natural home: not only Earth, but potentially other planets in other star systems, and not only in the physical sense that humans may actually go there, but in a kind of "spiritual" sense of kinship or relatedness among all of life everywhere.  

      And because astronomy, physics, astrophysics, and some day astrobiology, will enable us to keep learning about this vast universe of ours, and from that knowledge will come real wisdom.  

      "Minus two votes for the Democrat" equals "plus one vote for the Republican." Arithmetic doesn't care about your feelings.

      by G2geek on Mon Jul 23, 2012 at 02:12:25 PM PDT

      [ Parent ]

      •  No, none of those. :) (4+ / 0-)
        Recommended by:
        G2geek, terrypinder, Quicklund, revbludge

        Even if I knew that tomorrow the world would go to pieces, I would still plant my apple tree. -Martin Luther

        by the fan man on Mon Jul 23, 2012 at 03:19:47 PM PDT

        [ Parent ]

        •  OK, then what? ;-) n/t (2+ / 0-)
          Recommended by:
          terrypinder, revbludge

          "Minus two votes for the Democrat" equals "plus one vote for the Republican." Arithmetic doesn't care about your feelings.

          by G2geek on Mon Jul 23, 2012 at 03:22:19 PM PDT

          [ Parent ]

          •  Um, I can't understand astronomy and that (3+ / 0-)
            Recommended by:
            G2geek, terrypinder, revbludge

            makes me feel small, but someone does understand it and that makes me feel reassured.

            Even if I knew that tomorrow the world would go to pieces, I would still plant my apple tree. -Martin Luther

            by the fan man on Mon Jul 23, 2012 at 03:39:39 PM PDT

            [ Parent ]

            •  it's good to know that we can... (3+ / 0-)
              Recommended by:
              terrypinder, the fan man, revbludge

              .... trust the people who work on these things, and that the process for producing scientific findings is good at correcting its mistakes along the way.  This is how we get an accurate picture of everything in nature: ideas are tested and cross-checked, and improved as new information comes in.  

              "Minus two votes for the Democrat" equals "plus one vote for the Republican." Arithmetic doesn't care about your feelings.

              by G2geek on Mon Jul 23, 2012 at 04:12:34 PM PDT

              [ Parent ]

              •  a cloud passes... (2+ / 0-)
                Recommended by:
                terrypinder, Aunt Pat

                NPR reporting this morning that there is a hue and cry for "public oversight" of scientific research in the wake of the bird flu mutation experiments.
                While a foreseeable response, it is a symptom of the times that we do not trust the people who work on these things anywhere near as much as we did decades ago (when they were playing around with increasing megaton yields of hydrogen bombs and making anthrax...)
                Meanwhile the funders of national campaigns and one of the contenders for the most powerful job in the world are utterly opaque.
                But it's the scientists that suddenly can't be trusted. And yes, this is being cynically used by those who true aim is to discredit science in general, and climate science in particular.

                So if it turns out Gliese 581g is habitable, but barely, can we make it a penal colony for these guys?

                Class war has consequences, and we are living them.

                by kamarvt on Tue Jul 24, 2012 at 04:40:03 AM PDT

                [ Parent ]

      •  This line of thought has always appealed to me. (1+ / 0-)
        Recommended by:
        Aunt Pat

        Sometimes I like looking at Hubble images or other high-resolution field shots and thinking: this image represents but a tiny, tiny fraction of a fraction of a percent of the visible universe. This image alone contains thousands upon thousands of galaxies, and that's merely the ones we can see. Each of those galaxies contains uncounted millions of stars. A nontrivial percentage of those stars are going to contain planets.

        It is impossible to follow this train of thought to its logical conclusions and not believe that our universe is not teeming with life in nearly infinite variety--let alone to maintain the arrogance necessary to assume that our planet is the sole repository of life.

        And that's not even getting into to incomparably vaster stretches of void between the stars. Just because there's no emissions or occlusion that we can detect doesn't mean there's truly nothing there.

        Sin lies only in hurting others unnecessarily. All other "sins" are invented nonsense.

        by Catsy on Tue Jul 24, 2012 at 01:08:13 PM PDT

        [ Parent ]

  •  Warp drive? Hell, I'll take a Bussard ramjet (12+ / 0-)

    It might take 100 years to get to Gliese but it won't violate any (known) rules of physics to do it. I'm glad so many groups are working so hard on exoplanet discovery. I hope we find some more 581g's out there. And maybe one will be saying "Hello" if we listen carefully enough.

    Many people thought Bush was "the kind of guy you wanted to have a beer with". People are beginning to realize that Romney is "the kind of guy you want to pour a beer on".

    by ontheleftcoast on Mon Jul 23, 2012 at 11:25:14 AM PDT

    •  Or a big ion drive, with the craft assembled in (10+ / 0-)

      earth orbit so it can carry heavy shielding.  You might be able to get there in 40 years, from the perspective of the crew.  Due to relativistic time dilation, however, centuries would have passed on Earth.

      The first space ship might well get there to find it already colonized by earthlings who left much later with faster ships.

      •  one of my favorite sites (8+ / 0-)

        speculates about such a craft.  pretty cool stuff!

        pseudoscience can kill

        by terrypinder on Mon Jul 23, 2012 at 12:11:56 PM PDT

        [ Parent ]

      •  nice; well said; and a great premise for fiction. (13+ / 0-)

        What you said:  "The first space ship might well get there to find it already colonized by earthlings who left much later with faster ships."

        That would also become a very interesting basis for a science fiction plot.  The technical details of this remain to be worked out, and for that matter is might not be technically plausible at all, but it makes for an interesting human story:

        As the Earth ship approaches the planet, the crew detects clear signs of a technological civilization: artificial light on the dark side, and electromagnetic radiation suggestive of radio communication.  

        At first they are hesitant to get any closer but the crew all agree that having come so far, they at least have the capacity to keep sending back data to Earth, and if they meet their death at the hands of this new civilization, at least they will have been able to warn Earth.  

        Then over a period of weeks or months, they continue observing and speculating about the life on this planet.  Eventually they decode the radio emissions and discover, to their great surprise, that they are in English.  

        With that, they make contact, and are greeted as the long lost mission that had since been overtaken by much faster ships carrying colonists from Earth, who have managed to establish a new civilization on this new planet.  

        Upon landing and disembarking, they are welcomed to their new home in a manner similar to a newly-discovered branch of a family is welcomed to a yearly holiday feast.  

        And no, there isn't some kind of nasty surprise waiting.  In our present dystopian era, there is need for stories that have happy endings after all.  

        "Minus two votes for the Democrat" equals "plus one vote for the Republican." Arithmetic doesn't care about your feelings.

        by G2geek on Mon Jul 23, 2012 at 02:29:03 PM PDT

        [ Parent ]

    •  Something like a nuclear-powered (3+ / 0-)
      Recommended by:
      ontheleftcoast, ozsea1, terrypinder

      VASIMR rocket for a "TAU" craft ("Thousand-Astronomical-Unit") automated science station that could park well outside the helioshock and Oort cloud and take some super-awesome clear pictures with a Webb-style telescope... (assuming Webb works as advertised...)

      ...ah, the mind salivates at the notion!  

      •  So what's up with VASIMYR anyway? (1+ / 0-)
        Recommended by:

        I Googled it to see how the testing is going (haven't seen anything for a year or so) and along with the normal articles and it's own site, a bunch of 'VASIMYR is a lie and an Obama conspiracy!!' popped up. Obviously when I see 'Obama conspiracy', it's auto-ignored as insane wackjobbery so I didn't even bother, but what is their problem with VASIMYR? And is there any progress with it? Who can enlighten me?

        Romney 2012 - Enough.... is never enough. (Ferengi Rule of Acquisition #97)

        by Fordmandalay on Tue Jul 24, 2012 at 08:15:01 AM PDT

        [ Parent ]

  •  thank you for an interesting post. (14+ / 0-)

    I get all sorts of great info from DKOs.

    I have to admit, though that

    Gliese 581g Probably Exists After All
    had me thinking it was referring to a DKOs username.

    As my father used to say,"We have the best government money can buy."

    by BPARTR on Mon Jul 23, 2012 at 11:26:13 AM PDT

  •  Life exists in some pretty extreme conditions (10+ / 0-)

    here on Earth.

    It could probably manage on 581 g.

  •  Hope it is closer to 1.5 Earth radii. (3+ / 0-)
    Recommended by:
    terrypinder, jim in IA, G2geek

    Would've been more hopeful if that were the lower limit; 1.5 for 2.2 Earth masses means a very similar potential at the surface to Earth.

    •  Mass and radius (2+ / 0-)
      Recommended by:
      terrypinder, Aunt Pat

      Assuming the same density as Earth (a fairly large assumption):  

      The mass of a planet is proportional to the cube of its radius.

      The force of gravity between two objects is proportional to the square of the distance between them.  

      So, if a planet's mass is 2.2 times ours, its radius is the cube root of 2.2, or 1.3 times ours.  

      Let m be a small object's mass, M be Earth's mass, r be Earth's radius, M' be Gliese 581g's mass, and r' be Gliese 581g's radius.  

      F(earth) = GmM/r^2

      M' = 2.2M
      r' = 1.3r

      F(Gliese) = Gm*(2.2M)/(1.3r)^2
                     = 2.2GmM/1.69r^2
                     = 1.30*F(earth)

      America has already run the experiment of increasing human mass by 30% -- the consequences aren't great but neither are overweight Americans sprawled helplessly on the ground.  

      "Politics should be the part-time profession of every citizen who would protect the rights and privileges of free people and who would preserve what is good and fruitful in our national heritage." -- Lucille Ball

      by Yamaneko2 on Tue Jul 24, 2012 at 04:01:19 AM PDT

      [ Parent ]

  •  Oh, I should have added (5+ / 0-)

    "What color is the sky".

    I am looking for the link that I found some time ago surfing the net late at night, but the sky would  not be red. It'd be whiteish.

    (Yes, that means Vulcan's red sky from Star Trek is all wrong, although they got it right in the new movie.)

    pseudoscience can kill

    by terrypinder on Mon Jul 23, 2012 at 12:04:34 PM PDT

  •  I believe Life is the default condition. If it (5+ / 0-)
    Recommended by:
    terrypinder, jim in IA, Aspe4, G2geek, ozsea1

    can exist someplace, it will.  Sentiency requires stability, but simple organisms are more robust and survive here in extreme environments (e.g. deep water thermal vent organisms require no sunlight for energy and are complex biologically) ...  Maybe radiation shielded turtles... Who knows?  Nature has better imagination than I do :-)  In any case, cool stuff.

    The third-rate mind is only happy when it is thinking with the majority. The second-rate mind is only happy when it is thinking with the minority. The first-rate mind is only happy when it is thinking. A. A. Milne

    by Memory Corrupted on Mon Jul 23, 2012 at 12:47:24 PM PDT

    •  yes, and yes. (2+ / 0-)
      Recommended by:
      terrypinder, ozsea1

      This also means that any life-bearing planet, given a long enough period of stable conditions, will probably develop intelligent life.  

      The next barrier to overcome is the ability of intelligent organisms to make tools: for example we know that elephants and large marine mammals such as dolphins have behaviors indicative of intelligence and social organization, but they don't have the physical means to develop complex tools (hands with opposable thumbs, or equivalent means of closely manipulating objects).

      And after that, a brain structure that is wired to detect consistency and inconsistency: the basis of science and therefore technology.  

      And then, some means of using stored energy.  After that, a form of social organization that does not self-destruct.

      But whatever reasonable numbers you plug into those variables, you still end up with many intelligent civilizations in our galaxy.

      "Minus two votes for the Democrat" equals "plus one vote for the Republican." Arithmetic doesn't care about your feelings.

      by G2geek on Mon Jul 23, 2012 at 02:34:59 PM PDT

      [ Parent ]

      •  A minor point (2+ / 0-)
        Recommended by:
        terrypinder, Wee Mama

        In the book Guns, Germs and Steel, Jared Diamond makes an excellent point about the development of human civilization that I think needs to be considered.

        Humans developed agricultural civilizations based on the happenstance of having found enough local native life suitable for exploitation.  Additionally, the planet's geographical features had a strong impact on our cultural evolution long after that.

        My point is that there's far more that needs to be 'just so' for an advanced civilization to exist.  Even with all the technical progress that had been made in our shared history, science is still very new.  Exploration, discovery and invention occurred thousands of years before modern scientific ideas ever existed.  Science is the tool of investigative discovery that was developed only after thousands of years of proto-science.  Even given a high degree of intelligence, tools and society, I do not consider science a given development.

        It is kind of interesting to imagine a world that never developed scientific concepts like skepticism and rigorous testing of hypothesis.  Can such a world exist above a certain threshold of technological achievement?  What would a society like that look like with rocketships and satellites?  (Such things would be invented and developed with the same slow methodology that ancient people used to learn metallurgy and medicine.)

        Anyway, we benefit from a huge number of easily exploitable plants and animals.  Not all life is useful to us.  If we didn't happen to have so many on the planet, we wouldn't be where we are now.  In light of this, I think it's perfectly reasonable that what we consider 'intelligent civilizations' could be quite rare indeed.

  •  I just don't get how radial velocity can work (5+ / 0-)

    I don't know - I just find the whole thing really questionable. My visualization is; here's an elephant (star). Now we're going to attach a fly (planet) to the elephant and let it circle around the planet. Now you, from 5 miles away, watch that elephant and deduce that a fly is pulling on it from measuring the movement of the elephant. Oh, and while we're at it, we've also attached 5 other flies to the elephant, all pulling the elephant in different directions, effectively cancelling out the pulling of all the other flies.

    It just makes my head hurt. And I'm a huge believer in science! But I find all this really iffy.

    Romney 2012 - Enough.... is never enough. (Ferengi Rule of Acquisition #97)

    by Fordmandalay on Mon Jul 23, 2012 at 01:14:54 PM PDT

    •  You correctly describe the problem. Maybe... (3+ / 0-)
      Recommended by:
      terrypinder, ozsea1, Apost8

      the extremes of elephant:fly for mass is a bit of a stretch. But, the concept is right. We are looking for a wave function when measuring the radial velocity. Here is an example. Look at the upper left for a graph. Notice the wobble of the star in question is on the order of 100 m/s caused by that 'fly of a planet'.

      Data for this example shows the star a little larger than our Sun (1.12x). The planet is about the mass of Jupiter (1.009x). It orbits in less than 3 days (2.7566 days). Our Jupiter orbits in 4,332 days.

      This planet is VERY close to the star and causes a lot of wobble compared to our Jupiter's effect on the Sun. Hence, a more easily observed radial velocity.

      Does that help with your question?

      Universe started with a Big Bang. It's big, getting bigger, and mostly dark.

      by jim in IA on Mon Jul 23, 2012 at 02:04:47 PM PDT

      [ Parent ]

    •  try this: (3+ / 0-)
      Recommended by:
      terrypinder, TX Freethinker, wxorknot

      Take a large heavy ball and throw it across the yard or down the street, and watch how it moves.  

      Next, attach a string, let's say two feet long, to the large ball, using duct tape.  To the other end of the string, attach a small relatively light ball, such as a 1-inch diameter ball of the type that is especially bouncy (we used to call them "superballs").

      Now throw your large ball the same way and observe how it moves with the small ball attached with the string.

      You'll notice that the motion of the large ball is substantially different as the small ball adds mass (weight) to the system and swings around the large ball as they fly through the air.

      What you've just seen, is the effect of a smaller object at a distance from a larger one.  The string that ties them together is equivalent to the gravity that keeps a planet in orbit around a star.  

      The entire system moves around its center of gravity, which is determined by the mass of all the objects in the system.  By analogy, a bus driver notices that a bus handles differently depending on where the passengers are sitting: if most of them are on one side, the bus leans toward that side because its center of gravity is offset to that side.  

      We know from Newtonian physics (which is still perfectly valid so long as we're not dealing with objects moving at speeds close to the speed of light, or with very tiny objects on the subatomic scale), how a star should appear when there are planets orbiting it, and when there are not planets orbiting it.  Without planets, it appears steady; with planets, it appears to move back and forth slightly due to the motion of the center of gravity of the entire system.  

      By analogy, if you watch a bus go around a corner, you can estimate the percentage of passengers sitting on each side of the aisle, by watching how the bus moves.  

      We can estimate the mass of a star from other observations of it, and from this plus its motion, we can estimate the mass of the planets orbiting it.  

      All of these things can be estimated within fairly small windows of variation.  This enables us to make calculations of the approximate sizes of the planets orbiting the star.  

      And this is one of the really cool things about science: if you know a few things very well, you can make informed guesses about other things you don't know yet, and you can test your guesses and refine them until you get them right.  

      Does this make sense?  

      "Minus two votes for the Democrat" equals "plus one vote for the Republican." Arithmetic doesn't care about your feelings.

      by G2geek on Mon Jul 23, 2012 at 02:48:02 PM PDT

      [ Parent ]

      •  So, in effect, it's like a jello-mould on a table (2+ / 0-)
        Recommended by:
        terrypinder, ozsea1

        Undisturbed, it sits still - but if you bounce small balls (planets) on the table, the jello shakes with vibration (gravity) waves. Okay, my mind can get around that.

        Romney 2012 - Enough.... is never enough. (Ferengi Rule of Acquisition #97)

        by Fordmandalay on Mon Jul 23, 2012 at 03:02:26 PM PDT

        [ Parent ]

        •  nice analogy! (1+ / 0-)
          Recommended by:

          Yeah, that works as an illustration.  The actual physics are different, but the analogy is nice.  

          A slightly better version might be:

          You have a bowl of water in the middle of a slightly wobbly round table.  You have a model railroad track circling the table, with a model train running on it.  The weight of the train as it circles the table causes the table to wobble slightly.  

          If you watch the water in the bowl, you'll notice that it sloshes around in the bowl just a very little bit as the train orbits the table.  

          See, one doesn't need to understand the complex math behind these things, in order to come up with analogies that at least make it possible to understand the general ideas.  This is something we need to know: core science literacy is accessible to everyone, even people without the math background.  

          "Minus two votes for the Democrat" equals "plus one vote for the Republican." Arithmetic doesn't care about your feelings.

          by G2geek on Mon Jul 23, 2012 at 03:26:20 PM PDT

          [ Parent ]

        •  Or a blancmange if you prefer Monty Python (2+ / 0-)
          Recommended by:
          ozsea1, terrypinder

          but the concept is similar.

          Mitt Romney is a T-1000 sent back from the Future as a harbinger of the upcoming Robot Apocolypse.

          by mbayrob on Mon Jul 23, 2012 at 11:17:24 PM PDT

          [ Parent ]

  •  Interesting diary about one of the many ... (3+ / 0-)
    Recommended by:
    G2geek, terrypinder, Wee Mama

    planets out there. Fascinating what we are finding.

    For people with ipads, ipods, and smart phones, there is an app that catalogs the new planets. It is called Exoplanet. Every few days, it notifies you of newly found ones. You can search and plot parameters in multiple ways. You can view orbit models, the way it might eclipse the start, etc. Well worth a look.

    There is also the online version for your desktop computer.

    The Exoplanet Data Explorer is an interactive table and plotter for exploring and displaying data from the Exoplanet Orbit Database. The Exoplanet Orbit Database is a carefully constructed compilation of quality, spectroscopic orbital parameters of exoplanets orbiting normal stars from the peer-reviewed literature, and updates the Catalog of nearby exoplanets.

    Universe started with a Big Bang. It's big, getting bigger, and mostly dark.

    by jim in IA on Mon Jul 23, 2012 at 01:26:54 PM PDT

  •  Gliese 581g? I thought you were talking about (3+ / 0-)
    Recommended by:
    revbludge, ozsea1, terrypinder

    bots that have been infiltrating this website.  So glad to be wrong.

    God be with you, Occupiers. God IS with you.

    by Hohenzollern on Mon Jul 23, 2012 at 07:26:47 PM PDT

  •  It's exciting just to *know* (3+ / 0-)
    Recommended by:
    revbludge, ozsea1, terrypinder

    that there are planets around other stars. People have been guessing that there were for centuries, but it still wasn't actually known that they existed when I was young. (And astronomers were convinced back then that any such systems would have to be laid out exactly like ours.)

    I'm not sure I will be around to see it, but within a few decades we will probably have some chemical information about the atmospheres of some of these extrasolar planets.
    Based on the diversity we have been seeing so far, I wouldn't be surprised if it were to turn out that there is a lot more chemical diversity among "earth-like" planets that we might expect today.

  •  And Southwest is running a special... (6+ / 0-)

    ...from DFW to Gliese 581g for $129, one-way. Bags fly free.

    The only problem is the 13-year layover in orbit around Proxima Centauri...

    "When I give food to the poor, they call me a saint. When I ask why the poor have no food, they call me a communist." --Dom Helder Camara, archbishop of Recife

    by JamesGG on Mon Jul 23, 2012 at 07:39:12 PM PDT

  •  Internal dynamo? (3+ / 0-)
    Recommended by:
    revbludge, terrypinder, Wee Mama

    W/o a molten Fe core and the resultant magnetic field, wouldn't 581g be stripped of what atmosphere it might have by them thar stellar flares?

    And with that I am out of ammunition.

  •  Great diary, very well-written (2+ / 0-)
    Recommended by:
    ozsea1, terrypinder

    thanks for sharing this, it was interesting

    I am now imagining the new fitness craze of the 24th century, fat camp on Gliese 581g.

  •  Just watch this last night (1+ / 0-)
    Recommended by:

    "No man is rich enough to buy back his past." ~ Oscar Wilde

    by ozsea1 on Tue Jul 24, 2012 at 12:02:45 AM PDT

  •  It makes me sad too that we'll never (3+ / 0-)
    Recommended by:
    mkor7, terrypinder, Apost8

    see them in our life time.  Look at a star map:  100B galaxies witha 100B stars each, and we won't even get to see one of them.  And we're stuck here with the crazy bachmann's saying they are in-touch with the creator of all this and he wants us to go torment the gays because that is what is truly important.

    and their contempt for the Latin schools was applauded by Theodoric himself, who gratified their prejudices, or his own, by declaring that the child who had trembled at a rod would never dare to look upon a sword.

    by ban48 on Tue Jul 24, 2012 at 05:08:46 AM PDT

  •  I would think that (1+ / 0-)
    Recommended by:

    the chances of finding an almost dead-ringer for Earth sometime in the next 10 years would be not infinitesimal, especially if we put a little more effort into it. You would think that this would be the Great Race of the 21st Century.

    The universe may have a meaning and a purpose, but it may just specifically not include you.

    by Anne Elk on Tue Jul 24, 2012 at 08:47:26 AM PDT

  •  It is mathematically ridiculous (1+ / 0-)
    Recommended by:

    to think ours is the only star with planets circling it.

    It is mathematically ridiculous to think ours is the only star with a habitable planet circling it.

    Even given the complex set of criteria necessary for a planet to be habitable by life as we know it... it is still mathematically ridiculous to think we're it.

    G strikes me as a poor candidate for life as we know it. Life may exist but I doubt it can develop greatly under the conditions you describe.

    It is just a matter of time and technological advancement (if we don't destroy ourselves first) before we discover a truly habitable planet and eventually evidence of life elsewhere.

    What really intrigues me is if we discover different forms of life that have developed under completely foreign conditions. Perhaps methane based rather than carbon and water based. What would it be like? Would we recognize it? Would it be possible to develop ways of interaction between to completely hostile bases for life?

    Time will tell. But there are far too many galaxies and stars in the universe for us to be alone... regardless of the complexities required to develop and sustain life of any sort let along higher life forms such as ourselves.

    "Do what you can with what you have where you are." - Teddy Roosevelt

    by Andrew C White on Tue Jul 24, 2012 at 09:06:52 AM PDT

  •  Carl Sagan said it best: (1+ / 0-)
    Recommended by:
    "Somewhere, something incredible is waiting to be known."

    "Give to every other human being every right that you claim for yourself." - Robert G. Ingersoll

    by Apost8 on Tue Jul 24, 2012 at 10:38:57 AM PDT

  •  So - if there are earth like (1+ / 0-)
    Recommended by:

    planets in the vicinity, then what? What would it take to go visit? Especially now when we have an upper class that refuses to take any responsibility for any damn thing. What if they come visit us? Would they look at us and wonder wtf?

    To live a creative life, we must lose our fear of being wrong. -Joseph Chilton Pearce

    by glitterscale on Tue Jul 24, 2012 at 06:38:48 PM PDT

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