Pierre Auger Observatory

I’m in Patagonia now, but before getting to that how about a brief tour of the Pierre Auger Observatory where I was this past week? We’ll start off driving six hours from Mendoza on the western side of Argentina through the magnificent desolation with the Andes in the distance-


(We’re so in the middle of nowhere that one of those peaks is where the Miracle of the Andes plane crash occurred in the 1970s.  Yup, I heard many a cannibalism joke this past week.)

Anyway, several dozen kilometers outside the small town of Malargue if you pay very close attention you start noticing these, spaced out every kilometer or so-

You usually don’t see much more than this to be honest, just maybe another tank or two further in the distance if you’re lucky as they’re spread about a kilometer apart from each other.  It’s just when you keep driving further and further and keep coming across these tanks that you start to realize the size of the array- larger than the state of Rhode Island- which makes me wonder what people think who come across them unexpectedly.  What are they for?  Eventually if you keep going down the road (there’s only one road worth mentioning in this part of the world) you come across the answer, the Pierre Auger Observatory headquartered in Malargue!


The observatory building is pictured here, and I gotta say I’m in love with whoever thought of the trellis as this time of year it’s covered in blooming roses and acacia.  There are worse fates in life than having to endure two springtimes in a year, unless you have allergies I guess.

Some art in the observatory building itself that I liked to the point of contemplating if there was an easy way to steal it, and serves the dual purpose of giving me the excuse to explain just what these water tanks spread out over remote Argentina and run by 250 scientists are for.  In short we are looking for supremely energetic cosmic ray particles that only happen once a square kilometer a century (a search I explained in more detail here), but it’s very unlikely you’re ever going to see the particle itself for obvious reasons pertaining to how small they are.  When a particle streaks through the atmosphere, however, it interacts with particles already there and creates a particle shower which spreads out over several square kilometers.  These interactions are very well understood in physics (similar to how chemists know exactly what compounds they’ll get in a reaction) so when you look at the shower on the ground you can work backwards to figure out things like what direction the original particle came from and how energetic it was.

Our 3,000 square kilometer array detects about one of these every other month, and you can figure out the direction to within a few degrees (to compare the moon is half a degree in the sky, so this isn’t exactly a precise science yet).  The statistics are still out as to their origin and composition, but we didn’t even know particles with such energies could exist until a few years ago so it’s tremendously exciting to see what we find out!

Last but not least, a water tank next to the observatory complete with a bicycle for scale- not too big, but not terribly small either.  The whole thing is filled with water and when particles streak through the tank it records the vital details as well as the other ones around it so we can reconstruct the details (it goes without saying that all these tanks are equipped with a GPS unit, and playing around with those is what I do!).  Well over a thousand of these are out in the field right now and this has led to all sorts of unexpected problems- for example birds like to nest under the solar panel but this material is just enough to ignite in a lightning strike, so lots of the collaboration was spent discussing “black tanks” which burned down in this manner.  Stupid birds.

It really is exciting to see science as it unfolds, particularly if you’re lucky enough to get involved in the unfolding.  And with that, let me leave you with a picture snapped on the same road but in the opposite direction as I was leaving on the bus- the thunderstorm approaching was so rare all the locals started snapping with their cameras when it began to rain…

2 responses to “Pierre Auger Observatory

  1. Pingback: Photo: What Science Looks Like | Where is Yvette?

  2. Pingback: So my article made the cover of Astronomy Magazine… | Where is Yvette?

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