HESS Gamma-Ray Telescope Inaugurated This Week

Grandroyill writes "Most ground-based telescopes with lenses and mirrors are hindered by the Earth's nurturing, protective atmosphere that blurs images and scatters and absorbs light. But this telescope...actually requires the atmosphere to operate. As the gamma rays impact the upper atmosphere they produce air showers of high-energy particles. Adorned with 382 separate mirrors each 60 centimeters in diameter and equipped with a fast camera, the telescope records in detail the brief flashes of optical light, called Cherenkov light, created by the air shower particles. Great pic too!" Beautiful telescope. Kudos to the engineers.

Comments

A distributed array?

[littlerubberfeet]

Are gamma rays specific to an atmospheric location? or can several of these be used for overall measuring of gamma radiation in the atmosphere?

Also, it should be possible to find unstable radioactive isotopes that react to gamma rays. One could measure the change in these isotopes when gamma rays hit them, thus measuring the gamma rays. Has anyone played with this? I suppose it would only be possible in space, before the gamma radiation is filtered by the atmosphere

Re:A distributed array?

[esonik]

These Telescopes measure gamma rays with energies above 40 GeV, far above enegies of nuclear decay (MeV range, a factor of 1000 less). The HESS project page contains more information, about the (cosmic) origin of these gamma rays.

One could measure the change in these isotopes when gamma rays hit them, thus measuring the gamma rays. Has anyone played with this?

You are talking about the nuclear "photoelectric" effect. It is in principle possible, but very inefficient (nuclei do not capture gamma rays very well). Actually this was initially researched by W. Gentner in the 1930ies in Heidelberg, where they now build the HESS telescope (among others).

Re:A distributed array?

[Anonymous Coward]

How important is this to research? I would think that there are very few practical applications.

Re:A distributed array?

[esonik]

Do you mean the HESS telescope or the nuclear photoelectric effect ?

Both are basic science - there is no immediate practical application (and usually you don't start basic science with practical applications in mind). That is also the reason why these projects are run by the Max-Planck Society, which is the German organization for cost-intensive basic research.

For the HESS, the goal is to understand the creation and origin of the very high energetic particles that are observed in cosmic radiation. You can get more detailed answers at the site linked in my previous post if you proceed to the section "Exploring the nonthermal universe" on the left sidebar.
For the nuclear photoelectric effect, I do not know much about that. I assume the goal was initially to verify theory and get some values for the "effectivity" of the process, which would e.g. be important for calculations concerning nuclear reactors, nuclear waste, or nuclear reactions in stars (like our sun). Also, the photoelectric effect is a very simple and basic phenomenon and quite important and useful in its "conventional" (=non nuclear) form (think solar cell, photodiode etc.) and therefore it is important to know more about it in its nuclear analogy, too.

big one

[Anonymous Coward]

Thats alot of mirrors to put together.

Small parts, not for children under 6. Batterys not included.

Masts?

[SagSaw]

There appear to be four masts surrounding the telescope (two visible, looks like there are guy wires for two mre). Anyone know what these are for? (Maybe lightning protection?)

Just add a link to APOD on the main page

[Anonymous Coward]

Seriously, I'm getting tired of seeing every day's astronomy picture of the day submitted as a slashdot story. Just make it a slashbox on the front page and reject all the submissions.

lightning forecast

[Perdo]

Must be lightning protection - check the weather there

Also get a load of the parts left over in a pile in the foreground of the picture... If you had that many parts left over after building a computer, not only would it not run, but you'd probably smoke something.

HESS technology not new

[Anonymous Coward]

The HESS gamma-ray technology actually isn't a new thing. HESS (High Energy Stereoscopic System) has been in use at several German sites, mostly universities, since the early 1990s. It's just now making its way into the US.

HESS is a next-generation system of telescopes for the investigation of cosmic gamma rays in the 100 GeV energy range. The name HESS should also remind you of Victor Hess, who received the Nobel Prize in Physics in 1936 for his discovery of cosmic radiation. The acronym also emphasizes two main features of the proposed installation, namely the simultaneous observation of air showers with several (3 to 4) telescopes, under different viewing angles, and the combination of multiple (up to 16) telescopes to a large system to increase the effective detection area for gamma rays. With telescopes of over 100 m2 mirror area, the proposed system provides a detection threshold of about 40 GeV, full spectroscopic capability above 100 GeV, an angular resolution for individual showers of 0.1 degr., and an energy resolution of about 20%. It will allow to explore gamma-ray sources with intensities at a level of a few thousandth parts of the flux of the Crab nebula. HESS is located in Namibia, near the Gamsberg, an area well known for its excellent optical quality.

As some ./'ers may know, the first four HESS telescopes (Phase I of the HESS project) are under construction and are expected to go into operation between 2002 and 2004.