AMANDA Maps Cosmic Neutrinos

Uosdwis writes "Remember those 'little neutral ones', neutrinos? You know those little guys have no charge, are invisible and just about no mass. Well a University of Wisconsin-Madison professor has created an array, burried in the antarctic, to detect them with help from the National Science Foundation and produced a map of nuetrinos in the cosmos. A different method than the tau neutrinos found a few years ago, and show the 'natural' neutrinos are at a higher energy level."

Comments

link to the map?

[alonsoac]

Any one has a url to the map itself?

Re:link to the map?

[DustMagnet]

Right here.

Link to AMANDA site

[Anonymous Coward]

Posted AC to avoid the appearance of Karma Whoring.

AMANDA Maps Cosmic Neutrinos

It's probably just as well the link wasn't included in the original story, 'cause I bet it won't take many downloads of those multi-meg .jpg files to bring the server to its knees!

Re:Link to AMANDA site

[corkhead0]

Holy crap, with the huge file and netscape 7.1's auto zooming thinger, it felt like I was back on dailup for a second (shudder).

Compression ratio of more then %1 please?

Wow

[pmsyyz]

Wow, I didn't know The Advanced Maryland Automatic Network Disk Archiver had that feature.

duh?

[greywire]

" The glass modules work like light bulbs in reverse"

Is this a stupid analogy or what? This can be said about any type of light detector. This is like saying a digital camera works like a light bulb in reverse... duh? So these "modules" are just simply really sensitive digital cameras networked together.

When I first read about these things I thought it had something to do with solid glass spheres that for some reason, in combination with the ice, had optical properties that allowed them to capture neutrinos. No, they're just cameras. Why make it sound more complex than it really is?

Re:duh?

[Christopher Thomas]

Is this a stupid analogy or what? This can be said about any type of light detector. This is like saying a digital camera works like a light bulb in reverse... duh? So these "modules" are just simply really sensitive digital cameras networked together.

Not quite. These are photomultiplier tubes, designed to detect single photons. A photon strikes a photosensitive material, generating an electron. This electron is accelerated down a high-voltage tube, knocking additional electrons free from electrodes, creating an electron cascade that can be detected.

The electron cascade may or may not be detected using camera-like photosensors (using a phosphor screen to turn the electron cascade back into light) (nightvision goggles do something like this, photon-counting tubes may measure the charge transfer directly).

When I first read about these things I thought it had something to do with solid glass spheres that for some reason, in combination with the ice, had optical properties that allowed them to capture neutrinos.

Ice is used because it's reasonably transparent. That's about it. Neutrino detection in this detector seems to be purely based on scattering of neutrinos against other particles with enough energy to produce Cherenkov light as the other particles fly off. How they plan to focus exclusively on muons is beyond me. With electron neutrinos you'd mainly get electron scattering as opposed to direct synthesis of muons. While mu neutrinos could produce muons via Weak-force interactions, they'll have scattering interations as well, and you have plenty of electron neutrinos present too.

A good introduction to neutrino detection is at http://www.sno.phy.queensu.ca/sno/sno2.html (Sudbury Neutrino Observatory page).

No, they're just cameras. Why make it sound more complex than it really is?

Cameras produce images. Photomultiplier tubes don't (they just indicate that a photon hit the tube). Determination of the path of the neutrino is done by looking at the timing of photon events in many detectors in the array, and looking at which detectors registered events at all.

Re:duh?

[hubie]

The glass spheres are just pressure housings for the photomultiplier tubes. You want glass because you want light to pass through, and you want a sphere because it is easy to make as well as being the best shape to stand up against pressure (they drill a kilometer into the ice, lower down a string of these detectors, then fill the hole back with water to refreeze).

Ice is used in this case because you want these detectors deep under the Earth's surface to shield from atmospheric muons and other background particles. This experiment exploits the fact that Antarctic ice is very clear and deep. Similar experiments have been done by dropping PMTs deep into the ocean (as well as the Sudbury and SuperK experiments that use water tanks in deep underground facilities).

You can differentiate between electrons and muons pretty easily in a Cherenkov detector because electrons produce much more light and in a much larger cone from both the initial electron as well as the electrons that get produced in the ensuing electromagnetic cascade. Muons won't produce the EM cascades. The cosine of the Cherenkov light cone angle goes as the inverse of the particle velocity, and the number of photons produced goes as 1 minus the inverse of the velocity.

Re:duh?

[tektrix]

Photomultipliers tubes (which are the devices used in this observatory) are similar to a light bulb working in reverse. In a light bulb, a flood of electrons (either in an arc/plasma, filament, or semiconductor) are converted to light. In a PMT, the reverse happens . . . photons initiate a flood of electrons. In a digital camera, light knocks a few electrons about, creating a minute charge that is clocked out of the chip . . . not at all like a PMT. Capturing a neutrino, eh? Uh... hardly. This system records the "shockwave" (Cherenkov radiation) created by something moving faster than light through a medium (yeah, yeah... but that's in a vacuum). Duh!

SETI Anyone?

[TechnoGrl]

I can't help but wonder if a high tech civilization using fission, fusion, antimatter and who knows what.... would generate high levels of nutrino flux and if results from detectors such as these could be used as a device to detect such?

Re:SETI Anyone?

[Eccles]

I can't help but wonder if a high tech civilization using fission, fusion, antimatter and who knows what.... would generate high levels of nutrino flux and if results from detectors such as these could be used as a device to detect such?

I'd think you would need an incredibly sensitive detector in terms of determining the angle of origin of the neutrinos. Remember that most such civilizations will have an enormous fusion reactor -- aka a star -- right nearby, generating more such particles than the civilization would.

Re:SETI Anyone?

[Christopher Thomas]

I can't help but wonder if a high tech civilization using fission, fusion, antimatter and who knows what.... would generate high levels of nutrino flux and if results from detectors such as these could be used as a device to detect such?

While a civilization using any of several varieties of nuclear power could produce substantial neutrino emissions, these would be swamped by the neutrinos emitted by their parent star.

Also, the fusion reactions proposed for power production do not produce substantial numbers of neutrinos. Neutrino production occurs in Weak-force interactions, which tend to have cross-sections lower than the Strong-force interactions that dominate the various fusion schemes involving D, T, and/or He3. The sun produces neutrinos because to get hydrogen (p) turned into helium (2p + 2n) you need Weak-force interactions to produce the neutrons. Thus, plain hydrogen fusion produces neutrinos because there are no fusion paths that _don't_ (this is also one of the reasons why fusing plain old hydrogen is very difficult).

The idea behind SETI is to search for alien transmissions in bands where there is relatively little ambient noise. Neutrino emission isn't such a case.

Interesting idea, though.

Yes and no.

[rjh]

Yes and no. Yes, neutrinos are created in many kinds of nuclear reactions, and yes, they do travel at lightspeed with some awe-inspiring ability to travel clear through anything, and yes, they could be used for SETI; but no, nobody's going to be using them for SETI.

The reason for this is any civilization advanced enough to have fission--much less fusion, MAM, quark-gluon conversion or other exotic energies--is first going to progress through a much lower-tech level, during which point their civilization is going to glow like a supernova in certain bands of the electromagnetic spectrum. (Earth, for instance, far outshines the Sun in several wavelengths.)

Rather than peek at the cosmos with a neutrino telescope to see the (relatively small) signatures of an individual fusion reactor here or there, it makes more sense to look at the cosmos with radio-astronomy tools to look for planets that are brighter than stars. Find one like that, and dollars to donuts says it's got intelligent life.

To give you an idea of just how quiet the cosmos is... if you were to stand on Pluto and turn on a cell phone, you'd create a radio signal so loud it would drown out literally everything in the night sky (at least on its band). It's quiet out there.

Re:Yes and no.

[hubie]

I don't think I can agree with you, unless my rough calculation is messed up.

The Cosmic Background Radiation at about 900MHz is about 10^(-21) W/(m^2 sr Hz). A 3 W cell phone radiating into a sphere puts out per square meter about 2.5x10^(-10) W/(sr Hz). This means that the strengths of the two signals are equal at about 500,000 meters, or only 500 km. Pluto's diameter is about 2,000 km, so you'd be lost in the noise without even leaving Pluto.

Link to a different map

[A55M0NKEY]

http://newscientist.com/news/news.jsp?id=ns9999395 2

Dark matter map seems to show that neutrinos are not the 'dark matter' people talk about.

DarkWing Duck! Let's get dangerous.

Re:Link to a different map

[Luigi30]

Really? I thought dark matter was alien poop.

AMANDA

[Red Rocket]

"Amanda Huggankiss! I need Amanda Huggankiss!"
-Moe

Not a signal map

[EigenHombre]

Hi, I work for this project (or rather its successor, IceCube) and I have to clarify something. I believe the sky map shown is a map of neutrino BACKGROUND events, not a map of neutrino sources. Background events occur when energetic cosmic rays strike the earth and produce neutrinos which travel through the earth and trigger the detector. Any extraterrestrial neutrino sources would show up as "hot spots" in the sky map under discussion (with the exception of diffuse sources). At this point, AMANDA is NOT claiming the detection of any extraterrestrial source, AFAIK. Most predicted sources are thought to require a larger detector, which is currently under construction.