IceCube Telescope Takes Shape Below Antarctic Ice 165
PabloSandoval48 writes "The world's largest telescope, currently under construction more than a mile beneath the Antarctic ice, is on schedule to be completed next year, according to a researcher at the University of Wisconsin, the lead institution for a scientific project called IceCube."
Not a telescope (Score:5, Informative)
Re:IceCube? (Score:4, Informative)
Re:But... (Score:5, Informative)
IceCube is a neutrino telescope which looks through the Earth to the Northern Hemisphere. The Earth basically acts as a filter removing potential background signals.
Re:Not a telescope (Score:2, Informative)
Re:Telescope? (Score:3, Informative)
Why? It captures information from a flux of particles (not photons, but neutrinos in this case) emitted by astrophysical objects. It allows us to study properties of those objects (and of the detected particles as well). It doesn't have a resolution high enough to give us an "image" of most of those objects, but Hubble can't image most single stars too. IceCube won't give you a pretty picture for APOD, but it will do everything else we can do with an optical telescope, or a charged particle telescope such as Auger [auger.org].
Re:Interesting... (Score:5, Informative)
Re:World's largest, eh? (Score:3, Informative)
One cubic kilometer is not 1000 cubic meters.
Re:World's largest, eh? (Score:4, Informative)
> This thing has a volume of about 1,000 cubic m.
1 cubic km. That's 10E9 cubic m.
Re:World's largest, eh? (Score:2, Informative)
Muons, not neutrinos (Score:5, Informative)
There's a deficit of muons, not neutrinos, from the moon's direction. Neutrinos pass through the moon easily.
Re:Interesting... (Score:5, Informative)
Would there, however, be any benefit to having such a project set up under lunar regolith/base rock if we could ever get back to the moon?
Yes.
The reason why: there are virtually no high-energy muons in lunar cosmic rays, and high-energy muons, one way or another, are the major cosmic-ray background in these experiments.
The reason why there are virtually no high-energy muons in lunar cosmic rays is due to their primary mechanism of production: on Earth, cosmic-ray protons smack into atoms at the top of the atmosphere, producing high energy pions, which decay into muons etc... and because of the low density of the atmosphere, the decay time is much less than the stopping time, so the muons have most of the orignal energy of the primary cosmic ray available to them.
On the Moon, which notably lacks an atmosphere, the primay cosmic rays smack into the lunar regolith and therefore the pions are created in a very dense medium, and lose most or all of their energy before decaying. The muons thus created are relatively low energy and stop within a few meters--as opposed to terrestrial cosmic ray muons which are still seen in experiments like the Sudbury Neutrino Observatory, 2 kilometres underground.
As such, a relatively small, relatively shallow detector on the Moon could produce comparable performance to the best terrestrial detectors, at only a few orders of magnitude higher cost.
It may be worth mentioning that no one working in the field ever calls a neutrino detector a "telescope", as in English that word when used without qualification virtually always means "optical telescope", so the usage in this article is misleading and confusing, to the point where if were done deliberately I would consider the person doing it to be either stupid or dishonest. I guess maybe the person who wrote the article or provided the information for it has English as a second language.
Re:It is a big problem (Score:4, Informative)
Re:Not a telescope (Score:3, Informative)
Re:But... (Score:5, Informative)
But that's what it sees - the sensors point at the Earth and the filter software discards muon events that track from the sky, keeping events that come from underneath since muons coming from the Northern Hemisphere decay long before they can reach the detector. Neutrinos survive passing through thousands of miles of rock, so if it comes from the middle of the Earth, it's a neutrino. If it comes from the sky, it could be a neutrino, but chances are, it's a muon.
Re:World's largest, eh? (Score:1, Informative)
> This thing has a volume of about 1,000 cubic m.
1 cubic km. That's 10E9 cubic m.
No, 1E9 cubic meters.
Re:Interesting... (Score:3, Informative)
I agree that the background reduction due to lack of atmosphere is very convenient, but as zero.kalvin points out, you still need a 'refracting medium', that is, a really large volume of transparent material such as water or ice (in which you can catch the Cherenkov light whenever a neutrino is kind enough to interact and produce fast charged particles). The large volume is not needed to suppress background, but to beat the very small cross section; in order to detect neutrinos you need them to interact with your detector, and the only way to achieve that is to make it as big as possible.
There is ice on the Moon, but to harvest that and turn into a detector poses some interesting challenges. To use it in frozen form is hard, because you need it with a clarity and purity similar to the exceptionally clear deep Antarctic ice that IceCube uses and which is even clearer and purer than laboratory ice. To use it in liquid form requires keeping it heated, which is probably easier (you need a solar panel farm to power the heating system, but for the ice option you would also need those panels, to power the elaborate purification system + clear ice machinery). Either way: probably science fiction.
Re:Muons, not neutrinos (Score:4, Informative)
Not all the neutrinos, just nearly all. The moon is large enough to catch a statistically discernible (to IceCube) amount of neutrinos, casting a "neutrino shadow" on the Earth.
Re:Interesting... (Score:4, Informative)
Re:Not a telescope (Score:3, Informative)
It's ability to trace the sky using a carrier that was never explored in this way (except to "see" what happens in the sun, and during a nearby supernova).
Using optical telescopes, we can get an image of how the universe looks in visible photons. In an x-ray telescope, we get an image of the universe in x-ray photons. In a cosmic ray telescope, we get an image in charged particles. IceCube (plus its northern sister, KM3Net) should be able to get an image of the universe in neutrinos with energies over 1 TeV.
Re:World's largest, eh? (Score:3, Informative)
The Hubble doesn't count because it's nowhere near the largest. It doesn't even make the top 50 list, more like around 55'ish. The Hubble gets great images because it is in space, and doesn't have to deal with atmosphere and light pollution. It can also catch wavelengths that are largely absorbed by the atmosphere, like infra-red and UV. That makes it extremely useful, however almost all of the ultra-long range research (~13 billion light years) is done with earth based telescopes and fancy corrective software to account for the affect of the atmosphere.
The two largest telescopes are each about four times larger than the Hubble.
Wait, why are we speculating? (Score:4, Informative)
The IceCube website and U Wisc. [wisc.edu] says it's a telescope. So, case closed as far as I'm concerned.
Re:It is a big problem (Score:2, Informative)