The Great Neutrino Tsunami
    By Johannes Koelman | February 18th 2012 02:37 AM | 34 comments | Print | E-mail | Track Comments
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    February 23rd 1987 is a day indelibly imprinted on the minds of everyone interested in astrophysics. At 7:36 GMT that day, now 25 years ago, the big one hit us. There was no escape. For 13 seconds a tsunami of neutrinos, emanating from a giant star eleven billion times more distant than the sun, flooded earth. This wave of neutrinos paled the steady stream of neutrinos reaching us from the sun by a factor of more than ten thousand.

    Yet no one noticed.

    That is, until Masatoshi Koshiba and his team inspected the data from their Kamiokande II neutrino telescope. Soon it became clear that the American IMB and the Russian Baksan neutrino observatories had detected a signal with the same time stamp: 7:36 GMT.

    Three hours later astronomers observed thru their optical telescopes a new star flaring up in the Large Magellan Cloud. The star continued to increase in brightness, and despite its mind-blowing 170,000 light years distance from earth, the star quickly became visible to the human eye. A supernova explosion had heralded the birth of a neutron star. And for the very first time, humans had directly observed the ultimate armageddon: a core collapse taking place deep inside an imploding giant star. 

    It became evident that supernova neutrinos provide us with a direct view on the inside of imploding stars. Neutrinos fly from the core to the stellar surface and out into the universe, all along not noticing their environment is anywhere different from vacuum. This in contrast to the light from supernovas that constitutes a much more indirect signal. Supernova light gets emitted from the stellar surface once the energy from the core collapse reaches this surface. The very fact that supernova photons are delayed and spread out over weeks rather than seconds, is what had prevented us from observing the true nature of a supernova. 

    By mastering neutrino detection, mankind had mastered true Superman vision. With the availability of neutrino telescopes we have the capability to peek inside distant stars. Exactly twenty five years ago, an entirely new window to the universe got opened. And over the course of twenty five years, neutrino astronomy has become big business. Quite literally, in fact.

    Size Does Matter

    Since that memorable day 25 years ago, ever increasing amounts of tax money got poured into neutrino astronomy. Larger and larger neutrino telescopes were designed and build. Where the Kamiokande team at that time had available the world's largest neutrino detector weighing in at 3 kilotonnes (3 million kilogram, about 17 times the mass of the largest known animal to have ever existed), more recent detectors dwarf this figure. The latest neutrino telescope, IceCube completed a year ago, sports a gargantuan one million kilotonne detector (yes, that is six million blue whales, quite a few more than currently roam the oceans). 

    Why these enormous sizes? 

    IceCubeNeutrinos are stealth particles. They carry no electric charge and hardly interact with ordinary matter. And that is an understatement. In order to stand a chance to get a neutrino to react or even to transfer just some of its energy, you would need to line up several hundred thousand earths on the path of that neutrino. With neutrino interactions being that rare, the number of neutrino events detected from a distant source such as a supernova will be tiny and directly proportional to the detector volume. To put this into perspective, consider the neutrino counts that characterize the supernova event twenty five years ago. Every square foot of earth got penetrated by a blast of 100,000,000,000,000 neutrinos. Despite this tsunami of neutrinos flooding earth, the combined volumes of Kamiokande II, IMB and Baksan observed no more than 25 neutrinos. 

    That's a humbling figure. And poor statistics indeed. To get a clear view on star interiors, many more neutrino events need to be detected. And that means bigger detectors need to be build.

    With each doubling of detector volume leading to a doubling in the neutrino detection rate, a contagious volume fever has spread among neutrino astronomers. In 25 years time the unit in which detector volumes are measured has evolved considerably. Gone are the days that these were measured in cubic meters. Following the delivery of the IceCube neutrino telescope, the cubic kilometer provides a more convenient unit. And plans for future neutrino telescopes promise to dwarf IceCube. The most ambitious are probably the plans for the Arianna neutrino observatory, that address the conversion of a hundred cubic kilometres of the Ross ice shelf into a colossal neutrino detector.

    With IceCube operational, we seem ready for the next neutrino tsunami. However, there is a complication. For the rare neutrino events not getting overwhelmed by spurious signals, neutrino telescopes deploy a filter that allows only neutrinos to pass. This filter is provided by earth itself. In other words, in contrast to optical telescopes, neutrino telescopes look down, and peek through earth. With IceCube being located at the South Pole, the Northern hemisphere is covered. For the southern hemisphere the smaller ANTARES neutrino telescope located in the Mediteranean provides coverage. It is twenty times smaller than IceCube, but it is better than having nothing in case the next nearby supernova is again located in the southern hemisphere. And hopefully the much larger KM3NeT will soon add neutrino detection sensitivity in the Mediterranean. Not entirely coincidental, the concluding meeting of the 'KM3NeT Preparatory Phase' project will reach its verdict on February 23rd 2012, on the day 25 years after the big one.

    The Real Challenge

    With IceCube, KM3NeT and quite a few smaller neutrino telescopes, we will be getting ready for the next neutrino tsunami. The real challenge, however, will be to utilize neutrinos not only to look deep into imploding stars, but also to look deep into the mother of all explosions: the big bang. 

    Neutrinos hold the promise of providing a window that gives us views much deeper into the big bang than the window conventionally provided by photons. When the Hubble Space Telescope gives us a snapshot of a galaxy in a universe that is only 600 million years old, this feat is brought to the wider public as big news. Yet, the Hubble does not get anywhere near to exhausting the penetration depth of photons. The true capability of photons is provided by telescopes that observe at wavelengths much larger than that of visible light. The COBE, WMAP and Planck space telescopes all do so, and provide us with a view of the earliest universe accessible via photons: a universe that is only 380 thousand years old

    With the universe at earlier times being opaque to light of any wavelength, we seem to have reached the limit of how deep we can probe into our past.

    Enter the neutrino. If we find practical ways to detect ultra low energy neutrinos, we will be able to dive much deeper than ever before into the big bang. Neutrinos hold the promise of opening a window to a universe that is only two seconds old. A prospect that will cause many a cosmologist to drool.

    Yet, the technical challenges are immense, and many believe mankind might never be able to observe directly such an extremely embryonic universe. However, we should keep in mind that neutrino astronomy is 25 years young and in its very infancy. Neutrino observations have reached a stage of maturity comparable to the maturity of photon astronomy at the time when Galileo for the first time pointed a telescope at the night sky. We have gone a long way since. The step from observing the first few extragalactic neutrinos twenty five years ago to the detailed observation of the Cosmic Neutrino Background, is probably not that much larger a step than the step from Galileo's first telescope to WMAP.

    Wait a second... is this it? Are you kiddin'? How can anyone these days have the guts to write a whole article on neutrinos without a single reference to superluminal speeds? Heresy!

    OK, ok... let me introduce you to a well kept secret: rumor has it that superluminal neutrinos were observed already 25 years ago. Yes, that's right: we are talking here about superluminal supernova neutrinos.

    Faster Than Light: So 1980's!

    Google for 'SN1987A', and you will find lots of articles on the supernova neutrinos detected 25 years ago. Most of these articles will mention the three experiments discussed above: Kamiokande II, IMB, and Baksan. However, a fourth neutrino detector also measured a signal from the direction of the Large Magellan Cloud: the LSD detector operated by a French-Italian team. LSD saw five neutrino events. Strangely enough, this happened five hours before the other three detectors signaled supernova neutrinos. Already in 1998 (way before the 2011 hype!) this observation got attributed to neutrinos reaching superluminal speeds.
    [Note to self: must utilize this observation to conform title of blogpost to de-facto Science 2.0 pagehit-optimization standard: "WHAT SCIENTISTS DON'T WANT YOU TO KNOW: TSUNAMI OF FASTER THAN LIGHT NEUTRINOS DETECTED 25 YEARS AGO?"]

    Following the LSD announcement, the Kamiokande, IMB and Baksan teams all scrutinized their data recorded at the time when the LSD detector signaled the early events. None of them could identify anything worth reporting. Now, 25 years later and following the 2011 Gran Sasso neutrino speed anomaly, the enigma hasn't disappeared. The question "Why did no other neutrino observatory than LSD detect early neutrinos?" hasn't gone away. By now, a critical observer might see a trend emerging. Only when the experiment takes place in North Italy (LSD 1987, Gran Sasso 2011), neutrinos running ahead of the pack get observed. Could it be that a wormhole is positioned over North Italy? Or are those Italians just poor timekeepers? Are superluminal neutrinos there when no Italian looks?
      [Note to self: insert obligatory joke about superluminal 'pizza neutrinos' constituting a fourth  neutrino flavor] 

    Strange animals, these neutrinos. Is it their Italian name? For sure those 'little neutral ones' provide us with lots of interesting enigmas.



    If only 25 neutrinos were detect, how do you know that :

    "Every square foot of earth got penetrated by a blast of 100,000,000,000,000 neutrinos" ?

    Johannes Koelman
    The quoted figure follows directly by combining the gravitational energy release due to the stellar collapse with a) the fraction of that energy that gets released into relativistic neutrinos (99%), and b) the distance between earth and the collapsing star. An independent verification follows from the number of events detected and the detection efficiency (fraction of events that get noticed).
    25 years since the last neutrino tsunami. How long will we have to wait till the next? Will these giant telescopes that we constructed at great cost still be there when we get flooded again by neutrinos from outer space?

    Johannes Koelman
    We don't know. The next one could reach us tomorrow, but it could also be that this century we don't witness any further nearby supernovas. Our best estimate tells us that every given year there is a 2% likelihood of a supernova within our Milky Way.
    Is the Grand Sasso deviation somehow compatible with the 5 hour difference for the LSD detector? A quick back-of-the-envelope calculation says no: a .002% deviation in 170,000 years would be about 5 years, not 5 hours. If not proportional, then what is the relationship? Now, a theory which provided an answer to both events would be interesting!

    Johannes Koelman
    To render the Gran Sasso data compatible with the SN1987a data requires a contorted model. Superluminal velocities strongly dependent on energies have been hypothesized. However, the fact that the neutrinos detected by Kamiokande II, IMB and Baksan had different energies and all arrived within a narrow time interval of 13 seconds puts very strong constraints on such dispersion effects.
    I'm glad you included LSD, 2 things.

    What are the odds of LSD detecting 5 neutrinos on the same day the other detectors lit up like christmas trees (well for neutrinos detectors), and it not being related?

    Second, Sascha has a hypothesis (good or bad, your choice), but it would seem the LSD neutrinos got a 5 some hour head start, but ended up at the low end of neutrino energy, right in the wheelhouse of LSD, but lower than the other detectors range(is this correct, I know the others detect higher energy neutrinos, does that make them less sensitive to low energy neutrions?).

    To me it seems to unlikely to be coincidence.
    Never is a long time.
    Sure, but until someone explains the time difference it will remain a curiosity. According to Johannes there is no theoretical explanation. To me the LSD results seem quite more relevant than the recent Gran Sasso experiments, where the measurements have to be so precise that any unknown source of systematic errors might be responsible of the time differences.

    A time difference of 5 hours is undeniable, unlikely to come from systematic error, and unexplained; therefore the answer is likely to teach us something about the universe. Even if it just that some of the neutrinos reflected off an object at 2.5 light-hours from the supernova, that would be a new phenomenon!

    Sascha has an explanation.
    Never is a long time.
    How does Sascha's magical initial jumps explain the LSD data? That must be a giant (billions of miles) initial jump!

    Yep, 5 light hours worth, but then it's also being power by a core collapse supernova.

    Oh, and I wouldn't blame Sascha, I mentioned the LSD data to him and he brushed it off.
    Never is a long time.
    As anoymous says above, I meant an explanation for the 60 ns in Gran Sasso and the 5 hour in the LSD. It is easy to juggle numbers to get any figure you want, but it is harder to explain two unrelated phenomena by the same equation. (Of course, it might be impossible as they are probably unrelated.) And, as Einstein showed us more than a century ago, it is even harder to fit several weird disparaged equations into a nice, simple theoretical model.

    We have 2 data point for a phenomenon most would rather ignore or forget. Who knows.

    But both the environment and energy of neutrino production are vastly different between the two.
    Never is a long time.
    Johannes Koelman
    A few words on LSD: this detector is of the same type as Baksan. No one has been able to explain why LSD would detect 5 earely events and Baksan none. Secondly, I can't stress enough that all SN1987a neutrino detection show very little (if any) dispersion. This invalidates all the crackpot models that emerged following the Gran Sasso anomaly.
    There's very little dispersion, except for the group that showed up 5 hours early to the party?
    This invalidates all the crackpot models that emerged following the Gran Sasso anomaly.
    Now if we could only make sure the neutrinos don't listen to any of the crackpots.

    While doing some reading about the detectors, it was mentioned that some were directional, could that be the difference between LSD and Baksan?
    Never is a long time.
    Oops, neutrinos reflecting off an object at 2.5 light-hours from SN1987A cannot be an explanation because the LSD neutrinos were before the others. Of course LSD might have captured the early ones, and all other detectors the reflected wave, but it does not make any sense whatsoever. LSD effects are known to be tricky, but a 5 hour trip backwards in time is preposterious!

    Anyway, thanks as always for a great article, Johannes. I remember that the late Dr. Feynman said: "Copernicus had his supernova, now I have mine!", however nothing interesting came out of it. But it is never too late.

    Bonny Bonobo alias Brat
    Very interesting article Johannes. I read quite a few of your links and came across this description at which describes how :- "The presence of the CνB affects the evolution of CMB anisotropies as well as the growth of matter perturbations in two ways: due to its contribution to the radiation density of the Universe (which determines for instance the time of matter-radiation equality), and due to the neutrinos' anisotropic stress which dampens the acoustic oscillations of the spectra. Additionally, free-streaming massive neutrinos suppress the growth of structure on small scales." Any chance you could explain what these 'free-streaming massive neutrinos' and their effects are in more laywoman terms please?
    My article about researchers identifying a potential blue green algae cause & L-Serine treatment for Lou Gehrig's ALS, MND, Parkinsons & Alzheimers is at
    Actually, Gran Sasso is not in North-Italy ...

    The path from Geneva to Gran Sasso is...

    I just want to say that I was born in 1987 only 3 weeks before this supernova neutron star. So I guess you can say that this star and I have a lot in common. I just want to know what is the current levels of neutrino on earth as of February 19 2012. I have been searching ever since my birthday when I also turned 25. I was told about all this when I was a kid by my grandpa and have been searching the sky and stars in the sky for another one to happen. So if someone can please let me know this number/count/level I would very much appreciate it. It would mean my wish came true and that there is something out there in space for me to see.

    I just want to say that I was born in 1987 only 3 weeks before this supernova neutron star. So I guess you can say that this star and I have a lot in common.
    You and 76 million other people. Happy birthday!

    There is no way to count neutrinos. Just the neutrinos from the Sun passing through Earth are around 65 billion per cm2 per second.
    yes I know that me and 76 million others were born and thank you for the belated happy birthday. I have read about 45 hundred articles that give you an equation to count or make an estimated guess on the levels. if you can't count the levels then why are so many scientists arguing recently?? I am not a scientist or have a scientists mind but I believe that if no one can count or guess on the levels then what is the point. I say this because it would and could help the whole world. doesn't neutrinos heat up the core and if another supernova comes from space or the sun wouldn't it be benefiting to know the numbers if in fact the core heats up too much to end the earth from inside itself?? Like my mother said,"things happen for a reason and some things are meant to be known to understand those things that do happen for a reason."

    doesn't neutrinos heat up the core

    Never is a long time.
    Challenged by acronyms .... A friend in the U.S. Armed Forces tells me about a career transition into the CIA (Central Intelligence Agency) with bootcamp-like classes by MTI (Military Training Instructors). Actually, the transition is into the CIA Culinary Institute of America. Then I read here about LSD … Liquid Scintillator Detector. Meanwhile, I'm toying with putting on my Steampunk goggles and getting a driving license from the DMV (Department of Mutant Vehicles) for my first Burning Man trip, kind of like Queens Day in Amsterdam, yet not on water. The theme for Burning Man 2012 is Fertility 2.0, not to confused with Science 2.0 Join The Revolution. I'll leave it to Google to parses it all for the Johaness Hit Parade with its AI (Artificial Intelligence). ~ blue-green algae cutting 'n pasting from 3 into good and dependable Mozilla Firefox in the interest of nuclear core meltdowns ~ mkb

    A double-collapse model of 1987a, from core collapse to neutron star and thence to black hole, was published in M. Aglietta et al "Comments on the Two Events Observed in Neutrino Detectors during the Supernova 1987a Outburst" Europhysics Letters v3,n12,p1321 (1987).

    A CERN preprint offers a tachyonic model in the arXiv. But note the date: perhaps the author was not being serious?

    Bad cable connection?

    "It appears that the faster-than-light neutrino results, announced last September by the OPERA collaboration in Italy, was due to a mistake after all. A bad connection between a GPS unit and a computer may be to blame.


    According to sources familiar with the experiment, the 60 nanoseconds discrepancy appears to come from a bad connection between a fiber optic cable that connects to the GPS receiver used to correct the timing of the neutrinos' flight and an electronic card in a computer. After tightening the connection and then measuring the time it takes data to travel the length of the fiber, researchers found that the data arrive 60 nanoseconds earlier than assumed. Since this time is subtracted from the overall time of flight, it appears to explain the early arrival of the neutrinos. New data, however, will be needed to confirm this hypothesis.

    This still leave open the question of where the neutrinos detected at LSD came from.
    Never is a long time.
    How one can ascertain those neutrinos are coming from sun and others from stars? After 25 years, of supernova happened, what is the state of the star there? Whether the core has turned into a neutron star?

    It will be right that Noise figure is expressed in dB. Smaller numbers correspond to lower noise and a greater ability to detect weak signals. we have zitterbewegung,brownian "t"(time) in schrodinger really T=TEMPERATURE?no "zag" for neutrinos?does this look much as wheeler's "one electron world" and feynman answer "there are no equal amount of positrons"(electrons cutting the other way the world line)?how about "sphere eversion"?entropic gravity>temperature?

    When you think you have seen it all:

    Demonstration of Communication using Neutrinos

    Beams of neutrinos have been proposed as a vehicle for communications under unusual circumstances, such as direct point-to-point global communication, communication with submarines, secure communications and interstellar communication. We report on the performance of a low-rate communications link established using the NuMI beam line and the MINERvA detector at Fermilab. The link achieved a decoded data rate of 0.1 bits/sec with a bit error rate of 1% over a distance of 1.035 km, including 240 m of earth.

    Great article brought the memories of SN 1987. 25 years ago, we were post graduate students. There were programme  to see the event through Telescope. I too written an article on SN1987 in Kannada (regional language) and that was published in the magazines. 
    25 long years have passed, but not fortunate enough to see another one. Some were I read, Betelgeuse - the red giant star of Orion is the best candidate. It might have exploded already. If so, we will have two suns in the day time. Hope we will soon have chance to observe !. 

    True, neutrinos will be flooded from Supernova. But number of neutrinos as observed by detector which kept at km depth in the underground probabaly dozen more! . How to ascertain this is due to that supernova? How to know the directionality? Also in SN1987 neutrinos came first then the light. Is it due to the fact that neutrinos interact very lightly with matter than photons? 
    Sol's system is undergoing a compression of the heliosphere, bringing it down from Pluto to near Mercury. It does this periodically. If we are blasted with neutrinos from hundreds of light years away, then how? by non-locality? And these events are all different. This one periodic event happening now is brief but implies our system was perhaps a dim sun with one or two planets close in if it can be compressed that far. It is not just solar wind either.

    Some questions about the LSD detector .
    It's the first time I hear about it and I am a neutrino loyalist for some time!!
    facts:- IMB, Baksan, Kamiokande measured neutrinos coincidently and LSD saw nothing at this time window.
    - LSD saw an excess 5 hrs earlier than the other three, and the three could not confirm it.
    This sounds like a systematic to me .
    Did they investigate their timing , cabling or noise issues? (Haven't found a paper so far about it)
    In OPERA they were lucky because they could measure their timing with LVD and exploiting the "Terramo Anomaly"

    Now about some other questions quoted above.
    Supernovae cannot be predicted when they will explode! We have some probabilistic of a few per century if I am right, if not please quote the nr!
    Therefore one cannot create a detector solely for detecting them (expect for some old and dedicated efforts - e.g LVD) . EVERYONE does something else in parallel.
    In elder days, they started with proton decay detectors and found SN neutrinos. That was sheer chance. When they kept going they measured atmospheric neutrino oscillations. But after the effect was established, this class of detectors had/has not much to do on its own.
    On the other hand, to me the most promising way to do is the IceCube way:
    They have the machinery, they search for point sources (which shall hopefully be seen - or after all, SOMETHING will be seen!!!) , but they have DeepCore - a low threshold extension to search for oscillations, and can spot supernovae by measuring a 
    coherent "flash" of Cherenkov radiation around their optical modules - some "neutrino noise"
    which will signal low energy nu-e interactions in the detector.

    One way or another, 
    SN neutrino physics .. Have they really got that much to tell us? Except for the fancy of the thing,
    what physics can we learn by them? If neutrinos are superluminal or not , by measuring speed vs energy (mayhaps IF there was a superluminal probability , it would be energy dependent?).
    But what else??

    Thanks for your time,