Forgot your password?
typodupeerror
Australia Communications Space Science

No Intelligent Aliens Detected In Gliese 581 239

Posted by timothy
from the beam-me-sideways-this-time dept.
astroengine writes "Using an Australian very long baseline array (VLBA) of three radio antennae, the first very long baseline interferometry (VLBI) campaign has been carried out on a SETI target star: the famous Gliese 581 red dwarf. However, after 8 hours of observing the star — thought to play host to six exoplanets, two of which are in the star's 'habitable zone' — no alien signals were detected. This result isn't surprising, as the likelihood of us stumbling across intelligent aliens living in the Gliese 581 system transmitting radio is extremely slim, but it does validate VLBI as a very exciting means of using the vast amount of exoplanetary data (coming from missions such as the Kepler space telescope) for 'directed SETI' projects."
This discussion has been archived. No new comments can be posted.

No Intelligent Aliens Detected In Gliese 581

Comments Filter:
  • The fact that we haven't detected them is proof of their intelligence, no? Would YOU want to be contacted by a race thats major claim to fame (as far as they can see) is "I Love Lucy"?

    • by Cazekiel (1417893)

      It's odd how us cynical humans always conclude that life on other planets are smarter and better than we are. Who knows--maybe they're worse than us. Maybe we're way more advanced than them.

    • Re: (Score:3, Interesting)

      Yes, they would want to contact us much in the same way we'd be insanely curious if any other creature on this planet demonstrated creative story-telling.

      I'm sorry to poop on your post but that Calvin and Hobbes cartoon that inspired your reply is over 20 years old.

      • Downmodded? Why? What am I wrong about?

    • If there are space fairing races capable of FTL travel and if they are aware of us, they are terrified that a species of hyper violent savages are about to break free of their ancient battleground and bring the pain to everybody else!

  • This result isn't surprising [...] but it does validate VLBI as a very exciting means

    I'm a little confused as how a negative result validates the excitement-quotient. Or how this could even be validated in a more meaningul sense -- there's no way of checking the data. Maybe it was a false negative and there's oodles of aliens there.

    • Re:Validation? (Score:5, Informative)

      by mbone (558574) on Saturday June 02, 2012 @06:40PM (#40196597)

      This result isn't surprising [...] but it does validate VLBI as a very exciting means

      I'm a little confused as how a negative result validates the excitement-quotient. Or how this could even be validated in a more meaningul sense -- there's no way of checking the data. Maybe it was a false negative and there's oodles of aliens there.

      The biggest technical problem in radio SETI is RFI. A signal from the star in question would have a very specific Doppler shift between the VLBI antennas, different from the relative Doppler shifts from any terrestrial RFI, even spill-over from a satellite. You can still have a saturated receiver if the RFI is too strong, but that is less of problem (it's easy to detect), and VLBI really reduces the chance of a false positive to almost nil. You also don't need an actual signal to show that this technique works.

  • They might actually still be there and just be maintaining radio silence. We'll hear them eventually... when they show up in orbit around Earth.

    • by hemo_jr (1122113)

      Also, the higher the data density that any transmission has, the harder it is to distinguish from noise. And encryption will also make a transmission look like noise.

      • by macraig (621737)

        So that gibberish my wife spouts when she's pissed is really volumes of highly advanced information in disguise? Where do I get a decoder ring for that?

        • by tnk1 (899206)

          Actually, it is highly advanced information.

          The problem the only decoder for that is another female brain. That's why when your wife is pissed at you in hearing range of other women, they start putting their hands on their hips and giving you dirty looks as well.

      • by tnk1 (899206)

        Thing is, I don't think they're looking for content, but certain characteristics of the signal, such as signal strength and continuity of the signal. One sign a signal may be of intelligent origin is that it broadcasts for an extended period of time. For instance a radio station is on all day long and certainly our outgoing SETI signals were created with the intent to make it as obvious that there was a transmission going on.

        Encryption is also a possibility, but a lot of signals we get from space may not

      • by mbone (558574)

        Ah, but the advantage of VLBI is that, even if they were just putting out noise, it would cross-correlate between antennas and be detected (if strong enough).

  • ... when there isn't any at all in the direction of us.

  • Just because there are no detectable radio signals doesn't mean there is no life, it may just be pre-industrial. WWII pushed us into the modern era. Without that we may still be using megabytes or even kilobytes and leaded gas. Maybe there is a planet with a single race and less aggressive tendencies, they may develop in a different fashion, while being advanced they may not be pumping massive RF for long-enough for us to detect. Not every species is going to be or was as addicted to TV and Radio as we a
    • by RubberDogBone (851604) on Saturday June 02, 2012 @08:28PM (#40197417)

      Most life on this planet is bacteria and viruses. They don't use radio. Most of the remaining life is a higher order of some sort, but still does not use radio. You have to go very far up the tree of life to find the one little branch where we alone are the single species using radio.

      To put it another way, in the 4.5 billion year history of Earth, every other form of life that has every existed or still exists hasn't had radio. None of them had it. We do, but only for the last 120 years or so and less than that for advanced forms of radio. Averaged out, not only has essentially no life form on Earth ever had radio, it has also essentially never happened. 1 species, 120 years, out of billions of species and billions of years.

      It did. But by no means is this something that just happens in the course of life.

      • by rrohbeck (944847)

        Yeah there's only a short time between the telegraph and neutrino beams.

      • by Doc Ruby (173196)

        I don't think even humans were meaningfully intelligent until the time we started broadcasting radio. SETI isn't looking for life, it's looking for intelligence. It takes only one species, in fact only one organism, transmitting recognizable RF for SETI to find it and meet its worthwhile goal. The rest of the planet's life might be interesting in other ways, but as long as it doesn't block RF its lack of RF use of its own doesn't mean anything.

      • >To put it another way, in the 4.5 billion year history of Earth, every other form of life that has every existed or still exists hasn't had radio. None of them had it.

        That's an entirely unproven assumption. In fact many evolutionary biologists believe it's quite arrogant to assume we're the first or last technologically advanced species on the planet. 97% of all species that ever existed is extinct. We have no proof that none of them achieved technological civilizations - we don't have any proof that th

  • No radio message received does not imply there's no intelligent life there.

    Maybe they went into planet-wide radio silence as soon as they received our first transmissions 100 years old, and have spent the last century busy preparing their invasion fleet.

    In fact, they probably landed advance scouting parties on Earth to assassinate anyone who have knowledge of their #%!@#70824645[CARRIER LOST]
  • by Chemisor (97276) on Saturday June 02, 2012 @06:24PM (#40196507)

    Having no detectable radio emissions does not preclude possibility of a civilization. Our civilization's emissions are already mostly in spread-spectrum format, which is by design indistinguishable from noise unless you know the encryption key. The transmitters we do have usually do not radiate omnidirectionally; that would be wasteful. Antennas are designed to cover the intended audience and minimize leakage outside of it, which makes detecting their radiation unlikely at any appreciable distance.

    Futhermore, natural inverse square weakening of the signal makes the signal fade into the background before leaving the solar system anyway. Our TV and radio transmitters are not going to be heard outside the solar system. It is no coincidence that our satellites communicate with highly directional dishes. Directed signals are the only ones that will make it to the next star, so what SETI is really looking for is aliens who are actively broadcasting toward Earth. I don't know why they would be doing such a dumb thing, but who knows, maybe they are a not-too-intelligent life.

    • by thegarbz (1787294) on Saturday June 02, 2012 @07:07PM (#40196807)

      That's not quite true. Some of our signals are spread spectrum, but the vast majority of licensed bands are still the age old single peak and often at insane output powers. These are very easy to distinguish from background noise, and as often is the case you could simply apply a 25kHz bandwidth and pick one of a few common coding methods and listen right in. The actual use of encryption for radio communication is rare when you're looking at the entire spectrum used over a planet. Hell if you exclude WiFi and satellite TV it's incredibly rare when you look at any major city too.

      On that note satellites have pointed dishes because they are incredibly weak. They have to be, it's not like we have power stations up there powering them. When talking to a satellite we're trying to pick out a whisper from an asthmatic across a noisy room. We attempt to make our ears highly directional and filter out other conversations and he in turn cups his mouth to get his little voice that bit higher. That's not what these SETI projects are looking for. They are looking for aliens who have set up multi-Gigawatt transmitters all over their planet, just like we have. The equivalent of a rave happening somewhere else in an otherwise quiet rural town.

      Also the directionality equation incorporates both the receive and transmit paths. You could have a perfect unit gain transmitter sending power out equally in every direction and still pick it up line of sight from anywhere you want with a theoretical infinite gain receive antenna pointed in the right direction, providing there's no louder signal source in your frequency of interest in the way. VLBI which is what they are using here provides an incredibly amount of gain at the receive side. Lots of really good signal analysis from multiple dishes result in us using a theoretical dish with a size and gain that could not realistically be constructed.

      Some real geniuses came up with these designs and I'm willing to bet they know their antenna theory enough to think that it would be possible to detect a sufficiently advanced civilisation who take a similar evolutionary route that we take.

      • by XiaoMing (1574363)

        Wish I had mod points man.

      • by Chemisor (97276) on Saturday June 02, 2012 @10:04PM (#40197929)

        the vast majority of licensed bands are still the age old single peak and often at insane output powers

        I wouldn't call a few kW insane. Only the largest transmitters in the world go into the megawatt range; the vast majority are things like wifi, which are small and weak, at
        They are looking for aliens who have set up multi-Gigawatt transmitters all over their planet, just like we have.

        You obviously don't know much about transmitters. There are no multigigawatt transmitters anywhere in the world. The most powerful transmitter in the world is the Roumoules transmitter in France [wikipedia.org], which outputs 1.4MW, three orders of magnitude less than you think. It is notable that only its longwave broadcasts can be heard past 100km, because those reflect off the ionosphere. At night, the medium waves can do that too and so can be heard farther.

        Notice that most of that radiated power will be reflected from the ionosphere and won't even make it as far as Earth's orbit. But for argument's sake, let's assume a full half of the signal makes it through. The antenna is somewhat directional, though the wikipedia article does not specify the beam width. Let's be generous and say it's a cone 30 degrees wide.

        This cone will form a moving beam across the sky as the Earth rotates. A 30 degree beam will illuminate any particular star in its path for 2 hours each day. The study in the article we're discussing listened only for 8 hours, which is too short to always catch it.

        Even if the signal is not reflected from the atmosphere, it will be significantly attenuated. Let's say 1MW makes it through. Gliese 581 is 20 light years away, ~2e17m. The base of the radiated cone is 2e17*tan30=1e17. The area of the base is pi*1e17^2=3.75e34. 1MW/3.75e34m2 = 2.67e-29W/m2.

        Minimum detectable signal [wikipedia.org] with a 1kHz bandwidth is -144dBm of the 1mW reference signal. That's 4e-15W. As a dumb estimate, we can calculate that 1.5e14m2 of continuous antenna area would be necessary to receive such a signal. That's approximately equal to the cross section of the Earth.

        Of course, that's if the signal can be received at all. At low levels like that electrons in the antenna are unlikely to absorb anything at all. The ground state energy, for example, is 13eV = 2e-18J, 11 orders of magnitude lower than the signal per square meter. I find it difficult to believe that any excitation can occur here.

        • by thegarbz (1787294)

          You obviously don't know much about transmitters. There are no multigigawatt transmitters anywhere in the world.

          I know heaps about them, but gigawatt was definitely a typo :-) Megawatt is what I meant. Incidentally the Roumoules transmitter is only the most powerful in it's band. In different bands there are transmitters several times more powerful. And even in the medium wave band in Europe it's not the most powerful transmitter ever, just the most powerful currently operating. The Germans ran a few 1.8MW transmitters throughout WW2.

          The other thing is you're talking about a snapshot of our time. Things change. Austr

        • by drinkypoo (153816) <martin.espinoza@gmail.com> on Sunday June 03, 2012 @06:30AM (#40199939) Homepage Journal

          You obviously don't know much about transmitters. There are no multigigawatt transmitters anywhere in the world. The most powerful transmitter in the world is the Roumoules transmitter in France, which outputs 1.4MW

          The HAARP project [wikipedia.org] directs a 3.6 MW signal, in the 2.8â"10 MHz region of the HF (high-frequency) band, into the ionosphere. Keep trying, you'll get it eventually.

    • by downhole (831621)

      The thing that I wonder about, and have never seen any hard numbers on, is just what it would take to transmit radio signals between stars. Take our current SETI rigs and figure out exactly what a theoretical alien civilization would have to do to stand out from the background on them. I remember reading somewhere, and I wouldn't be surprised, if it would require a multi-gigawatt transmitter with a highly directional antenna pointed at Earth, essentially a transmitter more powerful than anything we had ever

  • I have three dixie cups pointed at Gliese 581 and they haven't detected any intelligent life either. I guess I have a proof of concept as well? They'd better hope that their expensive radio telescopes can somehow compete with my much lower cost solution that achieved the same lack of results.
  • I wonder if anyone can answer this, though - how far away, is that star system? I ask because we've only been using radio waves ourselves for about what, the past 150 years or so? So that means other planets looking for us would have to be less than 150 light years away* in order for them to detect our broadcasts. Basically what I'm saying is, is that doesn't listening to that star system only prove that intelligent life that used radio waves didn't exist x amount of years ago, with x being how far away the

  • A large criticism that keeps coming up is that, if they're "more advanced" than us, they might not use radio waves for transmission of data.

    But I assume no matter how advanced we as a society get, we'll continue using electricity, and the same could be presumed for other intelligent life. Transmitting power across power lines should generate SOME level of EM-spectrum signal, no? Could we detect that?

    Okay, fine. Let's say they no longer use power lines and, say, transmit power wirelessly. Could we detect tha

    • Let's turn that around... How much of our own rf emissions would be detected by some faraway listener circling another star? Seems like a long shot...
    • by mbone (558574) on Saturday June 02, 2012 @07:44PM (#40197133)

      FTA :

      From our results we place an upper limit of 7 MW Hz1 on the power output of any isotropic emitter located in the Gliese 581 system, within this frequency range.

      .

      That means they could detect a 7 megawatt carrier tone with very narrow bandwidth of 1 HZ (or a 70 MW signal spread over 10 HZ, etc.) BUT, that is isotropic power. If the ETI was using something like the DSN antennas, much less something like Arecibo, they might have a gain of 60 dB, which means we could detect a signal down in the 10 Watt range. This search has enough sensitivity that there are lots of broadcasters on Earth (weather radar and airport radars, for example), that could be detected by this survey, if there happened to be a clone of our civilization at Gliese 581.

  • After all, if they let us find them that easily, they wouldn't be very intelligent now would they?

  • the first very long baseline interferometry (VLBI) campaign has been carried out on a SETI target star:

    Here is a rare case where a Slashdot summary is better than the original article, which simply claims to be "The First" VLBI SETI, which it isn't, not by a long shot.

    This is spectral line VLBI, and I bet almost everyone who has correlated spectral line VLBI has thought "maybe this time..." they will get lucky and see an ETI signal. I know that when Demetrios Matsakis was doing ultra-narrow band spectral line searches for the US Navy in the early 1990's, we used to joke that it was "applied SETI," as it was

  • There's no intelligent life there, just "I Love Lucy" reruns and presidential campaign commercials.

  • The problem is not that we can't detect the signal. We got all the hardware. The problem is that we might be well outside the radio signal range to be detected, as radio signal can only be carried so far by its power. But the best option for accurate detection would be to place a radio monitoring hardware just outside the orbit of Pluto for that purpose.

    http://www.computing.edu.au/~bvk/astronomy/HET608/essay/ [computing.edu.au]

    • by Doc Ruby (173196)

      Radio signals carry infinitely far, given enough time. Detecting them depends on the sensitivity of the detector. We now detect signals from stars that started out 13 billion years ago, intercepting a tiny spot of power stretched thin on the surface of an expanding sphere that's about as big as our entire universe. Gliese 581 radio signals are far more powerful than that given its proximity (20 light years), unless we're looking for a single cellphone.

      And what you just said about "just outside Pluto's orbit

  • If there is life it's either not advanced enough for radio, too advanced for radio or too xenophobic to use radio for fear of being detected. Ultimately it means practically nothing that anything was detected. In truth it doesn't even prove the radio issue. They wouldn't have detected a low power undirected radio signal like are used everyday here and a solar flare could have taken out the signal for the time they were looking and it could be back on this week. Without physically going there it's impossible
  • Telepathy doesn't have radio emissions, that's why you can't 'see' any life in the Universe.

  • Perhaps that 8 hour window coincided with their sabbath.

  • If the VLBI scan had found alien intelligence, that would have validated the technique. How does failure validated it? There's no way to distinguish between "no aliens" and "bad test" in this case.

    If they're not smart enough to figure that out, would they count as "intelligent" to the aliens scanning us? I sure hope not.

What is wanted is not the will to believe, but the will to find out, which is the exact opposite. -- Bertrand Russell, "Skeptical Essays", 1928

Working...