≡ Menu

SETI Explores the Near-Infrared

This has been a week devoted to extraterrestrial technologies and the hope that, if they exist, we can find them. Large constructions like Dyson spheres, and associated activities like asteroid mining on the scale an advanced civilization might use to make them, all factor into the mix, and as we’ve seen, so do starships imagined in a wide variety of propulsion systems and designs. Dysonian SETI, as it is called, takes us into the realm of the hugely speculative, but hopes through sifting our abundant astronomical data to find evidence of distant engineering.

This effort is visible in projects like the Glimpsing Heat from Alien Technologies (G-HAT) SETI program, which proceeds in the capable hands of Jason Wright and colleagues Steinn Sigurðsson and Matthew Povich at Penn State (see Wright’s Glimpsing Heat from Alien Technologies essay in these pages as well as his AstroWright blog). For those wanting to follow up these ideas, an excellent introduction is the paper “Dysonian Approach to SETI: A Fruitful Middle Ground?”, which ran in JBIS in 2011 (Vol. 64, pp. 156-165). It’s not, unfortunately, available online, though the British Interplanetary Society offers a print copy of the entire back issue here.


Image: NGC 2403 in Camelopardalis. Dysonian SETI, not limited to relatively nearby stars, looks for signs of astroengineering not just in our own but in distant galaxies like this one, some ten million light years away.. Credit & Copyright: Martin Pugh.

Into the Infrared

The more conventional radio and optical SETI methods continue as well. I’ve written often in these pages about Frank Drake’s Project Ozma at the Green Bank (WV) site, and cited the classic 1959 paper “Searching for Interstellar Communications” by Giuseppe Cocconi and Philip Morrison, which more or less opened up the entire field. But equally significant is Charles Townes’ 1961 paper “Interstellar and Interplanetary Communication by Optical Masers,” which ran in Nature (Vol. 190, No. 4772, pp. 205-208), from which this quote:

We propose to examine the possibility of broadcasting an optical beam from a planet associated with a star some few or some tens of light-years away at sufficient power-levels to establish communications with the Earth. There is some chance that such broadcasts from another society approximately as advanced as we are could be adequately detected by present telescopes and spectrographs, and appropriate techniques now available for detection will be discussed. Communication between planets within our own stellar system by beams from optical masers appears a fortiori quite practical.

Townes, who died recently, built the first maser, which worked primarily in the microwave region of the spectrum. He was a major figure in the development of both maser and laser technologies, and a winner of the Nobel Prize in 1964. The field of optical SETI has not been as visible as the older radio SETI but its proponents are actively pursuing the search at sites like Lick Observatory, where the 1-meter Nickel Telescope has been equipped with a new pulse-detection system using three light detectors, an installation that allows what Frank Drake calls “…perhaps the most sensitive optical SETI search yet undertaken.”

The new instrument is called NIROSETI, which stands for near-infrared optical SETI. It promises to gather copious data by recording levels of light over time to look for patterns that might signify a distant civilization. The beauty of working at near-infrared wavelengths is that such light penetrates much farther through gas and dust than visible light, helping us widen the search to stars thousands of light years away. NIROSETI saw first light on March 15.

Unlike Dysonian SETI, optical SETI operates under the premise that an extraterrestrial civilization may be trying to communicate with us, beaming light explicitly at our Solar System. According to this news release from the SETI Institute, NIROSETI’s use of three light detectors will allow the team to separate the brief pulses of light they are looking for from false alarms of the sort that have troubled other optical SETI experiments using fewer detectors. Optical SETI ‘noise’ can consist of cosmic rays, incident starlight, muon showers and radioactive decay in the glass of the photomultiplier tubes of the detectors, all events to be screened out of the data.

Dan Werthimer, who along with Richard Treffers (UC-Berkeley) designed an earlier instrument for optical SETI, notes where NIROSETI departs from its predecessors:

“This is the first time Earthlings have looked at the universe at infrared wavelengths with nanosecond time scales. The instrument could discover new astrophysical phenomena, or perhaps answer the question of whether we are alone.”

Shelley Wright (UC-San Diego) led the development of the new instrument while at the University of Toronto, finally signing off on detectors sensitive enough to deploy on the telescope. In addition to Wright and Werthimer, the group also includes Geoff Marcy and Andrew Siemion (UC-Berkeley), Patrick Dorval and Elliot Meyer (University of Toronto) and pioneering SETI scientist Frank Drake, whose take on the investigation is determinedly optimistic:

“There is only one downside: the extraterrestrials would need to be transmitting their signals in our direction. If we get a signal from someone who’s aiming for us, it could mean there’s altruism in the universe. I like that idea. If they want to be friendly, that’s who we will find.”


Image: Skies cleared for a successful first night for NIROSETI at Lick Observatory. The ghost image is Shelley Wright, pausing for a moment during this long exposure as the rest of her team continued to test the new instrument inside the dome. Credit: UC-San Diego.

We can hope that Frank Drake’s ideas come to pass. In any event, it’s clear that the definition of SETI is evolving as we continue to explore radio, optical and Dysonian strategies. In my view, the emergence of the Dysonian approach has been a genuine boon for our investigations. It reminds us how much astronomical data we have accumulated that can now be subjected to analysis in these terms. Will evidence of the existence of an extraterrestrial civilization come, if it does come, through a radio burst, an optical signal, or the observation of an anomaly in a distant galaxy?


Comments on this entry are closed.

  • Wojciech J March 27, 2015, 19:25

    ”There is some chance that such broadcasts from another society approximately as advanced as we are”
    That is statistically improbable based on geology and evolution. A evolutionary gap of just 10 million years(which is nothing on the time scales we are talking about) would result in civilization either advanced enough that its ideas and culture would be too incomprehensible or destructive to us, or simply on the beginning of stone age. Furthermore the distance of mere ten of light years would allow the civilization to detect our biosphere easily with telescopes and either colonize or research it.
    For these reasons the idea of directed contact by such civilization most likely won’t be confirmed by such observations.Not that it isn’t worth doing them, but I wouldn’t expect results. However searching for artefacts, traces of spaceships or probes, or mega engineering projects seems a good idea.

  • Neutrino78x March 27, 2015, 21:40

    I don’t know why we would assume a ten million year gap if they are ten light-years away. That means any signal from them is only ten years old. Now if the signal were a million light-years distant then yes I would agree, we a ate separated I’m both space and time. :-o

    My question is, how sensitive isSETI currently? Could it detect the equivalent of NORAD radar or TV broadcasts? Or does it have to be an extremely high powered intentional signal? My understanding is that the latter is currently the case. If that I’d correct,I would not expect a detection for the same reason that Stephen Hawking we should not send a signal.

  • Larry Kennedy March 27, 2015, 21:57

    One thing I notice. Everyone seems to look for the unusual, when looking for ET. We find out on a regular basis that we have misunderstood what’ s happening in the Universe. Voyager, Kepler, moons being common around asteroids, we constantly get surprises. I wonder if we should examine the idea that markers of alien civilization have been common for a century. We just don’t recognize them. Just thought I’d throw that out there.

  • d.m.falk March 28, 2015, 3:36

    In my opinion, it’s less likely we’ll encounter ETI right off in the near/optical infrared, but we will encounter chlorophyll compounds that have a distinct NIR signature that us infrared landscape photographers know so very well… :)


  • Wojciech J March 28, 2015, 10:57

    “I don’t know why we would assume a ten million year gap if they are ten light-years away. That means any signal from them is only ten years old. Now if the signal were a million light-years distant then yes I would agree, we a ate separated I’m both space and time. :-o”
    The light years distance is irrelevant. A species on another planet will experience different evolutionary time frame than we did, and thus the likelihood of any other species being developed on the same level is practically nil.
    10 million years is peanuts on evolutionary level, and they could have just as well developed 100 million or 500 million years before we did. Needless to say, we wouldn’t have much to discuss about with them.

  • Alex Tolley March 28, 2015, 11:59

    If we get a signal from someone who’s aiming for us, it could mean there’s altruism in the universe. I like that idea. If they want to be friendly, that’s who we will find.

    Like online scam artists are wanting to be friendly?

    If ETI wants to attract our attention, then the signal will have to be uncompressed. But why NIR rather than radio waves, or the even more obvious (to us) visible light?

    How far away can the signal originate before the time delay makes little sense. Within 10,000 ly? One has to wonder why beaming over long periods is that much more cost effective than sending a probe to monitor planets locally. We’ve had any number of schemes suggested to minimize costs, e.g. short bursts separated by various periods of time. Most of these suggestions seem less like logical courses of action for the ETI but rather post hoc rationalizations for a new search using the technology du jour.

    Given the pace of technology development, we are already talking about star ships of the Daedalus/Icarus class, possibly even crewed, being built within a few hundred years. It is likely that small scale probes will be built by then, able to travel at small fractions of c, say 3-10% c. We could launch these cheaply and seed many target systems. They could be relatively simple devices not much more complex than today’s technology, or as sophisticated as the devices suggested by Brin in “Existence”. Alternatively telescopes might do the job. In either case, the distance to the ETI would mean a 2x distance time delay before the ETI could receive a fresh message beamed from Earth. Far more useful for the probe to communicate instead. It also ensures that we don’t give our position away during the communication session, a fear of some when discussing METI.

    If probes are the way to go, then the issues become more about how to develop technology that will work reliably for thousands of years, perhaps longer.

  • Anthony Mugan March 29, 2015, 5:59

    There is something deeply illogical about all these SETI strategies in that the immensity of time and space available for the emergence of one or more ETCs shrinks the window of opportunity for ETCs to be both present AND distant to vanishingly small probability range close to but not quite zero.
    Whilst the possibilities being searched for by SETI strategies do not have a zero probability of occurring they are extremely unlikely to pan out. By far the more probable scenarios are at that either:
    a) We have missed something fundamental in our current thinking on the origin and evolution of life or technological issues around interstellar travel and we are truly alone…and probably unlikely to survive some great filter, or…
    b) the Galaxy is already largely populated by a civilisation indistinguishable from magic and we don’t recognise it AND they choose not to be too obvious.

    It is debatabke which is less plausible, but standard SETI requires such an extremely fine tuned scenario that I am extremely sceptical of it

  • Eniac March 29, 2015, 21:44

    Anthony Mugan:

    a) We have missed something fundamental in our current thinking on the origin and evolution of life or technological issues around interstellar travel and we are truly alone

    Why would we have to have missed something? It is an excellent a priori assumption that the origin of life is an extremely unlikely occurrence. I would think we’d have missed something if this turned out not to be the case, and we didn’t find ourselves alone in the universe.

  • John March 30, 2015, 4:40

    @ Larry Kennedy. I very much tend to agree. I wonder if we are much like people sending rafts out from their island, scouring other islands for signs of life, while radio waves whizz through them, the contrails of airliners pass overhead, and highly intelligen creatures like squid and dolphins play and communicate in the waters beneath.

    I’d also like to commit some scientific heresy here: Skepticism can sometimes be overplayed, for fear of embarresment in front of ones peers, for fear of dissapointment if later evidience doesn’t support the initial conclusions. I do not think we should abandon the idea that extraordinary claims need extraordinary evidence. I do think we need to avoid getting into the habit of dismissing any and all evidence as ‘ not extraordinary enough’. That might sound rediculous, but some people can be very clingy to their preconcieved notions.

  • Anthony Mugan March 30, 2015, 10:10

    Hello Eniac
    There is something that doesn’t sit quite right with the relatively early appearance of life here on earth with the idea that it is an exceptionally rare event. Yes, yes, yes….it could be a statistical fluke…but
    Tend to agree with Larry Kennedy and John in their remarks. Still if it is reasonable to conclude that the odds favour one of the two scenarios I described above rather than ‘they exist but are far away’ we’d be better off searching for nearby signs of their presence. But there is an elephant in the room that dare not speak its name, so that isn’t going to happen in any serious way any time soon.

  • Paul March 30, 2015, 18:34

    There is something that doesn’t sit quite right with the relatively early appearance of life here on earth with the idea that it is an exceptionally rare event.

    It could be that the conditions needed for life to arise only occur briefly, when an earth-like planet is young.

    Or, it could be that when life arises early enough in a dense young star cluster, it can spread to the other systems in that cluster before the cluster disperses. If that is the case, then most planets on which life occurs could be those that are seeded in their birth clusters, not ones where life occurs originally.

    This last possibility is interesting, since it would mean there might be 10,000 or so life-bearing stellar systems in our galaxy (the ones our solar system was born with), even if life in the larger universe is vanishingly rare.

  • Eniac March 30, 2015, 20:06

    Antony Mugan:

    Given the known fact that life exists on Earth, now, it should be expected to have made its appearance somewhere between the first time physically possible and the last time reasonable given the amount of time needed for development. That would put our expectation pretty much squarely at when it actually happened, so no statistical fluke is needed, at all.

  • ljk March 31, 2015, 12:01

    Ironically if none other than the late Charles Townes had been listened to back in 1961, we could have been searching for ETI in the optical regions as well as the radio spectrum right at the start of the 1960s, increasing our chances for a detection.

    See here for the history of why Optical SETI took so long to be accepted by the mainstream SETI community in comparison to the radio searches:


    Hopefully a mere four decade gap in a galaxy ten billion years old will not have made much of a difference in terms of our chances of finding any intelligent neighbors via these methods. Nevertheless SETI needs to be funded and treated much better than it has been: A relatively few token searches now and then are not going to cut it unless we get extremely lucky.

  • ljk March 31, 2015, 15:52

    Is New Scientist making an actual case or just teasing its readers here regarding the Fast Radio Bursts? Or both?


    To quote:

    But a fast radio burst is definitely not the easiest message aliens could send. As Maura McLaughlin of West Virginia University, who was part of the first FRB discovery points out, it takes a lot of energy to make a signal that spreads across lots of frequencies, instead of just a narrow one like a radio station. And if the bursts come from outside the galaxy, they would have to be incredibly energetic to get this far.

    If the bursts actually come from inside the Milky Way, they need not be so energetic (just like a nearby flashlight can light up the ground but a distant light does not). Either way, though, it would require a lot of power. In fact, the aliens would have to be from what SETI scientists call a Kardashev Type II civilisation (see “Keeping up with the Kardashevs”).

    But maybe there’s no pattern at all, let alone one that aliens embedded. There are only 10 bursts, and they fit into just five groups. “It’s very easy to find patterns when you have small-number statistics,” says McLaughlin. “On the other hand, I don’t think you can argue with the statistics, so it is odd.”

  • Larry Kennedy March 31, 2015, 18:00

    @ ljk
    Really intriguing, of course I have to wonder if they didn’t accidently release it a day early.

  • Rob Henry April 3, 2015, 20:18

    @Paul, I think you put your point far too lightly when you wrote “It could be that the conditions needed for life to arise only occur briefly, when an earth-like planet is young” in your reply to Anthony Mugan.

    When someone uses the early appearance of life as evidence for a high Drake f(l), those conditions do not need to have disappeared quickly to invalidate their method, a strong decay in their prevalence is sufficient.

    An example of the first might be an ocean wide ‘prebiotic soup’ the could only operate for a few years after a stupendously energetic event that wound up the chemicals (a gradual one such as once previously beloved is insufficient to the task). An example of the latter are hydrothermal systems. These still exist today, but would have been far far more common just after the late heavy bombardment, and this distorts the expected probable time of origin.

    Also of note, you do not need to invoke radiopanspermia across open clusters as an alternative way of invalidation. Invoking the more mundane lithopanspermia across time is more than sufficient to destroy the ‘high f(l) inferred’ argument. We only have to allow the possibility of an origin before the Late Heavy Bombardment, then reinfection by rocks falling back each time the crust cooler sufficiently to allow life to grow again.

  • Larry Kennedy April 4, 2015, 13:03

    There seems no end of could be when talking about origins for life. We have little but varied vague guesses on the actual mechanisms. The single data point of early origin stands on it’s own, as a single data point.