Possible earthlike planet found in the Goldilocks zone of a nearby star!

By Phil Plait | September 29, 2010 4:37 pm

Astronomers have announced the discovery of a planet with about three times the Earth’s mass orbiting the nearby red dwarf star Gliese 581. That in itself is cool news; a planet like that is very hard to detect.

But the amazing thing is that the planet’s distance from the star puts it in the Goldilocks Zone: the region where liquid water could exist on its surface!


Artist’s drawing (from 2007, before this announcement) of the planetary system of Gliese 581. Credit: ESO

First, a few things: 1) Gliese 581 is a dinky, cool red dwarf about 20 light years away. That’s pretty close as stars go; only a handful are closer. Bear in mind it’s still 200 trillion kilometers (120 trillion miles) away, and that’s still a bit of a drive.

2) The planet is one of six now known to orbit the star [that link goes to a PDF of the journal paper]. Apparently, all the planets have neat, circular orbits, so the system seems to be stable. This new planet takes 37 days to orbit the star once, and orbits at a distance about 1/6 the distance of the Earth from the Sun. As far as we know, it’s the fourth planet from its star.

3) The planets have all been found by the Doppler method: as they orbit the star, they tug on it. This causes a shift in the wavelength of emitted light from the star. The mass of the planet, its distance from the star, and the shape of the orbit all determine how the light shifts, which is how astronomers found those properties of the new planet.

OK, so that’s what we know. Now let me be clear here about stuff we can be fairly sure about.

If you’re too close to a star, it’s too hot to support liquid water. If you’re too far, it freezes. This defines a rough region from the star — the Goldilocks Zone, for obvious reasons — where liquid water can exist on the surface of a planet. This depends on the star, of course, but also on other factors like the planet’s atmosphere; Venus could have liquid water, but its super-thick atmosphere produces a runaway greenhouse effect which has heated it to 460° C (900° F). If Mars had a thick atmosphere, it might support liquid water! So the planet itself matters here too.

Gliese 581g, as the new planet is called, is in the zone where the temperature is just right. And with a mass of just three times that of the Earth, it’s unlikely to be a gas giant.

However, this does not mean the planet is habitable, or even very Earthlike. It may not even have any water on it at all. For now, we can’t know these things, so beware of any media breathlessly talking about life on this planet, or how we could live there.

There are some things we can speculate on with some solid footing. The orbital period of 37 days puts it pretty close to the star – since the star is a red dwarf, it’s cooler than the Sun, so being closer doesn’t necessarily mean you overheat. But it does mean the star exerts strong tides on the planet, which have the effect of slowing the planet’s rotation until it equals the orbital period. This has almost certainly happened to this planet, so in other words, one day on this planet = one year, and the planet always shows the same face to its star like the Moon does to the Earth.

That makes things a bit dicier for habitability. The side facing the star may get very hot, while the dark side gets very cold. If the planet has an atmosphere that gets mitigated somewhat (the hot air on the day side will flow over to the night side and vice versa, smoothing out the highs and lows in temperature), and may make the planet more clement. However, we have no clue if this planet has an atmosphere at all.

I also want to note that the mass found (3x Earth) is the minimum mass of the planet! It may be more massive, though it’s unlikely to be much more. The Doppler method doesn’t give an exact mass, only a lower limit. That’s frustrating, but that’s the way the math works out.

I’ll note that one of the other planets, Gliese 581d, orbits farther out but if it has a thick atmosphere like Venus it may also be able to support liquid water on its surface. All in all, this could be a very interesting system to study!

But perhaps the most interesting and exciting aspect of all this is what it implies. The Milky Way galaxy is composed of about 200 billion stars, and is 100,000 light years across. The fact that we found a planet that is even anything like the Earth at all orbiting another star only 20 light years away makes me extremely optimistic that earthlike planets are everywhere in our galaxy. 20 light years is practically in our lap compared to the vast size of our galaxy, so statistically speaking, it seems very likely it’s not unique. I don’t want to extrapolate from a data set of two (us and them), but if this is typical, there could be millions of such planets in the galaxy. Millions.

So we don’t know if this planet is all that much like Earth — the surface gravity may be quite high if it’s dense and small, for example, or it may not have any air, or it may have a thick atmosphere like Venus — but what it’s telling us is that smaller, lower mass planets at the right distance from their star for liquid water are almost certainly common in the galaxy.

And that’s big enough news for me.

Related posts:

Astronomers find triple super-Earths
A tiny wobble reveals a massive planet
HUGE NEWS: first possibly Earthlike extrasolar planet found!

CATEGORIZED UNDER: Astronomy, Cool stuff, Top Post

Comments (213)

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  1. Cool! And very hot on the other side.

  2. Erik

    Thanks, Phil. You always manage to bring clarity to hot topics like this, and in a way that is exciting and readable to us everyday science-loving folk. Great read.

  3. I love Gliese 581. So when do we give this star a proper name, something that sticks in the memory better than the current appellation?

    On tidal locking and the possibility for life:


    >Which leads to an intriguing thought. Any planets that circle red dwarfs may have given rise to astronomers as parochial as those on Earth. These alien observers may have concluded that only red dwarfs can support life, blessed as they are with stable planets where suns never set and seasons never disrupt the climate. Indeed, their SETI programs may ignore Sun-like stars altogether. After all, they might argue, any temperate planet orbiting such a star would lie so far out that it would rotate freely, subjecting life to a relentless cycle of light and dark. Any tilt of the axis would cause severe summers and winters, and changes in axial tilt might induce ice ages, with mighty glaciers smothering much of the globe. How on Earth could life possibly arise on such a hostile world?

    There was also that documentary narrated by Patrick Stewart (If We Had No Moon) where the Earth minus its Moon is discussed – in short, life could have existed but it would likely have remained in the oceans where temperature fluctuations aren’t so great as on land where the Earth would spend time with its poles directly facing the sun, then turning around and being subjected to total darkness, and then back again.

  4. damian

    It seems like the discoverers are much more optimistic about this planet than you are, Dr. Plait. Can you give any insight into why they are so sure this planet is habitable? Are they just trying to get headlines, or are they factoring in something you’re not… or are they just really attached to their new baby?

    “Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say, my own personal feeling is that the chances of life on this planet are 100 percent,” said Steven Vogt, a professor of astronomy and astrophysics at the University of California, Santa Cruz, during a press briefing today. “I have almost no doubt about it.”

    His colleague, Paul Butler of the Carnegie Institution of Washington, in Washington, D.C., wasn’t willing to put a number on the odds of life, though he admitted he’s optimistic.

    “It’s both an incremental and monumental discovery,” Sara Seager, an astrophysicist at the Massachusetts Institute of Technology, told SPACE.com. Incremental because the method used to find Gliese 581g already has found several planets (all super-Earths, more massive than our own world) outside their stars’ habitable zone, along with non-Earth-like planets within the habitable zone.

  5. MadScientist

    Life around a Red Dwarf? Kristine Kochanski!

  6. t-storm

    Maybe there is a crazy band of life right around the day/night terminator.
    Especially if is like the moon with a slight wobble/rock back and forth.

  7. Pete

    But how long until we know if it has any Illudium Phosdex, “the shaving cream atom”?

  8. Chief

    I’d love to put my name in the hat to take a trip there if it supports life. Imagine claiming a life span of 800 years with that orbit…

  9. I’ve just fired up my planetarium software to check out how the Sun looks from the night sky of this planet.

    It turns out the Sun is easy to find. It’s near the Pleiades, which is a good skymark. There’s a constellation that looks like two worms approaching the Pleiades from opposite sides, perhaps in order to eat it, and the Sun is second from the back in the Hyades-side worm. The very back end of the worm is Menkar. The other worm includes Atik and Menkib, among other stars.

    This could be useful information if you go visit and want to go home.

  10. CraigM

    Phil, the day you mention for this planet would be siderial day, correct? This planet, if tidally locked, would have no “solar” day.

  11. Gonçalo Aguiar

    How much time would take modern spaceships to get there?

  12. Thad

    Given that we (and by ‘we’ I mean those amazing astronomers) are detecting these planets around a common star via the Doppler method… how can we distinguish between the different Doppler effects? Perhaps there are less planets acting in a weird way? Are there many assumptions in place that allow the conclusion of a sixth planet to be drawn?

  13. Rob Miller

    So when are we sending a probe at 99% of the speed of light to go and take some pictures? (i know, i know — i’m living in a sci-fi universe of my own mind)

  14. Sweeeet how long till I’m hitting on green women?


  15. Robert Whiteman

    The data set isn’t just two. That’s just the number of “Yes”es within our data set. A better way to think of the data set would be the number of stars that we have checked for exoplanets. That’s a far more statistically significant number than just two. Let’s call that X.

    True, current detection methods don’t rule out the existence of exoplanets in the Goldilocks zone, but that just means that 2/X is a lower bound for the portion stars that have such planets.

  16. sherifffruitfly

    “The Milky Way galaxy is composed of about 200 billion stars, and is 100,000 light years across. The fact that we found a planet that is even anything like the Earth at all orbiting another star only 20 light years away makes me extremely optimistic that earthlike planets are everywhere in our galaxy.”

    Look ma! I got a heads on my first coin flip! I bet I’ll get LOTS of heads now!


  17. Charlie Foxtrot

    Also is there any certainty (probability?) that this planet has a strong magnetic field? Wouldn’t it be an irradiated wasteland otherwise?

  18. 24601

    if it’s 3x the mass of earth, would that mean its gravity at the surface is also 3Gs? If we visit there, we may need the power suits from Avatar.

  19. Len

    There are no modern spaceships. If we could build one, it would take many 100’s of years to get there!

  20. John O'Meara

    It should pbe pointed out that this measurement took 10 *years* with HIRES on Keck (an instrument I know well, having written the bulk of my thesis using HIRES data). Paul Butler should get extra credit tenacity points on this one.

  21. Mike

    Not necessarily, 24601. The surface gravity would depend also on the density and radius of the planet (more specifically, how far from the center of its mass would you be standing). It would have to be 3x the mass of Earth, but the same radius, for g to be 3 — and it would be pretty damn dense. I would wager that’s not the case.. take Mars for example. Its mass is 1/10th that of Earth, and its radius a little more than half. After some fancy maths that works out to roughly 40% of Earth’s gravity when standing on the surface of Mars.


  22. @24601: If the planet was the same size (volume) as earth but three times the mass, then its gravitational field would be much stronger than Earth’s, because space curvature would be more pronounced. If, though, the planet is (volume-wise) physically much bigger than Earth, then the planet’s gravitational effect would be much less for someone standing on its surface, because space curvature is less pronounced. Put another way, if Earth was 1,000,000 miles in circumference instead of 24,901 miles, but its mass was the same as it is now, you would weigh much less than what you weigh now.

    I think that’s correct. If I’m wrong, one of the more knowledgeable types here will correct me. As it should be.

  23. Shoeshine Boy

    Red sun, greater gravity……Krypton?

  24. From MSNBC:

    “‘My own personal feeling is that the chances of life on this planet are 100 percent,’ Steven Vogt, an astrophysicist at the University of California at Santa Cruz, told reporters today. ‘I have almost no doubt about it.”‘

  25. Wayne on the plains

    I’m glad to see you commenting on this so quickly, I always appreciate the BA point of view.

    As for Vogt, it seems pretty silly to say the chances of life are 100%, as you rightly point out, there are a lot of other factors (atmosphere, to say the least) that we have no idea about yet. I suspect he was just trying to grab headlines with that one, which seems pretty unprofessional for a scientist (the media can do that without his help).

  26. Brian T

    @ Gonçalo Aguiar:

    It would take us thousands of years to get there with present technology.

  27. #11 Gonçalo Aguiar

    Gliese 581 is approximately 20 light years away. A light year is approximately 5,878,499,810,000 miles (5.878 trillion miles.) 20 light years would then be about 117,569,996,200,000 miles.

    The current record for the fastest spacecraft is held by the twin Helios probes that were placed in orbit around the Sun. Both these vehicles reached top speeds of around 150,000 mph at closest approach to the Sun in their highly elliptical orbits.

    So, assuming a constant speed of 150,000 mph, it would take approximately 89,475 years for the current speed-record holder to reach the system. I recommend packing a lunch.

    Or, in my car, 206,480,499 years at highway speeds (65 mph).

    “Are we there yet?” “Are we there yet?” “Are we there yet?”

    Source for Helios probe speed info and quote:

  28. The Other Ian


    “Look ma! I got a heads on my first coin flip! I bet I’ll get LOTS of heads now!”

    The difference between the two scenarios is that when flipping coins, we already know the probability of getting heads beforehand: 0.5. Estimating a higher probability based on initial success when the probability is known is just foolish.

    In the habitable planets case, we have no idea a priori what the probability is. We don’t even have a reasonably narrow estimate of the possible range. Estimating it based on initial results isn’t going to be terribly accurate, but it’s still likely an improvement over what we already know.

  29. Mike

    Vogt also made a statement about 10 to 20% of the planets in the Milky Way having habitable planets. Also, kinda silly with no more data to back it up.

    It’s still very exciting.

  30. sherifffruitfly

    @ The Other Ian:

    “we already know the probability of getting heads beforehand”

    No, you dont. You have no idea how the coin is weighted. Maybe it’s weighted for heads, in which case you probably don’t have to wait long for the next one. Or maybe it’s weighted for tails, and you just got really lucky.

    Without knowing anything about the distribution, you don’t know jack. And one heads tells you nothing about the distribution.

  31. Tom

    Gliese 581 is a variable star, a BY Draconis variable. (It’s variable star name is HO Librae) It varies in magnitude from 10.56 to 10.58. Does anyone know how to figure out what’s the difference in the amount of radiant energy reaching ‘g’ at max and at min? Would it be significant?

  32. Messier Tidy Upper

    SUPERLUMINOUS news! (beyond mere brilliance!)

    Congrats to the team that discovered this latest marvellous new found world. :-)

  33. Messier Tidy Upper

    There’s already an awesome artwork diagram of the Gliese 581 system via facebook here :


    Well worth a look. :-)

    (Haven’t read the comments yet -sorry if this has been posted already.)

  34. Utakata

    Yay! Hopefully a planet that’s uninhabited by Republicans! <3

  35. NAW

    This is cool. But we still have a lot of “ifs” to walk through till we know anything in stone.

  36. 'neathCobaltSkies

    I wonder if this reaches the million dollar mark with Greg Laughlin’s terrestrial planet valuation formula.

  37. Bouch

    @ Pete
    Nice “Duck Dodgers” reference, but I’d be more interested if it had any Pizzazium Infinionite…

  38. Maybe if we tell all the people in Congress we can get cheap oil from the planet they’ll vote to fund a massive effort to go there.

  39. t-storm


    But I think the odds of flipping a coin 1,000,000,000 times will yield at least one more heads. Probabably easily 3 or 4. So finding something so close it’s highly improbable that the only two planets in the universe that might possibly have life are within 20 ly of each other. Even if you scrap the life part. Just the habitable zone and “not likely a gas giant” parts are pretty incredible.

  40. Phoenix Psaltery

    Ion drives are here and have been used on several unmanned craft including the asteroid explorer Hayabusa, SMART-1, Artemis, Dawn and several others. As these propulsion systems are refined, it should eventually become possible to mount a manned mission to Gliese 581g. Then, unfortunately, we’ll steal all their Unobtainium.

  41. amphiox

    Ah, Gliese 581, the star system that keeps on giving!

    I do recall that Gliese 581c and 581d were both hailed as habitable by the discoverers when first announced. If this is the same team, or involves some of the same team, then it appears they have a bit of a penchant for blowing the habitability horn.

    But seeing as c and d both still have some chance of being potentially habitable (c I think less so now than d), imagine the impetus that would have on any intelligent civilization that happens to develop on g! (And consider how close the three planets are to each other in real distance.)

    Just imagine if instead of Mars we had a 5x earth mass super-earth with a thick greenhouse atmosphere and surface oceans. We’d probably have had a manned mission land by 1975…

  42. If is has an atmosphere, chances are it will not all be frozen on the sunless side.

    Wild assumption: if this shows that the average separation between habitable planets is 20 light years, it implies that inside a sphere with a diameter of 100 light years will be 125 habitable planets.

    The back of my envelope calculation says that if it has three times Earth’s mass, and the same density of Earth, it will have a surface gravity of about 1.4g

    And remember, when an astronomer says “habitable”, they do not mean “human habitable.” They mean “it is not utterly impossible for some bizarre form of life to exist there.”

  43. Alex

    Wow. If there was life there, imagine the incredible differences in organisms between both sides of the planet. One side forever in darkness, one in the light. Evolution would have a field day there!

    Very cool news!

  44. Dcsohl

    @sherifffruitfly, there are over 50 stars within 20 ly of the solar system. That’s a small sample, to be sure.

    But still, if 1 out of a semi-random 50 stars has a Goldilocks planet, then in the other hundred billion stars in the galaxy there’s gonna be more than just a few of them, dontcha think?

  45. Joe W.

    A moon of Gliese 581 g wouldn’t be tidally locked to the star, would it? Maybe life could exist on said moon, and then it would possibly eliminate a permanent day or night.

    Either way, this is great news! Gliese 581 is probably the best exoplanet system we’ve seen, with a total of 3 planets in the habitable zone. Then again, Venus and Mars are also considered to be in our habitable zone… So you never really know what’s out there.

  46. Lavocat

    Here’s hoping that “the hunt is on” with regard to all of the stellar systems within a radius of at least 20 light years. In another few years – or less – technologies should improve to actually allow for visualization of these worlds. Imagine that!

    In no time at all, we may be finding MANY such potentially “habitable” plantets. And then what? Perhaps some Asimovian diaspora of homo sapiens into the heavens, generations en route to who knows where and what.

    If there is anyone in the world right now saying “I told you so!” it is very likely Stephen Hawking, with a huge grin upon his face.

    Thanks, Phil, you never fail to inspire. I feel like that wide-eyed little kid sitting in front of his old black-and-white, triumphantly joining in with the countdown of the Apollo program: “10, 9, 8, 7, 6, 5, 4, 3, 2, …”. Eureka!

  47. @sherifffruitfly, please stop trying to comment on probability and making a bad analogy. You are embarrassing yourself with a poor understanding of science and astronomy in particular.

    I am more intrigued by the incredibly complex analysis that must go into figuring out the motions imparted by this multiple body system. That in itself is some cool science, let alone the fact that so many planets are close to the habitable zone of this tiny star.

  48. MutantJedi

    How long to get there…

    Ignoring relativity, keeping with classic mechanics, IF you can accelerate a probe at 1/100 g, or about 0.1 m/s^2, you’ll get to about 1/3 the speed of light in about 30 years. (v=at) You’ll have travelled about 5x10e16 m, or about 1/4 of the distance to the star. (d=1/2 at^2) Over the last 1/4 leg of the trip, the probe could slow down at 1/100 g for 30 years. Over the middle 10e17 m, the probe would coast for about 30 years. (d=vt) Thus the trip would take about 90 years.

    Of course, 1/100 g is a huge acceleration. :)

  49. Nekura

    Do they know the inclination of the ecliptic relative to us? Is there any chance of a transit so that we might be able to get a spectroscopic measurement of it’s atmosphere? Or even just see any phase effects? Is there any way we can get any information on its atmosphere?

  50. ChH

    Gonçalo Aguiar Says: “How much time would take modern spaceships to get there”
    Phoenix Psaltery brings up Ion drives.

    As someone said, there are no modern spaceships, and no starships at all.

    We do have ion drives, but we don’t have a power source with anywhere near the power/mass needed to make an interstellar journey in less than thousands of years. Fission won’t cut it – we need at least fusion. Making the trip at significantly relativistic speeds (>0.5c) would require something like a Bussard Ramjet in addition to fusion, or antimatter, or some undiscovered exotic power source.

    Winchell Chung Says: “…it will have a surface gravity of about 1.4g”
    I concur – I got 1.44g assuming the same density. But … Earth is the most dense large object in our entire solar system, so I doubt the new planet would be much more dense, and it might be considerably less dense – so surface gravity definitely doesn’t preclude life.

    And Pete … the martians are moved to that planet when their plant’s ecosystem collapsed 3ga ago. That planet won’t be big enough for us as well.

  51. ChH

    One other thing – the researcher saying there’s 100% change the planet has life … that’s just stupid.

    Two questions concerning tidal locking – if this plant has a massive moon such as Earth’s, would that prevent the planet from becoming tidally locked to its star? Is it possible to even have a massive moon in a stable orbit in that solar system given how much more crowded it is than ours?

  52. t-storm

    Doing very rough calculations.
    Assuming (lots of assumptions here).

    A 1000,000 kg spaceship (it’s a long trip, it needs to be habitable) and that’s probably low.
    Accellerated to solar escape velocity by 4 Saturn V class rockets and then powered by 20 ion thrusters (thrust approx 236 millinewtons each) still only gives an accelleration of around 4.72 micronewtons).
    Without slowing down the whole trip I’m getting 5200 yrs and a final velocity of 785 km/sec.

    Short answer a light year is far, and 20.3 is super far. Remember our farthest probes launch 40 yrs ago or so are only like 10 light hours away.

    Of course depending on when they start their civilization we might be able to skip the inquisition and possibly even the civil rights movement.

  53. Nick

    Awesome. Now let’s finally get the Terrestrial Planet Finder off the ground and start getting some details about the potential habitability of the Gliese 581 system.

  54. ggremlin

    Man, the calculations to determine if this planet is habitable must make the Global Warming modeling look like child’s play.

    Everything from a surfer’s wet dream to do we need to do Oxygen mining on the dark side.

  55. amphiox

    @24601: According to the reports, they’re saying that if the planet was rocky like earth, it will have a diameter 1.2 to 1.4x earth’s, and the surface gravity will be close to 1g or only slightly higher.

    A moon of Gliese 581 g wouldn’t be tidally locked to the star, would it? Maybe life could exist on said moon, and then it would possibly eliminate a permanent day or night.

    I’ve had similar thoughts pertaining to moons of gas giants in the habitable zones, but others have pointed out that there is apparently a theoretical relationship between the expected size of large moons and the mass of the parent planet. For gas giant systems, objects from Luna sized up to Ganymede/Titan are most likely. To get an earth-sized moon you’d need a planet many times more massive than Jupiter.

    For rocky planets, I’m not sure what sizes one should expect of large moons, since they seem to arise from freak events like the Earth-Theia collision.

    But if we assume Luna-sized as a rough upper limit, well we already have a solid record of good (naked eye!) observations pertaining to the potential habitability of a Luna-sized object in a habitable zone orbit. . . .

  56. amphiox

    I may be wrong about this, but it occurs to me that when we use the rate of travel of the fastest human made space probes to calculate how long it would take to send a probe to Gliese 581, or any other extrasolar star system, the actual answer should be “never”.

    Because all those probes are in solar orbits, which presumably means that they’re traveling at below the escape velocity of the sun?

  57. Messier Tidy Upper

    @28. GumbyTheCat :

    The current record for the fastest spacecraft is held by the twin Helios probes that were placed in orbit around the Sun. Both these vehicles reached top speeds of around 150,000 mph at closest approach to the Sun in their highly elliptical orbits. So, assuming a constant speed of 150,000 mph, it would take approximately 89,475 years for the current speed-record holder to reach the system. I recommend packing a lunch.


    @10. Adrian Morgan Says:

    I’ve just fired up my planetarium software to check out how the Sun looks from the night sky of this planet.It turns out the Sun is easy to find. It’s near the Pleiades, which is a good skymark. There’s a constellation that looks like two worms approaching the Pleiades from opposite sides, perhaps in order to eat it, and the Sun is second from the back in the Hyades-side worm. The very back end of the worm is Menkar. The other worm includes Atik and Menkib, among other stars.

    Great work! Excellent comments – thanks. :-)

    @55. Nick : Seconded by me. :-)

  58. Rich


    Rather than “us and them” shouldn’t it be “here and there”? I mean, there is no reason to suppose that anyone calls that solar system home. So, there’s no “them” to speak of… unless you meant the planets I suppose.

    Just picking nits. This is still very cool news even if ultimately turns out that the planet is not habitable.

  59. Messier Tidy Upper

    @47. Joe W. Says:

    A moon of Gliese 581 g wouldn’t be tidally locked to the star, would it? Maybe life could exist on said moon, and then it would possibly eliminate a permanent day or night.

    I’m not sure but I suspect the closeness to their red dwarf sun may make moons difficult to exist in stable orbits. Note : Venus and Mercury lack moons while Pluto has three in our solar system. If moons did orbit Gl581g I’m not sure whether they’d be tidally locke dor not – that may depend ona number of things.

    Either way, this is great news! Gliese 581 is probably the best exoplanet system we’ve seen, with a total of 3 planets in the habitable zone. Then again, Venus and Mars are also considered to be in our habitable zone… So you never really know what’s out there.

    Great point. :-)

    @ 58. amphiox : Actually, there are at least five spaceprobes that are leaving the Solar system and travelling into interstellar space currently.

    1)Pioneer 10
    2) Pioneer 11
    3) Voyager I
    4) Voyager II &
    5) New Horizons

    I’m not sure why the Helios probes are faster than them & NOT flying off into interstellar space as well but I’d guess it has to do with their exact orbits which I presume are nearer the Sun.

    @56. ggremlin Says:

    Man, the calculations to determine if this planet is habitable must make the Global Warming modeling look like child’s play.

    Calculations, schmalculations what we need to do is go & see for ourselves! Send a spacecraft – or at least try with the TPF space telescope. More observations required – but the possibilities are so tantalising! :-)

    … & ‘g-gremlin’ = gremlin from G as in Gl581g? Nice online moniker. 😉

  60. Wayne on the plains

    @58 amphiox,

    Of course, any constant-speed estimate is just an order-of-magnitude exercise anyway, since any interstellar craft will either slow as it leaves the Sun’s gravity well (and speed up as it nears the destination) or more likely it will be some sort of constant drive (like the mentioned ion drives) so that it will accelerate for the first half of the trip and decelerate for the last half.

    Edited to add for 59 Messier,
    I think to make since of the Helios record you have to consider the total energy of the spacecraft (kinetic and potential). The ones you mentioned likely had less energy when they were nearer the Sun (and thus less velocity) but picked up energy from planetary flybys on the way out. That, and they never got as close to the Sun as Helios I’m sure.

  61. amphiox

    @59. Messier Tidy Upper: Thanks for the info.

    I’m not sure why the Helios probes are faster than them & NOT flying off into interstellar space as well but I’d guess it has to do with their exact orbits which I presume are nearer the Sun.

    This raises the question as to how fast exactly could we get an interstellar probe moving with current technology. If the speed of the Helios probes is due to their specific orbit around the sun, could we match that same speed with a probe going in a different direction? I am presuming that if we limit ourselves to currently available tech, any such attempt would have to rely heavily on a big gravitational slingshot around the sun to eject the probe from the solar system. . . .

    This also raises the additional issue of building a probe whose components would actually last for a period of time over 5 times the current duration of agrarian civilization and be functional on arrival.

    (Not to mention the challenging issue of ensuring that there still is a civilization around at the time of arrival to receive the return message!)

  62. Tristan

    Always wondered this, Whats the process to actually name an Exoplanet, with a proper name like what we give Sol System planets?

  63. In the first season episode of Stargate Universe “Darkness”, The Destiny, critically low on power, dropped out of FTL in a star system with a Red Dwarf at it’s center, at least one gas giant, and at least 3 terrestrial planets. One planet was described as too cold, another too hot, and the third in the Goldilocks zone.

    Physicist Lisa Park gave this speech to the camera in regards to this turn of events:

    “The odds of coming out of FTL on the outer edge of a star system…are astronomical. Throw in the fact that there are three potentially habitable planets plus a gas giant to act as a comet catcher on the outside of the system? We’re talking miraculous! So, there’s a chance now that we’re gonna live…

    Though our definition of habitable just means the surface temperature range allows for the presence of liquid water. And since the primary’s a red dwarf, the planets must have a relatively short orbital radius just to fall within that range, which means, there’s a likelihood at least one or two of them will be tidally locked: meaning one side will always be facing the star, which increases the prospect of geological instability due to tidal stresses, and I can’t stand earthquakes. I was in one when I was thirteen, and…I cut both my feet on broken glass…

    …But…it—it might be nice!”

    Very close to this possible find, all told. And this, I’m sure, comes from the influence of John Scalzi working on the program.

    If you aren’t watching it, Phil, you really should be… quickly, before Syfy cancels it.

  64. Rebecca

    It would take a couple hundred years with current technology.

  65. gss_000

    “beware of any media breathlessly talking about life on this planet, or how we could live there.:

    So far they’re not. Let’s wait for the UK press, but the US press all are describing it like this post.

  66. GaterNate

    IMForeman is right. SGU is a great show, with some of the most accurate science ever in a sci-fi show. That episode is one of my faves so far.

  67. Michael Chisnall

    Thad (#13): Given that we (and by ‘we’ I mean those amazing astronomers) are detecting these planets around a common star via the Doppler method… how can we distinguish between the different Doppler effects? Perhaps there are less planets acting in a weird way? Are there many assumptions in place that allow the conclusion of a sixth planet to be drawn?

    Yes there are assumptions in play. Despite what many media stories claim the doppler method isn’t foolproof. During the 80’s astronomers thought that they had found planets around other stars via the doppler method then they decided that actually they were seeing some sort of very weird, hitherto unknown type of pulsation instead and retracted all the claims. One of the groups involved in this, and who have benn finding their own exoplanets recently, has since retracted its retraction and, last I heard, were claiming that they had in fact found planets in the 80s after all. I also recall in the late 90s looking at one of the Butler & Marcy papers and contained evidence that some of the radial velocity variations they were seeing were due, not to planets, but to pulsations (possibly the hitherto unknown type). Many of the exoplanet claims should be taken with a pinch of salt.

  68. Jim

    I’m thinking the light and dark sides would make for a very active climate (if there’s an atmosphere). The star will heat the light side atmosphere which will rise and cool “air” from the dark side would replace it from underneath, creating strong permanent winds.

  69. Shawn

    Amazing. And, I agree with Phil’s parting thoughts that, what’s really intersting is the millions of others like it that are implied by how close it is to us. The fact that this one *could* support life, given the right conditions, means of the millions of others some must *most definitely* support life – even intelligent life! Seems like a burried lead … But I guess “Likely millions of Earth-like planets in our galaxy” is too front pagey to hold onto any credibility…

  70. I don’t want to extrapolate from a data set of two

    See, that’s why you’re the Bad Astronomer. Real astronomers are quite happy to extrapolate from sets of one or less (I recall Mike Brown estimated the population of the inner Oort Cloud from the detection of Sedna).

    Strong tidal effects are bad for satellites: that’s why Mercury and Venus don’t have any, and the giant planet satellites don’t have satellites of their own.

    trying to grab headlines with that one, which seems pretty unprofessional for a scientist

    Well, no doubt his press office is telling him it’s unprofessional not to. After all, ‘professional’ means ‘working for money’.


    So, we should be looking for porridge-based lifeforms on g? While c and d are inhabited only by bears? Or do astrobiologists just like comfy furniture?

  71. ggremlin

    @59. Messier Tidy Upper Says:

    … & ‘g-gremlin’ = gremlin from G as in Gl581g? Nice online moniker.

    Nothing so heavenly, it’s short for my old CB Handle “Green Gremlin”. My first ground vehicle was made by AMC. 😉

    As for your point, it would be nice to find out how habitable before we get there. For some interesting reasons why, read Larry Niven’s Known Space series. You really don’t what to cold cargo in his universe!

  72. Phil sounds skeptical in the article itself, but the coded headline gives away the fact that this planet is populated by talking bears living on the shores of the porridge oceans.

  73. Grand Lunar

    Pretty cool, Phil!

    I know the media will run wild with this news. Glad someone like you can tell it how it REALLY is.

    Perhaps a mission for the future along the lines of Project Daedalus is in store for stars like these. :)

  74. MattF

    Messier Tidy Upper: I’m not sure why the Helios probes are faster than them & NOT flying off into interstellar space as well but I’d guess it has to do with their exact orbits which I presume are nearer the Sun.

    Yes. Escape velocity has to do with not only the velocity of the probe, but its altitude from the Sun at that velocity. Recall the original mention of Helios’ speed (emphasis mine):

    GumbyTheCat: The current record for the fastest spacecraft is held by the twin Helios probes that were placed in orbit around the Sun. Both these vehicles reached top speeds of around 150,000 mph at closest approach to the Sun in their highly elliptical orbits.

    Escape velocity at this location is much higher than the escape velocity of the probes you mentioned as they gained velocity by stealing some of Jupiter’s momentum.

  75. Nate

    Does the calculated mass of the planet include the mass of any moons that may be orbiting it?
    I assume it would.

  76. Zucchi

    Maybe the planet has a spin-orbit resonance like Mercury, so that it does get night and day. That’d still make for a long day, but might be more livable.

  77. #61 MTU:
    The helios probes are in eccentric orbits around the Sun. They reach a speed of 150000 mph at perihelion, but far slower ( < Solar escape velocity ) at aphelion.

  78. Wow, assuming that the Wikipedia diagram of the Gliese solar system is correct:


    Planets g and d come pretty close together at times. Wouldn’t that affect g’s orbital stability?

  79. Mavrick67

    “‘My own personal feeling is that the chances of life on this planet are 100 percent,’ Steven Vogt

    Vogt makes this statement only knowing the mass of the planet and distance from it’s star, I guess he thinks there’s a 100 percent chance of life on Venus and Mars too

  80. @ #72 MattF

    Hey, I’m sure you’re correct. I was just applying some basic arithmetic to a given speed to see how long it would take to get to the planet at that speed. Any more than that and my brain starts to hurt. :)

  81. Messier Tidy Upper

    @75. Neil Haggath & #72. Matt F: That makes sense – thanks. :-)

    This link (hopefully!) :


    shows a short video of the brief local Aussie TV news item on the discovery of Gliese 581g Hmmm .. This bit from the text but also noted at the start audiovisual video too :

    “In a galaxy not too far away, astronomers have…”

    Galaxy??? Arrrggghh!! *facepalm* :-(

    Later they do correctly note its 20 light years. Now lesse, how many Galaxies are twenty light years away?+

    I suppose we should at least be grateful they didn’t say “astrologers” instead of astronomers (I have, sadly, seen *that* happen before) but still .. Sheesh. :roll:

    In brighter news theer’s already a wikipage for Gliese 581g :


    and an unofficial name of “Zarmina” after principle discoverer Vogt’s wife. I like that! :-)


    + Answer? : None, natch. Although I suppose you could consider ones that have merged with us like Omega Centauri. Kapteyn’s Star was almost certainly a member of Omega Cen once although it has travelled a *very* long way away since. About 15,790 ly to be semi-exact.(http://blogs.discovermagazine.com/badastronomy/2010/09/27/the-great-red-spot-almost-true-size/#comment-309737) Gliese 581 tho’ not-so-much.

  82. Messier Tidy Upper

    D’oh! The link to the news site doesn’t start where it should. :-(

    Scroll down the menu of video clips to the entry somewhat misleadingly titled (of course :roll: ) “A second Earth.”

  83. Messier Tidy Upper

    Nb. The link for the Omega Centauri & Kapteyn’s Star info is :


    PS. Just seen ABC TV news Lateline show which has had a much better, if still breif, report on the discovery of “Zarmina.” (Gl581g) :-)

    The ABC news website also has this report :


    Which, again, is better than the commercial TV / online news videos coverage. Not for the first or no doubt last time.


    To err is human, to really mess up requires a computer .. 😉

    I, of course, am a fallible messed up human using a computer so-ooo …

  84. @#83 Tom Hill,

    I think that planet d’s orbit is also tilted in relation to the ecliptic of the remaining part of the solar system, thus not actually interfering with the orbit of g.

  85. Mapnut

    I think Naked Bunny with a Whip is onto something (77). Who decided to call it the Goldilocks Zone? It should be the Porridge Zone!

  86. Can you write a blog post about interstellar travel? I’d like to know the current state of affairs with regards to actually going to other stars (even if it’s just probes).

    Is “warp speed” actually possible? Is there any hope of creating “wormholes”? Will we ever be able to actually travel fast enough to see a different star in a single lifetime?

  87. stogoe

    “quickly, before Syfy cancels it.”

    They just started airing season 2, of which a full 20 episodes have been ordered (if not yet filmed). There’s still time to catch it if you’re interested. It will probably even get renewed for another season (though it’s way too early to speculate). It’s more serialized than previous Stargate series, more like Ron Moore’s BSG than Stargate:TOS and Stargate:DS9. But I really like it even if none of the characters make the right decisions 100% of the time.

  88. Tim G

    The best news is soon to come (assuming no extensive budget cuts).

    Terrestrial Planet Finder
    Space Interferometry Mission

  89. ChH

    Justin Chase:
    > Is “warp speed” actually possible?

    >Is there any hope of creating “wormholes”?
    No, not that anything large enough to be useful could travel through.

    > Will we ever be able to actually travel fast enough to see a different star in a single lifetime?
    Certainly not in our lifetime.
    Theoretically, it is possible to build a fusion drive able to accelerate at 1g using interstellar hydrogen as fuel (Bussard Ramjet). You could continually accelerate to a target hundreds or even millions of light-years away, then decelerate for the 2nd half of the journey. With such a ship, due to relativistic time dilation you could get anywhere in the visible universe in a lifetime, although to an outisde observer your trip would appear to take more years than the number of lightyears traveled.
    But aside from the challenge of just building a working fusion reactor, there are other enormous challenges such as particle and e-mag radiation shielding, overcoming drag from the interstellar medium, multi-decade life-support systems etc…

  90. Mark

    What would photosynthesis be like under a red star? Red light is less energetic, is it not? So would any plant-like life be smaller and less complex than Earth plants?

  91. Jason

    And I for one salute our new Gliesian overlords!

  92. Al Viro

    @32: one magnitude == 10^(2/5) difference in luminosity, i.e. a bit
    below than e (2.512 vs. 2.718). So for small differences in magnitude
    you get a ratio of lumiosities just a bit below 1 + delta_m (1 + 0.92 delta_m,
    if you want better approximation – ln(10^(2/5)) is 0.921).

    So your 0.02mag turns into ~1.8% of difference in luminosity. Note that
    a) eccentricity alone can easily produce bigger effect – you’d need
    e ~ 0.005 or so to match it. For the Earth the difference is ~6%, IIRC.

    b) if you look in their paper on arXiv, you’ll see that they made an
    assumption of circular orbits because letting eccentricities float didn’t
    improve the fit. Which is to say, no estimates are made.

  93. Oh nos! We’ve discovered the homeworld of the Greys! Now they’ll send their whole fleet of anal-probing, cow-levitating, nuclear power plant-buzzing, difficult to photograph, spaceships to wreck havoc on our…um…our anuses, our cows, our nuclear power plants!

    Or not.

  94. Tom

    @100 Al Viro Thanks!

    The reason behind my question was that I was wondering if ‘g’ could have seasons like Earth, but due to changes in solar output instead of axial tilt or orbital eccentricity. Looks like the answer is no.

  95. Sarah

    I know the media can get out of hand with exaggerations when something like this discovery gets out there (I’m part of the dreaded media). But I don’t think it’s necessarily a bad thing in this particular case. If it gets people searching for more information about Gliese 581 and, by association, astronomical things in general, then the winner in all of this is science.

    These sorts of exciting discoveries where an imagination can have some room to flex are just the types of things that will grab and hold kids attention for the rest of their lives. And that’s totally worthwhile :)

  96. skelman

    So just to clarify, are Venus and Mars also considered inside the Goldilocks zone of our solar system? If this is true, then we must take into account the odds of those planets within the zone actually having the correct type of atmosphere and conditions for life, right? (even though we might not know what those odds are)

    So there are 3 Goldilocks zone planets in our solar system and 2 in Gliese 581? Exciting stuff, lets hope more data like this comes to light from other nearby systems.

  97. Richie

    To call it ‘earthlike’ is basically wild speculation when we only know its approximate mass and orbiting radius (as people have already said, it could easily be in the habitable zone and still end up like Venus or Mars, and we hardly know anything about the conditions of planets around red dwarf stars really) but if it generates enough public interest to get missions like the Terrestrial Planet Finder greenlit, then I say go for it..

  98. amphiox

    @107: I think Venus is at present closer than the inner edge of the sun’s habitable zone, but was within the zone when the sun was younger and less luminous a couple billion years ago. Mars is definitely within the habitable zone.

    (Actually, as I recall, at present, the inner edge of the sun’s habitable zone is 0.95AU, and earth is rather uncomfortably close to it! Earth would be more habitable than it actually is if its orbit was something like 1.1 or 1.2 AU instead of 1.0, though presumably if that had been the case, the AU itself would be defined differently!)

  99. Al Viro

    @105: definitely not like seasons, anyway; that 0.02 is about decade
    to decade [*] changes and short-term variability is about 4 times less
    than that, according to their data. The best-fit sine approximation
    for that had period a bit above 90 days, so it’s ~3 local years…

    BTW, far stronger source of seasonal variations could be a resonance
    other than 1:1; see e.g. Mercury for example of such.

    [*] Earth decades, that is. I.e. centuries for that one…

  100. ChH

    g could still have seasons, even assuming it’s tidally locked to its sun. It wouldn’t take much eccentricity to greatly vary the amount of heat energy reaching the dusk area.

    Also, even one-face bodies such as our moon do not show exactly the same face to the object they orbit – they wobble around a bit (look up Libration). For the presumably habitable band around the dusk terminator band, this wobble could result in highly variable seasonal weather.

    See the wobble here: http://www.youtube.com/watch?v=FCKmZXhVvkQ

  101. A

    Is there any solid science in this quote or is it just sensationalism?

    “An astronomer picked up a mysterious pulse of light coming from the direction of the newly discovered Earth-like planet almost two years ago, it has emerged.
    Dr Ragbir Bhathal, a scientist at the University of Western Sydney, picked up the odd signal in December 2008, long before it was announced that the star Gliese 581 has habitable planets in orbit around it.
    A member of the Australian chapter of SETI, the organisation that looks for communication from distant planets, Dr Bhathal had been sweeping the skies when he discovered a ‘suspicious’ signal from an area of the galaxy that holds the newly-discovered Gliese 581g.
    The remarkable coincidence adds another layer of mystery to the announcement last night that scientists had discovered another planet in the system: Gliese 581g – the most Earth-like planet ever found.”

    Read more: http://www.dailymail.co.uk/sciencetech/article-1316538/Gliese-581g-mystery-Scientist-spotted-mysterious-pulse-light-direction-newEarth-planet-year.html#ixzz1123Bmh6o

  102. @100: Unfortunately ChH, Bussard Ramjets have a maximum velocity, due to drag.
    Bottom line is the maximum velocity is equal to the exhaust velocity (which would be about 12%c for proton-proton fusion).

    Now, theoretically this can be avoided, IF you can figure out how to gather and fuse the interstellar medium WITHOUT SLOWING IT DOWN. Good luck.

  103. Chris Winter

    About the Sun’s habitable zone:

    Although such zones are bounded by the range of distances from a star for which liquid water can exist on a planetary surface, a planet’s actual surface temperature will be affected by additional factors such as the nature and density of its atmosphere and its surface gravity. Hence, the specific properties of a terrestrial planet, such as its size will affect its ability to exploit the habitable zone around a particular type (i.e., spectral type varying with mass) of main sequence star. In terms of orbital distance, the HZ for an Earth-size planet around a G2-type main sequence star like our Sun originally extended from around 0.95 AU to 1.37 AU (where one AU equals Earth’s average orbital distance around the Sun — Kasting et al, 1993).

    Moreover, main sequence stars brighten as they age and so a star’s HZ shifts outward as it brightens. A “continuously habitable zone” (CHZ) for a star would represent the overlap of HZs at two widely separated points of geological time. Over the past 4.6 billion years, Sol’s HZ has extended its outer limit for an Earth-size planet from 1.37 to 1.65 AU (James Kasting, 2010, page 178).

    Ref: http://www.solstation.com/habitable.htm

  104. SaD

    I think it’s such exciting news, and yet, since the chances of any of us ever seeing this planet or anything like it or the chances of any human being ever venturing beyond our close solar system neighbors is so incredibly small, it’s rather depressing! I am always saying there’s NO chance there are Vulcans out there, but it appears as though I will have to eat crow on the subject. I really think I might be the last convert to the idea of extraterrestial life. When you seriously consider the extreme improbablity of life developing on this planet alone: radiation, asteroid collision, nearest celestial neighbors exploding, planetary catastrophes, etc., etc., — just to summarize blandly and in a manner of speaking — it’s mind-blowingly amazing and really, scientifically miraculous that we’re here at all, much less that we have developed our amazing cerebral cortex. When you really think about it, everything that is is basically trying to kill you and mine your body for raw material!

    I’m sure this is a stupid question, but wouldn’t red dwarf have a different “habitable” zone than our star, for example? Wouldn’t it, or might it not be, much cooler in this zone that it would be if the planet were around a star similiar to ours? Is this discovery adjusted for that? Does it exist too close to be spared from irradiation — once again, to loosely use a term I’m sure some of the much more intellectually endowed people on this site will be able to correct me on — and isn’t it, dare I say, ridiculous to assume there’s any chance of life until we’ve established it has an atmopshere, at least? Carbon? H2O? Hell: land masses? Is it professionally irresponsible for this Vogt to have said there’s a “100% chance of life” until there IS a 100% chance?

    A lot of the people on here strike me from their writing as professionals, so I’m really curious as to everyone’s thoughts.

    Also, I wanted to say how much I appreciate presenting this information free of the excitable hyperbole. I’ve been amused all morning by statements as though it’s certain this planet has life. I knew I could rely on Phil to present it with a dose of realism and… Dare I say it… Skepticism.

  105. t-storm

    @81, i like the way you think. Also isn’t venus’ day longer than its year? That would be interesting, too.

    @93 Agreed. Goldilocks was just a thieving freeloader. And who makes porridge and then goes for a walk? Or did they go for a walk because they were all too hot and the different sizes of the bowls affected their cooling?

  106. CNN is reporting that “There is a 100% chance this planet has life” — http://news.blogs.cnn.com/2010/09/30/100-percent-chance-for-life-on-newly-found-planet/?hpt=C2

    Grrr!!!!! [head] + [keyboard]

  107. Brendan

    it would take approximately 834 499 years to reach so unless we get space crafts with warp capabilities it will never be reached

  108. ChH

    SaD, yes – they corrected for a closer habitable zone. The newly discovered planet orbits closer to its start than Mercury does to ours.
    Yes, Vogt’s 100% assertion was rediculous and irresponsible.

    To Winchell Chung, on drag – yes, that’s what I meant by “drag from interstellar medium” being an enormous challenge. I was trying to keep it simple, and contrast challenges from simple violations of the laws of physics such as traveling FTL.

  109. Don

    Once again the popular media is guilty of over hype. Eventually, the public will grow weary of one disappointment after another. Aren’t red dwarfs subject to flares. A planet in close orbit might find itself on the spit of a very intense barbecue. Goldilocks zone or not, there are too many variables to compute on this one until we have more information. As to the 100% probability of life – the public really isn’t interested in single cell organisms. They want someone with whom they can hold an intelligent conversation about the merits of Steely Dan.

  110. amphiox

    re: #117

    Careful there! Keyboards can be replaced, but you only got one head. . . .

    But CNN is just reporting verbatim what one of the researchers said. Why he would choose to say such a thing, I don’t know (though I have a few guesses).

  111. SaD

    @118 Thank you for explaining that! I’m glad to know it. I’m also glad you gave me your opnion on his statement: I’m extremely curious about how intelligent people come to regard these statements/facts/papers, etc, with the amount of times these things are accepted — by which I mean reported — by the media as straight fact without the proper research into the criteria underpinning the statements.

    It saddens me because what should be a real achievement for the research team turns into a 15-second soundbite “Possible Extraterrestial Life Found!” without a thorough explanation as to where this amazing new addition to our knowledge comes from and a greater appreciation for the science involved and the sheer, amazing magnitude of the intelligence and critical thinking necessary to make it possible.

  112. stompsfrogs

    #24. Shoeshine Boy FTW!

    Krypton! Thread over.

    Screw temperance, Phil, this is Awesome News! Capitals!

  113. el jefe

    I had no idea that the earth’s gravity could affect something so far away, fascinating.


  114. Two planets within 20 light years of each other (earth and gliese581g) really does make you think. Too bad we haven’t gotten past that whole speed of light thing. Kinda makes it hard to check this place out, but just the spark of imagination from this discovery will do for now. Thanks Dr. Plait.

  115. OK, so it’s within the right temperature range to have liquid water but that doesn’t imply anything more. I get that. But it’s the first time such a planet has been identified, and as the first planets only became visible within very recent time, it’s a pretty exciting thing all by itself.

    It reminds me of conversations I had back in college, when friends were speculating about the chances of finding intelligent life on another planet. I thought about it for a while and concluded that it would be exciting to find ANY life on another planet, even a slime mold, so long as we could be absolutely sure it hadn’t tagged along on one of our spacecraft.

    So far as we know. Earthlings are still the only living things in the Universe. As Arthur C. Clark wrote, “Two possibilities exist: Either we are alone in the Universe or we are not. Both are equally terrifying.” I would say “astonishing” in place of “terrifying.”

  116. EB

    Great article! Is this cool or what??? The fact that this discovery strongly suggests that there could be millions of Earth-like planets in our galaxy is amazing, but in one way not completely surprising…Our galaxy is huge, not to mention the estimated size of the universe…It seems very unlikely that we are the only planet with life in all of that! Can’t wait to see what we discover next!

  117. none

    @A, apparently it’s true. Bhathal did get some sort of signal from that area while doing SETI work. Best I can tell, it was a one time thing. It was reported back in May of ’09:


  118. DigitalAxis

    @96 Tim G:

    Sadly, Darwin/TPF and SIM were cancelled in the latest decadal review. There are no dedicated planet-finding missions (except they claim WFIRST will do it… but it would be looking for microlensing, which by definition is not a repeatable experiment, and gives very little information about where the planet is)

  119. Nemo

    It’s hard for me to believe that Vogt has been quoted correctly. If he has… I hate to say it, but he’s a crackpot.

  120. AyeThere

    this sounds interesting (:
    im only 13 and i stumbled upon this by accident, glad that i did.

  121. @117: Sigh…I saw that too, with the following quote:
    “The chances for life on this planet are 100 percent,” Steven Vogt, a UC professor of astronomy and astrophysics says. “I have almost no doubt about it.”

    Did they find the one guy who would make a wildly speculative statement like that? How many do you think they had to go through before they got their text-byte.?

  122. Michael Swanson

    If CNN was a person, I’d strangle him. This is why people say things like, “Oh global warming! Whatever! When I was a kid scientists said we were entering an ice age!” Then I have to correct them and say, “No. The NEWS said that. Some scientists said that some data may indicate that we could possibly see an ice age if the conditions were right — FORTY years ago!”

    Now they’ll say the same about life on other planets. “Oh, scientists said that there was definitely life on that one planet!” No, they didn’t! Stupid CNN did because ONE stupid scientist did! Do you see what you’re doing to me, CNN? You’re making me type in CAPITALS! Argh!

    That’s it! No astronomy article can be published anywhere anymore until they check with Phil!

  123. whencupcakesbite

    tacos are awesome. If the world ends, will we move to that planet? and will we still have tacos?

  124. Sarah

    “and may make the planet more clement.”

    More “Hal Clement”

  125. mike burkhart

    I was thinking how about aiming raido telescopes at the planet and see if we pick up any raido singals .Another comment said SETI might of found something it worth a followup .of corse even if we dont pick up any thing it there stilll could be intelgent life on the planet ,it could be they havent developed raido or tv yet .Humans have been on Earth for millons of years but we only have had raido for nearly a 100.

  126. stan9fos

    “The chances for life on this planet are 100 percent.”

    Sounds suspiciously like a corollary to one of Arthur C. Clarke’s laws, related to the inverse relation between a scientist stating the possibility or impossibilty of an event and its actual occurrence.

    Still, great news. I’m waiting to see a picture that shows it as a disc. Will the JWST be able to resolve something that size at 20 ly away? Will it be blue, brown & white? Some green patches maybe?

  127. womprat

    Nobody has pointed out that if this planet is tidally locked, it will not have a magnetic field. Some studies of mars reccently suggested that a magnetosphere protects the planet for solar wind. Without such protection the atmosphere would be eroded and suggests mars may have had more water early on because of this effect. If I remember correctly, solar wind would erode hydrogen from the upper atmosphere by breaking down H2O.

    In this case we may have a large, but arid rusty mars-like ball. Gliese is old, 7-11 billions years if I recall, so plenty of time for this process to strip water from this planet. However, bigger earthlike planets may simply have so much water that even 10 billion years won’t strip it all?

    I’ve always been keen to wager that water-ocean worlds outnumber planets like ours ten to one and that the majority of complex life in the universe is water-dwelling (Well it is on earth so that’s not really wrong already). Hopefully we find out in my life time.

  128. Victor Hernandez (shorty one)

    I agree man, it-s a great notice not because we can go to another planet, but for the simple thing that there’s other “good” worlds where to live.
    I have seen many people saying stupid things like “don’t make a party, there’s no life in that planet” or things like that.
    at least for me, that means the point I say at the beggining: There’s other worlds like our Earth, AND THAT’S VERY GOOD NEWS, I’m happy with that!!!!
    There’s too many questions
    time to be here?
    how to go?
    but the thing is: HOPE IS THE LAST THING THAT DIES!!!
    Hope we can go to those places “in a short future” :)
    BTW: sorry for my bad english LOL

  129. Dan

    @137 – CNN quoted a professional in the field – an expert even…

    Astronomer/Professor of Astronomy & Astrophysics
    UCO/Lick Observatory
    University of California, Santa Cruz

    Educational Background:
    A.B., Physics, U.C. Berkeley, 1972
    A.B., Astronomy, U.C. Berkeley, 1972
    M.S., Astronomy, U. of Texas at Austin, 1976
    Ph.D., Astronomy, U. of Texas at Austin, 1978

    CNN is completely right to quote what he says. He is an expert – that carries weight. If he was some guy in a trailer park in Oklahoma or some guy with a U Phoenix Astronomy degree then you would be right. But don’t blame the “evil media” for quoting an expert – in context.

    “Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say, my own personal feeling is that the chances of life on this planet are 100 percent.”

    On the other hand – he’s not an “Exobiologist” or even a biologist and the “ubiquity and propensity of life to flourish wherever it can” is really just hopeful BS based on the fact that the one planet that has been confirmed to have life on it – seems to have life all over it.

    Like he said – it’s his personal opinion. And he is entitled to it – and CNN is allowed to report his opinions and it is (IMO) ethical for them to do so.

  130. Given that the planets’ orbits are so close, and that there is a Big planet (neptune sized?) between it and its star, is it possible that the bigger one could cast shadows on the habitable one, if the geometry allows it?

  131. ChH

    philippec – even if the geometry is right, it would be seen as a transit, associated with a barely-noticable dimming of their sun. So … a bit of a penumbra / antumbra, yes, but not what you’d normally call a “shadow”.

    However – it is possible that regions near the terminator experience periodic fluctuations in the amount of light received due to libration (the wobble of a tidally locked object).

  132. Katharine

    Wake me up when you find one that doesn’t require a spacesuit to explore, physics-types, we in biology are waiting. I find the biological angle is being ignored a bit.

    I understand the glee about every new exoplanet, but I think we need to increase our standards for what we get pants-pissingly excited about.

  133. Messier Tidy Upper

    @146. philippec Says:

    Given that the planets’ orbits are so close, and that there is a Big planet (Neptune sized?) between it and its star, …

    Yes. Gliese 581 b and c are sorta Neptune sized – or at least between Neptune and Earth sized see :


    The system from the star itself (a faint M3 V red dwarf outwards) runs

    Gliese 581 b – 16 x Erath mass “Hot Neptune” or perhaps “gas dwarf” planet

  134. Messier Tidy Upper

    @146. philippec Says:

    ..a Big planet (Neptune sized?) between it and its star..

    Yes. All the planets detected so far in the Gliese 581 system are larger than our Earth ranging from just twice Earth’s mass up to 16 times Earth’s mass.

    For comparison, Neptune “weighs in” at 17 earth masses & Ouranos at 14 & with Earth being the most massive inner planet in our system we really have nothing quite like the intermediate mass range “Gas Dwarf-SuperEarth” (misleadingly misnamed methinks!) Gliesean planets in our solar system.

    The “Gliesean 581-ite” (?!) system going from the star itself (a faint M3 V red dwarf) outwards runs :

    Gliese 581 e – Innermost “SuperMercury” world 1.9 Earth mass 3.15 day orbit.

    Gliese 581 b – 16 x Earth mass “Hot Neptune” or perhaps “gas dwarf” planet 5.4 day orbit.

    Gliese 581 c – 6 x Earth mass “SuperVenus” planet or perhaps “gas dwarf”, 13 day orbit.

    Gliese 581 g – this newest found world 3~4 x Earth mass really may be a SuperEarth – maybe! 37 day orbit. (Remember what others have noted here about tidal locking and the possible FXts on it planetary magnetic field and also keep in mind that it may not be a solid surface planet but a very small “Hot Ice Ocean” or “Gas dwarf” type planet instead.)

    Gliese 581 d – 7 x Earth mass (half of Ouranos’es mass) “gas dwarf” / exo-Neptune 66 day orbit.

    Gliese 581 f – 7 x earth mass (ditto) “exo-Neptune” or “Super-Pluto” or “gas dwarf.” Orbiting at 0.758 AU the equivalentof just beyond venus’es orbit in our solar system it nevertheless has a year longer than Earth’s of 433 days. (its sun ismuch less gravity so tugs its planets much slower.)

    Note also for comparison that Mercury is at a distance of 58 million kilometres (0.387 AU) and completes an orbit in 88 days.

    Note the more likely descriptive terms I’ve chosen here.

    “Gas dwarf ” was one term that exoplanet hunter Sara Seager came up with & which suggest essentially asmaller version of Neptune / Ouranos. Gl581 b with 16 x the mass of Earth (mE) is almost certainly a Hot Neptune – a hotter version of Neptune. It would be very surprising to find it was rocky or had any solid surface – although we never really know 100% until we’ve observed it close up!

    Gl 581 d, f, & c with 7- to – 6 mE still have half the mass of Ouranos and so while we don’t know for sure, they may well be “Hot Ice worlds with thick atmospheres smothering oceans above successive layers of high pressure “Hot Ices”. That’s a guess natch based on what seems reasonable now.

    Gl 581 e -the smallest and innermost of the worlds is what I consider probably a SuperMercury. Its has twice earth’s mass so unlike Mercury it just might manage to hold onto an atmosphere – or maybe not? It may well be rocky but then it could also be the core of a Hot Jupiter that has been evapourated down to almost nothing. Its unusual and we can’t really say for sure what it is like. Ah, for an FTL ship to go there & see!

    So that’s all but “Zarmina” and that’s the mostintertingiof the lot. Itcould be three earth mass, rocky and earth-like -or it could be very different -another ocean covered “hot ice” world without a solid surface or half boiling sea half frozen ice witha thinstrip of tepid to cold liquid water round its “terminator region. We really don’t know depsite cliams tothecontrary. We can speculate -as I have but until we go there or get some serious observations – but it si all educated guesswork. I think.

  135. Messier Tidy Upper

    Argh. Now why did so much of that comment end up in italics? :-(
    Could’ve sworn it wasn’t done like that. Sigh. Corrected verison for clarity & slight expansion :


    So that’s all but “Zarmina” (Gl581g) and that’s the most interesting of the lot. It could be three earth mass, rocky and earth-like.

    It *could* really be the first candidate for an Earth-like habitable planet, “Earth’s sister” as my local rag wrongly described Gliese 581 c when that exoplanet was first discovered some years ago.

    Or it could be very different – another ocean covered “hot ice” world without a solid surface or half boiling sea half frozen ice with a thin strip of tepid to cold liquid water round its “terminator” region – having a perpetual twilight shifting as libration occurs.

    We really don’t know despite claims to the contrary.

    We can speculate – as I have here, but until we go there or get some serious observations – it is all just educated guesswork. I think.


    We know “Zarmina’s” mass – or at least approximately with a set minimum. We know it exists and what its orbit is and that its stable. We know some very bare basics. That’s all. The rest is a mixture of extrapolation, calculation and guesstimation – & throw in a good pinch of imagination too. :-)

    That said, it is still a wonderful and awe-inspiring find and I, for one, am still blown away by it. :-) 8)

    PS. I know, I know, one of these days I’ll surprise y’all and get a comment right and not in bad need of editing first time. Sometimes a second and third time too as I think of more stuff that needs adding or fixing.

    Thanks for your forebearance folks.

  136. @112: No, there is no scientific content here.
    Dr. Ragbir Bhathal says he detected a signal from the general area of the constellation Tucanae. Gliese 581 is in the constellation Libra. They are not even in the same part of the sky, their declinations differ by about fifty degrees.

  137. That’s awesome!!

  138. Brian Ellis

    Red Star? Heavy Gravity? I know exactly what planet that is. Its Cripton, the home world of Superman, lol.

  139. Michael Swanson

    @ 144 Dan

    I wasn’t saying that their reporting was unethical or that they didn’t have the right to quote one academic professional who apparently doesn’t understand what “100%” means. CNN was within their rights, but like most science reporting it was ill-informed and irresponsible.

  140. JG

    This has almost certainly happened to this planet, so in other words, one day on this planet = one year, and the planet always shows the same face to its star like the Moon does to the Earth.

    Don’t you mean that in fact the planet doesn’t have a day? If the planet’s tidally locked, you can’t measure from one dawn (or whatever) to the next: you could say the “day” is everlasting or, more sensibly, that the word “day” has no meaningful application here.

    And Brian Ellis @157 should know the correct spelling is “Krypton”. Jeez.

  141. amphiox

    @ 142 womprat

    Mars lost its thick atmosphere not only because it had no magnetic field, but also because it was small, with low gravity. The rate of atmosphere loss is a function of both the gravity of the planet and the strength of the stellar wind, as well as the rate of atmospheric replenishment by volcanism. A planet heavier than earth would have a much lower rate of atmospheric loss due to increased gravity and increased volcanism replenishing and recycling atmospheric gases. We also don’t know what the stellar wind is like for Gliese 581 (or how it has changed over time).

    Also, a tidally-locked planet is still rotating (it’s rotation has the same period as its orbit), and these planets have short orbits. A rotation period of 37 earth days isn’t that slow, all things considered (it’s only a little more than an order of magnitude slower than earth’s, after all). Plus there may be tidal flexing coming to play keeping the molten planetary interiors moving.

    So I don’t think we can conclude without further evidence all that much about whether or not this planet has a magnetic field.

  142. Brian Too

    I personally find it amazing that Doppler detection can discern the stellar movement caused by 6, count ’em, 6 planets!

  143. Brian Too

    @157. Brian Ellis,

    Cripton is perpetually at war with the Bloodites!

  144. Anchor

    Messier Tidy Upper says, “Thanks for your forebearance folks.”

    WHAT forebearance?

  145. MaDeR

    About: Vogt well, he clearly stated that is his personal opinion. Sciencists are humans too.

    Well, Greg from systemic said 33k $. Pretty nice, considering that best planet known before was worth around 160$.

    anyway, news are sure good. This is matter of time when more planets like this will be discovered closer and more researchable. I hope also it will give really good reason to start again projects similiar to TPF. Distance & mass are really as minimal data about planet as possible. Size and atmosphere would be very nice addition.

  146. scribbler

    Wow! All this fuss…

    “Life on Mars” as a headline: lest we forget!


    To put this into a different realm of thought, how about saying that of all the hundreds of exoplanets out there, this is the only ONE where the possibility of life hasn’t been basically and ubiquitously ruled out…


  147. Someone

    I also vote for naming this planet Krypton! A planet with a higher gravity orbiting a red star? Thats just to similar in my opinion not to call it Krypton.

    Now if they would just find a rocky planet in Epsilon Eridini we could name that Reach!

  148. James

    To confirm that this planet habors life, NASA should build a new space probe that would detect it.

  149. Teshi

    “A planet with a higher gravity orbiting a red star? Thats just to similar in my opinion not to call it Krypton. ”

    There are billions of these planets. Do we call them ALL Krypton?

    This is cool news. We live in interesting times.

  150. Messier Tidy Upper

    @ ^ Teshi :

    There are billions of these planets. Do we call them ALL Krypton?

    Wasn’t Krypton orbiting a red supergiant that went supernova and not a red dwarf?

    If so, there’d be far fewer than billions of cnadidate planets as red superginats and high-mass stars generallyare very rare – & short-livede and don’t support life

  151. Messier Tidy Upper

    Ack. Sorry about the typos above :-( :

    Correction :

    Wasn’t Krypton orbiting a red supergiant that went supernova and not a red dwarf? If so, there’d be far fewer than billions of candidate “Krypton” planets as red supergiants and high-mass stars generally are very rare – & short-lived and thus don’t support life.

    Superman, it seems, has some bad astronomy in it. Surprise.

    Also Krypton is, if I recall right, a noble (radioactive?) gas. A “krypton planet” literally composed of krypton would be .. interesting! 😉

    @133. Nemo Says:

    It’s hard for me to believe that Vogt has been quoted correctly. If he has… I hate to say it, but he’s a crackpot.

    Well “crackpot” is a little harsh but, yeah, that was a silly thing for Vogt to say on just the evidence provided. While the chances of life on “Zarmina” (Gliese 581 g) may – or may not – be high, the truth is that’s speculation well outside what we can say we know with any degree of confidence & he shouldn’t have said it.

  152. Messier Tidy Upper

    @86. Mavrick67 Says:

    “‘My own personal feeling is that the chances of life on this planet are 100 percent,’ Steven Vogt

    Vogt makes this statement only knowing the mass of the planet and distance from it’s star, I guess he thinks there’s a 100 percent chance of life on Venus and Mars too.

    In fairness, I gather that Mars may well be habitable if it had a bit more mass and Venus may well be habitable if it had a bit less – or a less dense atmosphere. If Venus orbited where Mars does and vice-versa then who knows we just might have had three habitable planets in our solar system.

    Indeed our own solar system very early on in its history may have had a Venus with oceans that were just starting to steam away and possibly life, a primitive Earth with early life beginning and also early but doomed life on an increasingly chilly and air-losing Mars as well.

    Even today, we still aren’t 100% sure Mars is utterly lifeless as there are subtle hints from inconclusive Viking tests and the famous nanofossils that may or may not be genuine fossils seen in martian meteorite ALH – something.

    I recently read a book by by biologist Jack Cohen and mathematician Ian Stewart titled “What Would a Martian Look like?” that argued the case that the idea of a “Habitable Zone” is rather too simplistic and possibly misleading.

  153. The Beer

    For a bunch of science minded people, you really DON’T know your history…

    Of course this planet does not have life. Hint: Perpetual day on one side, perpetual night on the other??

    All the black/white people fought the white/black people to their mutual destruction!

    It was on TV, so it must be true….according to Star Trek

    Sheesh! ;^)


  154. marvs33

    (o_0)..avatar might be possible…but when do we get there?jejeje

  155. Ioakim Petridis

    Yes, but what about Uranus?

  156. it will be fascinating if we live in this so called planet
    nice one

  157. Kevin

    “It’s life jim but not as we know it”. Science always going forward never in reverse


  158. If you’re interested in an ongoing conversation about actually getting to this system sometime in the distant future, check out this thread:


  159. Seth-89

    Hey I would be happy if we saw mad ET’s there because aliens are really awesome and the we sneak attack them and take their spaceships!

  160. Edmon Punsalan

    Good and very ineresting planet to observe.After all!This is part of Science or Astronomy.
    It is very exiting topic. I hope they will have more good news?

  161. I think that the possiblities of getting life on other planet is possible..

  162. the possiblities of getting life on other planet is 100% truue….

  163. I like Science but im 9 years Old But i think the movie 2012 IS GOING TO HAPPEN true because look at the japan.Japan is a Ruined.BUT science is a coooooooooooooooooooooooooL Subject And Fun experiements in class…..iM John Noah Jonson

  164. i didn’t have any idea about this goldilocks planet. Thanks for the info:) It’s a very interesting topic, so i want to discuss it with my NASC2 class!

    — James Ph. Kotsybar

    Swaddled in magnetosphere,
    gently rocked on an arm of our mother galaxy,
    we begin to learn from our grandmother galaxies.

    Their shining countenances
    have travelled light years to enlighten us,
    with tales of their own turbulent and chaotic youth.

    At bedtime,
    they soothe us
    with stories that seem like fairy tales.

    They tell us about Goldilocks —
    a zone of immense improbability and precision
    we’ve somehow found just right.

  166. So you telling us that a day will = 1 year seen like more trouble and problems than we already have here on earth, don’t even think about the time it take to get there.

  167. Justin Kyle A. Cordero

    WoW this is were we live if the end of the world is real or not

  168. now we are safe and ready to shift on other planet.

  169. stephyy

    now we r saved from 2012

  170. ravy

    can i ask somethings in here…..
    how can we know this new planet have the life living there?
    can we live in the this new planet or not?
    thank in advanced!

  171. bill jones

    Traveling at the speed of light is way too slow. They were talking on tv like we can travel much faster than that, but if they think we can even make a spaceship travel 180,000 miles an hour let alone 180,000 miles a second, then let’s hear how anything could even be thrusted that fast? We would be able to produce a bullet projectile that could travel that speed first. Trying to make a space ship travel the speed of light is silly to even suggest it’s possible. So 20 light years away is not obtainable. But I question if they want to tell us this crap just to justify the billions wasted in space. They can send out some space ship and let it go for 500 years and see if people make contact. But to even discuss this like hey, there MIGHT be water there makes no sense. Have the seen and vehicles 20 light years away traveling from planet to planet.
    Sure there is life maybe a trillion light years away, but we’ve done all we can do in space. The next thing is to go into space and travel around the earth in 45 minutes. But to compare that light can travel a certain speed and even think that a space ship could even possibly travel that fast, then you would have to have some rockets that could produce that much thrust. Imagine going around the equator 7 times in a second.

  172. montana

    this is so exciting but i kinda like earth were like animals earth is our habitat! :)

  173. PossibilityII

    Many scientists say Venus is not even in the habitable zone, but there is evidence that it is at least in the inner edge or very close to it..heres why: Venus does not have a normal day and night rotation!!! Venus is definately marginally close to the Sun, where the best you could ever hope for is a tropical Earth with habitable continents near the poles. With a marginal orbit where liquid water could exist, but anything wrong could make it boil and make the rocks get baked, a normal 24 hour rotation and a leaner carbon mix on the planet is critical. A 6 month long day would leave the Sun baking one spot far too long. This is why venus did not survive, and why Earth MAY still manage to survive if in Venus orbit, albeit with a modestly higher stabilized surface temperature..then of course, there is the manmade destruction of our heat sink, the trees in the Amazon. Also, it helps if the planet is carbnon poor. Venus was too carbon rich, and so as the rocks got baked, they all just started releasing carbon dioxide, a very bad thing.

  174. PossibilityII

    Also, if you change a star, the life zone changes as well. A G5 star would include Earth and Venus, but would leave Mars high and dry. Mercury would still get baked. A G9 star would probably leave Earth cold enough to be in danger of freezing, Venus would have similar amount of sunshine as Earth, and Mercury would probably still be baked at 212-300F. An F0 star would have completely fried our planet at our current position, we might survive an F5 star at current orbit, but then we would be getting Venus’ amount of sunshine, and would need to live in Canada and places like that. The ultimate advantage is that Earth has that 24 hour rotation. An M0 stars life zone would include Mercury if it is the normal size and not a giant, but not Earth or Venus. The life zone of an F0 star would go from Mars to probably as far as Jupiter, the same as an A5 star. F5 zone extends from Earth to middle of asteroid belt, Rigels life zone goes from twice as far out as Pluto all the way to four times the distance of Pluto.The smallest blue one that is 1.5 Suns diameter like SiriusA would extend from middle of asteroid belt to Saturn!

  175. PossibilityII

    I meant Sirius A’s life zone–middle of asteriod belt all the way to Saturn!! With even a tiny blue star, the heat is so concentrated that a little goes a long way.

  176. Measurements

    There is another possibility on Venus. It’s slow rotation could be a result of the runaway greenhouse effect, which creates a drag. The science magazine was right, though. Venus could have liquid, albeit warm with an Earth atmosphere, and a negative feedback loop, NOT a positive one!!!You don’t want a positive feedback loop for obvious reasons. Venus could have started out with a pure carbon dioxide atmosphere, with volcanoes belching out too much CO2, not giving enough time for the CO2 to settle in the oceans and allow the clouds from rain to try to cool things. An oxygen atmosphere was needed. Measurements in sopace actually measure Venus’ orbit to be below the boiling point of water, but with a bad positive feedback loop, it wouldn’t be stable even for Earth!!!!

  177. Rick G

    how would a planet with only one side of it ever facing its star, experience a “day”?


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