Breathtaking aurora and stars over IceCube
As far as inhospitable environments go, you can’t get much harsher than an elevated plain at the South Pole. For half the year, the sun doesn’t even appear there, gale-force gusts may whip across the snow, and temperatures can swoop down to less than -100° F (-73° C). It’s no wonder very few humans choose to live in this place. However, there is one group of people for whom the South Polar conditions are perfect: astronomical researchers. This fact was confirmed by an incredible discovery recently made there.
IceCube explores the universe not by gazing at the stars but by peering under the ice.
While the long periods of darkness and dry air are perfect for sky gazing, there’s one observatory here that has its attention focused downwards. The IceCube Neutrino Observatory boasts a huge multitude of sensors buried under at least 0.24 cubic miles of Antarctic ice. Its target is high-energy neutrinos – a type of nearly massless, neutrally charged subatomic particles that form in the depths of space. In 2013 IceCube discovered an amazing 28 of these cosmic neutrinos, which may have been born of a cataclysmic event such as a supernova or gamma-ray burst.
The Southern Lights illuminate the sky over the Amundsen-Scott South Pole Station.
Neutrinos are produced when radioactive matter decays, particularly during high-energy events such as nuclear reactions and supernova explosions as well as in particle accelerators like The Large Hadron Collider at CERN. Cosmic neutrinos could provide us with data about cataclysmic episodes that happened millions if not billions of years ago, far away from our solar system – which of course makes them a fascinating source of information to researchers.
IceCube makes an impressive sight in this remote location.
IceCube scientist Francis Halzen talked to Astronomy magazine about the recent cosmic neutrino findings. “This is the first indication of very high-energy neutrinos coming from outside our solar system, with energies more than 1 million times those observed in 1987 in connection with a supernova seen in the Large Magellanic Cloud,” he said. Halzen also described his joy in making the amazing discovery, saying that it marked “the dawn of a new age of astronomy.”
Icebreakers such as the Oden were employed to transport hefty equipment for IceCube.
IceCube has been searching for neutrinos for around three years, since its construction was finished in 2010. It incorporated and finally replaced the earlier Antarctic Muon And Neutrino Detector Array (AMANDA), which was shut down completely in 2009. However, it wasn’t until 2013 that researchers at IceCube found their first evidence of high-energy neutrinos from beyond our solar system.
An aurora lights up a winter night at IceCube.
The discovery of these deep-space neutrinos won IceCube Physics World magazine’s “Breakthrough of the Year” award in 2013. “The ability to detect cosmic neutrinos is a remarkable achievement that gives astronomers a completely new way of studying the cosmos,” said Physics World editor Hamish Johnston.
Two people, known as winterovers, stay on at IceCube during the harsh winter.
IceCube consists of thousands of ice-submerged, neutron-detecting sensors. The ice of Antarctica is particularly suited for this because it is exceptionally transparent. During construction, a high-pressure hose of hot water was used to drill 86 holes deep in the ice. Next, spheres called Digital Optical Modules (DOMs) were planted in the ice in strings of 60 per hole.
IceCube seen in the bright Antarctic light
The depth of the sensors ranges from 4,757 to 8,038 feet (1,450 to 2,450 meters). Here, the weight of the ice pushes out any potential air bubbles, which explains the clarity of the ice previously mentioned. As neutrinos travel through the ice, which they do in their trillions, some will collide with oxygen molecules and release Cherenkov light – small flashes that can be detected by the DOMs.
The incredible sight of the aurora australis (southern lights) swirling above the lab
Common neutrinos are observed at IceCube about every half dozen minutes, according to Halzen. These are the result of cosmic rays that produce a flurry of particles – such as neutrinos – on contact with the Earth’s atmosphere. However, it was the less common high-energy neutrinos, from beyond the solar system, which scientists have really been hoping to find. In the end, it turned out that the problem wasn’t that IceCube wasn’t detecting these cosmic particles, but that the human researchers needed a different way of looking at the data.
The lights of IceCube make it a beacon in an otherwise empty landscape.
It wasn’t until researchers began sifting through two years’ worth of data from IceCube – focusing on ultra-high energy bursts (greater than 50 teraelectronvolts (TeV) – that they found their first cosmic neutrinos. These particles have 1,000 times the energy of the regular neutrinos.
A warmly dressed winterover stands outside a hut at night.
The powerful neutrinos are believed to be from a far away source in the universe, some of them mysteriously originating from patches of sky beyond the Milky Way. Their discovery has understandably generated much excitement in the world of astrophysics. A long way from IceCube, University of Hawaii physicist John Learned believes the findings “will be recognized as the beginning of high-energy neutrino astronomy.”
The Amundsen-Scott South Pole Station provides accommodation for those working at IceCube.
The IceCube Observatory is itself something of a marvel. It took seven years to build the lab, which is a project of the University of Wisconsin-Madison. Forty-one research and educational institutions from around the world have collaborated and contributed funding to the observatory. Together, this group is known as the IceCube Collaboration. Members of this collaboration include scientists, software experts, engineers and grad students; almost 250 people in all.
One of the perks of wintering at IceCube is a front-row seat for the spectacular auroras.
As you might guess, there were plenty of trials involved with the construction of this major research facility in the Antarctic. According to Halzen, these ranged from “from deciphering the optical properties of ice that we have never seen to drilling a hole to 2.5 kilometers in two days, and then repeating 86 times.” Then of course there was the weather to factor in. Construction on IceCube could only happen through the warmer months between November and February.
IceCube seen from the above
The people who work at IceCube stay at the South Pole Station, which accommodates about 200. They need to get used to living in the thin air of a high-altitude station – almost 10,000 feet above sea level – not to mention the Antarctic conditions. Station winterovers (winter maintenance crews) spend their days in artificial light, as the sun does not rise at all during this period. Fortunately, the experience of spending time in such a pristine and beautiful environment, coupled with the astonishing scientific work taking place at IceCube, would likely more than make up for any challenges.
The moon shines down on the IceCube lab.
The new data coming from IceCube is incredibly exciting for those interested in astronomical research. As Halzen says in Astronomy magazine, “Now that we have the full detector, we have the sensitivity to see these events. After seeing hundreds of thousands of atmospheric neutrinos, we have finally found something different. We’ve been waiting for this for so long.”