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A Transient at Proxima Centauri?

I see there’s now a Wikipedia page for BLC-1, the intriguing SETI detection made by Breakthrough Listen at the Parkes Observatory in Australia. The dataset in which the signal, found at 982 MHz, turned up comes from observations made in April and May of 2019, and it’s good to know that Breakthrough is working up two papers on the signal and subsequent analysis, given that the public face of the detection was originally in the form of a story leaked to the British newspaper The Guardian before the backup research was available.

Image: CSIRO’s Parkes radio telescope in New South Wales, Australia. Credit: Shaun Amy.

The first thing to say about BLC-1 is that the acronym stands for Breakthrough Listen Candidate 1, marking the first time a signal has made it through to actual ‘candidate’ status after five years of observations, which is itself noteworthy given the intensity of the effort.

The second thing is that this is a transient, meaning it’s short-lived, and it hasn’t repeated. That gets us into tricky territory, for the SETI effort has detected numerous transients over the years, and the lack of repetition has made confirmation of their origin difficult if not impossible. The most famous is the Wow! signal detected at Ohio State in 1977, a signal that continues to inspire research, as we’re about to see in a new paper that considers some of its more unusual aspects. But more on that within a few weeks.

The BLC-1 transient may or may not be from Proxima Centauri, which is the reason for the question mark in the title. I say that because we can’t yet rule out terrestrial interference of some kind. But there are transients and there are transients, and this one does raise the eyebrows. Back in April of last year, Breakthrough was working with the Parkes instrument to study the flare activity at Proxima Centauri, a significant issue as we consider questions of habitability on planets around red dwarf stars because flares can compromise a planetary atmosphere.

The detection of BLC-1 within the Proxima data is credited to Shane Smith, an undergraduate at Hillsdale College (Michigan) working as an intern within the Breakthrough Listen project. Smith’s claim to fame should be air-tight if BLC-1 turns out to be the real deal.

We do know that the signal is narrow in bandwidth and vanished when the instrument looked away from Proxima Centauri. It contains no sign of modulation. The signal also showed some drift in frequency, which would be consistent with a source in motion; i.e., a planet orbiting a star. The intriguing habitable zone planet Proxima b has commanded attention as being an Earth-mass planet around the nearest star, and is often mentioned as a possible target for Breakthrough Starshot probes. But even the matter of drift is unusual, as Lee Billings and Jonathan O’Callaghan point out in an article in which they interviewed Breakthrough’s Sofia Sheikh (Penn State):

…the signal “drifts,” meaning that it appears to be changing very slightly in frequency—an effect that could be due to the motion of our planet, or of a moving extraterrestrial source such as a transmitter on the surface of one of Proxima Centauri’s worlds. But the drift is the reverse of what one would naively expect for a signal originating from a world twirling around our sun’s nearest neighboring star. “We would expect the signal to be going down in frequency like a trombone,” Sheikh says. “What we see instead is like a slide whistle—the frequency goes up.”

We’ve come a long way since November of 1967, when Jocelyn Bell Burnell discovered PSR B1919+21, the first radio pulsar, which was jokingly named LGM-1 (Little Green Men 1) by its discoverers. And why not? The signal seemed tight and remarkably regular.

While SETI has become far more visible since those days, we’ve seen how nature can mimic technology, but we’ve also learned that RFI – radio frequency interference – ranging from nearby transmitters to malfunctioning electronics, can get into the mix. Parkes had its ‘peryton’ bursts not so long ago, but they were traced back to problems with a nearby microwave oven.

A note on Y Combinator Hacker News last night (thanks for the tip, Steven Ward) points out that 982.000 MHz, for example, is also the wavelength of the Intel Stratix 10 FPGA, a field programmable gate array used for prototyping application-specific integrated circuits (ASICs). Several other hardware components listed there are also operating at this wavelength, a fact that Breakthrough’s analysts will doubtless be taking into account as they go through all the options for pinning this detection to terrestrial sources of RFI.

So we come back to the issue of transients and repetition. Thus far Breakthrough has subjected the BLC-1 signal to exhaustive analysis and no RFI has yet been identified. The work continues, valuable in and of itself because if this signal does turn out to be RFI, it will provide a way to fine-tune the existing Breakthrough algorithms to filter out such signals in the future.

And if we can’t find a plausible source of RFI? That would be interesting, to say the least, and we may be left with something like the Wow! signal, an intriguing but non-repeating source. I think we can say this: If it actually turns out that BLC-1 is the signature of an alien civilization, then we’ll be tempted to throw out the Fermi paradox (‘where are they?’), but also re-calibrate all our thinking about civilizations in the galaxy. After all, wouldn’t finding one around the star closest to the Sun imply we’re going to find them in great numbers almost wherever we look?

Maybe not. Who is it who said ‘the thing about aliens is that they’re alien?’ Meanwhile, we keep an eye on Proxima Centauri to see if this thing repeats.

{ 181 comments… add one }
  • Frank December 31, 2020, 10:20

    Was it known to the public in April/May 2019 that the telescope was directed AT Proxima? That would increase the possibility of a hoax. In my opinion that could have done by a fixed, quartz equipped ballon, some km away.

    What I don’t understand: If the signal only was discovered in 10/2020 why was it done to point the telescope away in 2019? That would only make sense if the signal was instantely recognized.

  • Michael Fidler January 2, 2021, 0:05

    Here some background information on the ultra-wide bandwidth (704 to 4 032 MHz) receiver used at Parks radio telescope by Breakthrough Listen. This has a section on RFI and the sources causing them and how they plane to filter them out.


    Development of an Ultra-Wideband (UWL) Receiver System at Parkes.

    5.1. The current Parkes RFI environment.

    We have a good knowledge of the Parkes RFI environment in the bands currently used for pulsar astronomy. Although the widths of the observed bands greatly exceed the widths of bands where radio astronomy has some regulatory protection, RFI within them is generally manageable and data quality is not seriously compromised. Outside of the observed bands we have limited knowledge of the radio spectrum and transient interference. To address this problem, specifically over the band of the UWL receiver, an RFI measuring
    system covering the band 50 MHz to 6 GHz has been constructed and is being installed at Parkes this week. We will use this to make a high-sensitivity survey of the RFI spectrum and transient activity at Parkes. We aim to repeat the survey at approximately six-monthly intervals to monitor long-term trends in the RFI environment.
    Known strong RFI bands affecting the Parkes enviromnent are listed in Table 1. Column 3 gives the flux density at the telescope of the in-band signal in dB(W m−2 Hz−1). Note that these estimates do not include terrain loss (usually at least a few dB) and so are conservative. For
    satellite and other transmitters where these parameters are not easy to estimate, observed signal levels from RFI monitoring are taken; this is indicated by “obs” in the Comments column. The next column gives the RFI power received at the preamplifier input in dBm assuming an average sidelobe level of −50 dB relative to the main beam; the effective antenna gain in the far sidelobes (relative to an isotropic antenna) is about +5 dBi. Given the uncertainties in this number, we assume the same effective far sidelobe gain for all frequencies. The amplifier input power levels may be compared with the receiver noise-floor power which is about −89 dBm for Tsys = 25 K and a 4 GHz bandwidth.
    Signals can propagate over the edge of the dish directly into the feed. Given a normal primary beam taper, the feed gain at the edge of the dish is about +3 dBi. Therefore, these “spill-over” signals have very similar levels to those coming in through far sidelobes of the main beam and the levels given in Table 1 are relevant.
    Table 1: Known strong RFI bands affecting the Parkes environment.
    See attached image:


    Within the UWL band, the strongest signals are likely to be the airborne Defence radar systems and the ADS-B air-navigation system at 1090 MHz. The former is very strong but only occasionally present. The latter is strong when equipped planes are in Parkes airspace. From 2014 its use will be mandatory on all new aircraft and so it can be expected to be present much of the time. A hightemperature superconducting (HTS) filter between the feed and the preamplifier may be required. Aside from these transmissions, mobile phones used by visitors near the Observatory are likely to be the most problematic. Mobile base stations are not as strong, but are always present. Satellite transmissions are ubiquitous but are usually relatively narrow-band and do not result in non-linear response. Consequently they are relatively easy to filter out in the signal processing system. Digital television (DTV) signals are broadband (7 MHz/channel) and are the strongest continuous signals in the Parkes environment. Existing transmissions are just below the band proposed for the UWL receiver but may not be significantly attenuated by the feed response. An HTS filter between the feed and the preamplifier may be required.

    • Michael Fidler January 2, 2021, 20:39

      “We have a good knowledge of the Parkes RFI environment in the bands currently used for pulsar astronomy. Although the widths of the observed bands greatly exceed the widths of bands where radio astronomy has some regulatory protection, RFI within them is generally manageable and data quality is not seriously compromised. Outside of the observed bands we have limited knowledge of the radio spectrum and transient interference. To address this problem, specifically over the band of the UWL receiver, an RFI measuring
      system covering the band 50 MHz to 6 GHz has been constructed and is being installed at Parkes this week. We will use this to make a high-sensitivity survey of the RFI spectrum and transient activity at Parkes. We aim to repeat the survey at approximately six-monthly intervals to monitor long-term trends in the RFI environment.”

      This was written back in June 2013, they have been monitoring the RFI environment and transient activity in repeated surveys at six-monthly intervals. This should give them a complete knowledge of what interference is effecting the results of the narrowband transmission in the Proxima Centauri area. That should give them a total of 12 surveys from 2013 to 2019 and with the narrow beam signal I’m sure they are looking for any new interference. If anyone has updates on these surveys please reply.

  • Floyd Mathews January 2, 2021, 16:01

    It is now very early in the fact gathering stage, but based on the three facts that appear undisputed at present, I offer the following speculations:

    1. It was a very narrow band signal centered very precisely at 282.002 MHz. So far as we know at the present time, Nature produces only broadband signals, like the static on your car radio. Therefore I speculate the Proxima signal was probably artificial, either man-made or ETI-made. Either that, or else we just discovered this new source of a natural narrow band emission.

    2. The signal frequency drifted very slightly over time, which is entirely consistent with an extraterrestrial source such as a planet or space craft in an orbit or trajectory which is either moving away or towards us at a consistent speed. Therefore I speculate the Proxima signal source probably was not Earth based but is extraterrestrial.

    3. The Proxima signal was not modulated like AM, FM or television video/audio signals in order to carry information, but was one constant continuous, unchanging, unmodulated signal, like a single musical note or tone. Therefore it was more like an intelligent beacon simply announcing one little, but very obvious, fact such as “Hey, we are over here, tune in here if you want to chat, OK?” Or possibly a single purpose radar like a military search radar? Or like an identification beacon carried by commercial airlines or “Identify friend or foe” signals carried by military aircraft? Since we don’t have any commercial or military aircraft in the vicinity of Proxima Centauri, I speculate that it was probably an ETI signal from Proxima. Either that, or some human source which just so happened to be in a direct line of sight between Proxima and the Parkes Radio Telescope in Australia on the particular occasion of this sighting.


    • Ron S. January 2, 2021, 17:25

      1. Your first assumption is incorrect. Natural masers exist. For example:

      2. Your second assumption may be incorrect. The Earth itself is accelerating due to rotation and orbital motion, and that alone will cause “drift” of an otherwise stationary source. This acceleration may or may not have been compensate for.

      3. Your third assumption may be incorrect. With a narrow band receive filter on a modulated signal, such as AM or FM, the carrier will be detected and not the modulation. Further, modulation could be of a far lesser amplitude and therefore not detected. Further still, other types of modulation, such as polarity modulation, might not be detectable by the receiver in question.

      Be very careful when making assumptions.

  • Lucas January 4, 2021, 23:51

    Ok, here is my small input, coming from complete amateur just deeply interested in that kind of things:

    1) Nothing strange about getting something from Proxima while scrutinizing Proxima – that’s actually the only way to go. Here logic of some comments fails completely. Would it be less ‘suspicious’ to get something from there while not looking in that direction? Argument totally ad absurdum.

    2) IMO nothing particularly strange about ‘almost integer’ value of MHz. For once, it’s ‘almost’. For another – that it happens to fall into full unit of our measurement system is purely coincidental. It’s like saying daily number of detected covid cases is, let’s say, 650000, so it’s very suspicious for that number to be so ’round’. No, it isn’t. It is as much probable as any other number. We may wanna speculate about meaning of it (and likely come up with nothing, just like with exactly 650k covid cases on some particular day), but this being an argument for hoax? LOL. It’s actually opposite – alleged prankster would rather avoid such frequency just not to be exposed on that very detail. And the universe is full of far for strange accidents – let me mention only one thing: why eclipses are possible.

    3) IMHO, assuming it actually is of alien origin, also nothing really strange about it coming from nearest (or any other near) star. It definitely doesn’t have to mean life in universe is common (leading to conclusion there should be plenty of such signals coming from all sides – mmm, nope, not at all) – maybe conditions in our region of Milky Way favor life arise? Maybe it’s common locally here and rare in other regions? After all, we know for sure there is one intelligent form of life here, humans. How accidental is that? Now when I think about it I would actually expect planets with life on to be somehow ‘grouped’ rather than be evenly distributed throughout galaxy, based on some set of conditions that we may or may not be aware of.

    4) Some exciting speculations – assuming it is the real deal. It doesn’t have to be aliens from Proxima. What if there is incoming visit and they just made their last stop (i.e. using Proxima as gas station) before arriving here, let’s say 20-40 years from now? Or – and this one I really like – what if there is civilization on Proxima that is like 100-150 years beyond us in technological development and they just invented radio, that signal being their first experimental transmission? If that was the case, we’d be REALLY lucky to be 150 years ahead of them and not the other way around.

    5) All that being said, I still realize it’s probably a RFI, but oh boy what if it isn’t? After all it’s never aliens until it is.

  • ljk January 5, 2021, 0:40

    SETI: new signal excites alien hunters – here’s how we could find out if it’s real

    January 4, 2021 11.46 am EST

    The US$100m (£70m) Breakthrough Listen Initiative, founded by Russian billionaire, technology and science investor Yuri Milner and his wife Julia, has identified a mysterious radio signal that seems to come from the nearest star to the Sun – Proxima Centauri. This has generated a flood of excitement in the press and among scientists themselves. The discovery, which was reported by the Guardian but has yet to be published in a scientific journal, may be the search for extraterrestrial intelligence’s (SETI) first bona fide candidate signal. It has been dubbed Breakthrough Listen Candidate 1 or simply BLC-1.

    Although the Breakthrough Listen team are still working on the data, we know that the radio signal was detected by the Parkes telescope in Australia while it was pointing at Proxima Centauri, which is thought to be orbited by at least one habitable planet. The signal was present for the full observation, lasting several hours. It also was absent when the telescope pointed in a different direction.


  • Michael Fidler January 5, 2021, 2:42

    An interesting article by someone in the know; Anthony J. Beasley is the Director of the National Radio Astronomy Observatory. This includes the VLA, ALMA, VLBA, Next Generation VLA and the VLASS.

    What’s in that Radio Signal from Proxima Centauri?
    By Tony Beasley · January 04, 2021

    The signal (named BLC-1) was detected in one channel at 982 MHz. It drifted up slightly in frequency, (an indication that the transmitter is moving, or the electronics generating or receiving the signal are fluctuating somehow), and was only roughly localized in the general direction of Proxima Centauri.

    “At this point, there is some consensus that the signal may be some form of interference, but scientific analysis of the signals detected is underway, and publication of the results is expected in the next month or so ”

    Now something that has not been talked about so far is the signal strength of the transmission? Would the strength from a drone near the scope or a satellite on a distant slow moving orbit be that strong? How about a ghost in the machine, could it be at the level measured? The big question is how large of an antenna would be needed at Proxima Centauri, as big as the rings around Proxima c or something the size of China’s ‘Alien-Hunting’ 500 meter-wide FAST dish? When the results of the analyses of the signal from the Parkes UWL receiver are published, hopefully it will give a clearer picture of the source.

    What of all the other nearby exoplanets surveyed in this study, did they pick up a similar narrow beam signal on 982 MHz or any other narrow beam freqs? Seems very strange if only Proxima was the direction for a drone, satellite or internal ghost in the machine to be the source that was causing it…….

    • Michael Fidler January 5, 2021, 8:34

      Looking at Stellarium 0.17.0, they do have the Parkes Observatory location listed and setting it up for April 29 to May 2 puts Proxima Centauri at its highest point in the sky at midnight. One and one half hour each side of that time keeps it at a height of 57 degrees 39 minutes to over 60 degrees above the horizon for the full 3 hours. This means its was 30 to 32 degrees from the zenith, so a aircraft, drone or satellite would be circling for 3 hours centered around midnight almost directly over the Parkes Radio Telescope…….

      This would make it much more difficult to do then if the scope was pointing toward the horizon where someone could be using an aircraft or drone from miles away!!!

      • Michael Fidler January 5, 2021, 10:46

        I hope you realize what this means? The signal would of had to been sent at such a time that it would be received when the earth in our solar system was closest to Proxima Centauri. ;-}

        Let me state that a little differently, the transmission from Proxima Centauri was sent 4.25 years earlier and they knew that the day the earth was going to be in the position to receive it exactly at midnight when the earth was closet to Proxima Centauri.

        • Michael Fidler January 7, 2021, 10:17

          If and that is a big IF this is the way the galactic community introduces itself to a virgin civilizations, the date of closet encounter distance to a star of the earth in our yearly orbit around the sun, other stars with planets may also send a signal on there date of culmination at midnight. We may want to monitor these stars on those dates to see if a narrow band signal is present. Now looking at nearby planetary systems there is one that will take place tonight the 8th of January: Luyten’s Star with 4 planets and 12.2 lightyears distant.


          Habitable Planet Reality Check: The Nearby GJ 273 or Luyten’s Star.


          Now anyone with a large radio telescope and some free time on it around midnight may want to monitor it tonight for narrowband signals. This star is 5 degrees north so good radio telescope coverage in both hemisphere’s. Best of luck and more to come!

        • Michael Fidler January 7, 2021, 10:18

          Well, after checking my calculations it looks like the date may be the 12th of January for Luyten’s Star date of midnight culmination. I have been travelling and resting after a long tiresome day trip for our monthly grocery shopping so may need to check. Here is the screenshot of Stellarium for date and north latitude of
          Luyten’s Star.


    • David Vanaken January 7, 2021, 13:20

      Fmin and EIRPmin of 9.2 JyHz and 1.9 GW respectively for the particular observation.

      (EIRPmin= the minimum detectable equivalent isotropic radiated power, Fmin = minimum detectable flux
      in W/m2)


  • Frank January 5, 2021, 12:12

    That sounds frightening…
    And I don’t think they would be 150 years beyond… such a surely powerful transmission on such a relatively high frequency does not smell like a rookie

  • Floyd Mathews January 10, 2021, 22:17

    Maybe the Proximans are just boring? Humorous opinion from Scientific American:


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