IceCube Telescope Finds High-Energy Neutrinos, Opens Up New Era in Astronomy
After years of finding nothing, scientists at the IceCube neutrino telescope have detected 28 high-energy neutrinos that likely came from some of the most violent and powerful explosions in the universe. These are the precise results that IceCube was built for.
“We are seeing these cosmic neutrinos for the first time,” said physicist Francis Halzen of the University of Wisconsin-Madison, principal investigator of the IceCube collaboration. With these particles in hand, astronomers finally have a new window to the universe and may be able to figure out the details of mysterious processes that have so far eluded them. The findings appear today in a paper published in Science.
IceCube is a giant neutrino-finding telescope buried in the cold darkness 1.5 kilometers beneath the surface in Antarctica. With that much frozen weight above it, the ice at this location gets smushed, driving out any air bubbles and making it perfectly clear.
This allows the 5,160 light-sensitive detectors used in IceCube to see faint flashes across a large distance. Trillions of neutrinos pass like ghosts through the cubic kilometer of ice that IceCube is monitoring. Every once in a while, one of these tiny particles will crash right into the oxygen atom of a frozen water molecule, producing a faint blue spark. The flash of light tells scientists the direction and energy that a neutrino had when it flew into the detector.
Astronomers hypothesize that high-energy neutrinos are created in extremely energetic processes in the distant universe. Active galactic nuclei (AGN) and gamma-ray bursts are some of the brightest cosmic events that we see but researchers don’t really know how they work. Scientists speculate that giant black holes and collapsing massive stars are behind these mysteries but have yet to understand their mechanics.
Because they barely interact with anything, neutrinos get created in these events and then easily escape, shooting out in a direct line across the universe. These neutrinos have insane amounts of energy, more than a 1,000 times the energy that protons are smashed at CERN’s Large Hadron Collider. Astronomers hoped that IceCube would see these lively neutrinos, allowing them to trace back where in the sky they arrived from, and help them figure out what’s going on with the unexplained bright sources.
But after being completed in 2010, IceCube took a year’s worth of data and found zilch. Not even one neutrino. Well, that’s not entirely true.
“We actually see a neutrino every six minutes,” said Halzen.
These common neutrinos are created when charged nuclei called cosmic rays hit Earth’s atmosphere, generating a shower of subatomic particles, including neutrinos. After taking data for two years, though, IceCube had yet to see a high-energy neutrino coming in from outside our solar system. The non-detection concerned and frustrated scientists, who thought there might be something wrong in their models.
Then, help came from an unexpected direction. Some members of the IceCube team began looking through their data for ultra-high-energy neutrinos – 1,000 times more powerful than even those created in AGNs and gamma-ray bursts – created when a cosmic ray interacts with the cosmic microwave background radiation.
While combing through the ultra-high-energy data, the IceCube team also unexpectedly found two neutrinos in the right energy range to have come from an AGN or gamma-ray burst. The neutrinos were so rare, the collaboration named them “Bert” and “Ernie.” These two discoveries showed them how to analyze the data and spot the neutrinos the telescope was built to see. Now, knowing how to find the high-energy neutrinos, the team saw 26 more in their data from 2011 and 2012 that they had originally missed.
Most of the 28 high-energy neutrinos so far detected originate from parts of the night sky that don’t include the Milky Way, making it quite likely that they are arriving from a distant source. There are still too few neutrinos to make any specific conclusions about AGNs or gamma-ray bursts, but the IceCube team will continue gathering new data.
Halzen said the team is already using the new tactic to look through their 2013 data. They have found at least one more high-energy neutrino, the most powerful one yet seen, which they are calling “Big Bird.” Halzen said he expects to have enough neutrinos to say something about cosmic accelerator within about five years.
The findings are generating a good deal of excitement in the neutrino astrophysics community.
“I think this paper is one that will go into the textbooks,” said physicist John Learned of the University of Hawaii, who is not involved in IceCube. “It will be recognized as the beginning of high-energy neutrino astronomy.”
Every time scientists open a new window to the universe, they find unexpected things, added Learned. Already, the IceCube data has several new mysteries to ponder, including the fact that some of the neutrinos seem to cluster from a source near the center of our galaxy. If IceCube continues to see neutrinos from this source, it could point to an unexpected and interesting new process. Though scientists don’t know what that might be, “it’s certainly going to be something strange and new,” said Learned.
Description: High-Energy Neutrinos
“We are seeing these cosmic neutrinos for the first time,” said physicist Francis Halzen of the University of Wisconsin-Madison, principal investigator of the IceCube collaboration. With these particles in hand, astronomers finally have a new window to the universe and may be able to figure out the details of mysterious processes that have so far eluded them. The findings appear today in a paper published in Science.
IceCube is a giant neutrino-finding telescope buried in the cold darkness 1.5 kilometers beneath the surface in Antarctica. With that much frozen weight above it, the ice at this location gets smushed, driving out any air bubbles and making it perfectly clear.
This allows the 5,160 light-sensitive detectors used in IceCube to see faint flashes across a large distance. Trillions of neutrinos pass like ghosts through the cubic kilometer of ice that IceCube is monitoring. Every once in a while, one of these tiny particles will crash right into the oxygen atom of a frozen water molecule, producing a faint blue spark. The flash of light tells scientists the direction and energy that a neutrino had when it flew into the detector.
Because they barely interact with anything, neutrinos get created in these events and then easily escape, shooting out in a direct line across the universe. These neutrinos have insane amounts of energy, more than a 1,000 times the energy that protons are smashed at CERN’s Large Hadron Collider. Astronomers hoped that IceCube would see these lively neutrinos, allowing them to trace back where in the sky they arrived from, and help them figure out what’s going on with the unexplained bright sources.
But after being completed in 2010, IceCube took a year’s worth of data and found zilch. Not even one neutrino. Well, that’s not entirely true.
“We actually see a neutrino every six minutes,” said Halzen.
These common neutrinos are created when charged nuclei called cosmic rays hit Earth’s atmosphere, generating a shower of subatomic particles, including neutrinos. After taking data for two years, though, IceCube had yet to see a high-energy neutrino coming in from outside our solar system. The non-detection concerned and frustrated scientists, who thought there might be something wrong in their models.
Then, help came from an unexpected direction. Some members of the IceCube team began looking through their data for ultra-high-energy neutrinos – 1,000 times more powerful than even those created in AGNs and gamma-ray bursts – created when a cosmic ray interacts with the cosmic microwave background radiation.
While combing through the ultra-high-energy data, the IceCube team also unexpectedly found two neutrinos in the right energy range to have come from an AGN or gamma-ray burst. The neutrinos were so rare, the collaboration named them “Bert” and “Ernie.” These two discoveries showed them how to analyze the data and spot the neutrinos the telescope was built to see. Now, knowing how to find the high-energy neutrinos, the team saw 26 more in their data from 2011 and 2012 that they had originally missed.
Most of the 28 high-energy neutrinos so far detected originate from parts of the night sky that don’t include the Milky Way, making it quite likely that they are arriving from a distant source. There are still too few neutrinos to make any specific conclusions about AGNs or gamma-ray bursts, but the IceCube team will continue gathering new data.
Halzen said the team is already using the new tactic to look through their 2013 data. They have found at least one more high-energy neutrino, the most powerful one yet seen, which they are calling “Big Bird.” Halzen said he expects to have enough neutrinos to say something about cosmic accelerator within about five years.
The findings are generating a good deal of excitement in the neutrino astrophysics community.
“I think this paper is one that will go into the textbooks,” said physicist John Learned of the University of Hawaii, who is not involved in IceCube. “It will be recognized as the beginning of high-energy neutrino astronomy.”
Every time scientists open a new window to the universe, they find unexpected things, added Learned. Already, the IceCube data has several new mysteries to ponder, including the fact that some of the neutrinos seem to cluster from a source near the center of our galaxy. If IceCube continues to see neutrinos from this source, it could point to an unexpected and interesting new process. Though scientists don’t know what that might be, “it’s certainly going to be something strange and new,” said Learned.
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