Wednesday, April 30, 2014

Podcast: The Askaryan Radio Array

There's more to the South Pole than just some ice and a pole. A lot more. In fact the bottom of the world is a veritable hot bed of international scientific experiments. Like the Askaryan Radio Array, subject of this week's podcast.

The pole at the South Pole in front of the Amundsen-Scott South Pole Station.
Image: NSF

Antartica's arid conditions offers researchers night skies clearer than almost anywhere on planet Earth, and its extreme isolation means that there's little radio interference from human sources. That plus the vast fields of ice that cover the continent make the South Pole the perfect place for experiments like the Askarayn Radio Array to look for ultra-high-energy neutrinos.

ARA's horizontal and vertical radio antennas are buried deep under the ice's surface.
Image: ARA Collaboration

When it's completed, ARA will have 37 antenna stations buried deep in the ice, listening for the faint radio signals of neutrinos striking the nearby atoms of frozen frozen water. It's going to be big too, covering nearly 100 square kilometers.

The collaboration is right now budgeted to build 10 of their planned 37 detectors over the next two years.
Image: ARA Collaboration
This schematic shows where the different radio antenna stations are going to be buried in relation the South Pole and nearby Amundsen-Scott South Pole Station (the red circle and brown rectangle on the far right). For perspective, compare ARA to IceCube, another similar neutrino detector also buried in the ice. On the map, IceCube is the small gray hexagon to the left of the pole.
The IceCube Neutrino Observatory next to ARA offers a sense of scale.
Image: IceCube Collaboration
It's easy to miss, but there to the right of the array is how big the Eiffel Tower would be if it were buried next to IceCube. Extrapolate that out, and you get a sense of scale for ARA. IceCube and ARA do a lot of complementary science. In April, the IceCube collaboration announced they detected the highest energy neutrino ever recorded. Dubbed "Big Bird," it clocked in at over 1 petaelectron volt. Once finished, ARA should be able to detect neutrinos 100 times as energetic.
Even supernovas like SNR 0519 shouldn't be able to produce the highest cosmic rays seen on Earth.
Image: NASA
Scientists hope that ARA will be one more step towards solving an interstellar mystery, the source of the highest energy cosmic rays. Ultra-high energy cosmic ray particles create their own neutrinos through something called the GZK effect. Researchers hope the neutrinos produced this way will point back to their original sources because right now, astronomers have no idea where the highest energy cosmic rays are coming from or even what could be powerful enough to create them. Though ARA won't be sensitive enough to be used as a neutrino observatory, it could be the first to see these GZK neutrinos helping to lay the foundation for future observatories.


  1. Hello, this is a great article! I just wanted to point out that the completed ARA will have 37 antenna stations, instead of 37 antennae in total. Each stations is projected to have 16 deep antennae.

    1. Thanks for pointing that out. Fixed it!