Name that Neutrino!

Is Name That Neutrino available in other languages?

Yes! With the help of IceCube and Zooniverse collaborators all around the world, we are have made translations in Dutch, French, German, Italian, and Spanish.

What is IceCube?

IceCube is a telescope and a particle detector encompassing a cubic kilometer of ice near the South Pole that studies neutrinos and other subatomic particles created in outer space.

Why is IceCube located at the South Pole?

The detection of very high energy neutrinos requires a huge, clear, and dark medium. The Antarctic ice sheet is not only pristine and stable but also one of the best neutrino detector materials Nature can provide. Thanks to the excellent ice properties, the dim light created by subatomic particles can reach sensors up to hundreds of meters away.

Why is my help needed?

IceCube is an instrument for both astrophysics discovery and high-precision particle physics. The light patterns produced by high-energy particles interacting in or near IceCube encode information that computers can process. However, the human eye is extremely good at recognizing patterns and, perhaps even more importantly, at identifying an unexpected pattern. That's why we would like to test signals that have been previously classified by a machine learning algorithm and compare with how the human eye would classify them. By asking volunteers to look at some of our data, we hope to further test our algorithms. Who knows, maybe they find strange light patterns that could help us learn more about IceCube and the Universe as a whole.

What is a signal or event?

Physicists refer to a detected interaction recorded by IceCube sensors as an event or signal. However, these interactions are happening all the time, sometimes so close together in time that it's hard to decide when to start recording and when to stop, or it may be that multiple particles interact at the same time. IceCubers, as IceCube collaborators are called, record an event every time eight neighboring sensors get light readings within a period of five microseconds. Every day, around 250 million events are recorded, about 2600 per second! Hidden among them are a few hundred events caused by neutrinos. And a tiny fraction of those are neutrinos coming directly from the extreme and distant Universe.

What are neutrinos?

Neutrinos are fundamental particles (they have no inner parts like atoms which have electrons, protons and neutrons for example), with very little mass and no electrical charge. In addition to the gravitational force, neutrinos interact weakly but they do not feel the strong nuclear force that holds particles together in the nucleus of an atom nor do they interact electromagnetically. For this reason, although neutrinos are the second most abundant known particle in the Universe, they can only be studied indirectly. In IceCube, we detect neutrinos through the blue light that is given off by high-energy electrically-charged particles produced when a neutrino hits the nucleus (and, at very high energies, an electron) of an atom and produces other particles, such as a muon or an electron. There are three known types of neutrinos: muon neutrinos, electron neutrinos, and tau neutrinos.

What are cosmic rays?

Cosmic rays are high-energy charged particles that originate in outer space and travel at nearly the speed of light. Most of them are atomic nuclei, mainly protons, but they also include electrons, positrons, and other subatomic particles. When these particles enter the atmosphere, they interact, producing a shower of secondary particles in the air, some of which reach the Earth’s surface, including muons and neutrinos that make it to IceCube. Very little is known about the origins or the properties of very high-energy cosmic rays, especially those of extragalactic origin. IceCube studies them both through very high-energy neutrinos produced in the same environments where cosmic rays are produced and through muons and neutrinos produced when cosmic rays interact with the atmosphere.

Why do neutrinos matter?

There are many reasons why they matter. For astrophysics, high-energy neutrinos coming from outside our solar system are ideal cosmic messengers. They travel mainly in a straight line that points to their origins, and their properties allow us to dig into the powerful physical processes that have created and still fuel the extremes of our Universe.

What are tracks in IceCube?

When a muon neutrino interacts in IceCube, it creates a muon as a secondary particle. The muon continues to travel across the detector, giving off a track of light as it moves. Tracks are long light patterns that travel in one direction along a straight line.

What are muons?

Muons are charged particles, very similar to electrons but about 200 times heavier. IceCube muons are relativistic, meaning that they travel at nearly the speed of light.

How can you tell if a muon was created by a neutrino and not a cosmic ray?

While neutrinos can travel through the entire Earth, muons cannot. So while muons can travel down into IceCube from the sky above Antarctica, only muons from neutrinos that have traveled through Earth can come up from the bottom of IceCube. The neutrino interactions in the Earth produce a muon that is able to make a signal in the IceCube array.

What are cascades?

The cascade is a light pattern that expands outward, creating more spherical signals in the IceCube detector. A cascade is a typical signature for an electron neutrino but can also be caused by other interactions. When an electron neutrino hits a nucleus, it transforms into an electron that interacts in the detector, producing a shower of particles. These also travel at relativistic speeds producing the same blue light that muons do. However, they quickly interact also, producing a reasonably spherical pattern of light.

What do the colored bubbles in the IceCube images represent?

The colored bubbles in IceCube signals represent the amount and the time sequence of light detected by IceCube's sensors. Larger bubbles indicate that more light was collected. The color corresponds to the progression of time, changing across the colors of the rainbow as time goes by, starting with red for early detections through green/blue for later detections.