Catch Neutrinos: How Scientists Look for Answers in Particles Arriving on Earth from All Over the Universe

Neutrino Observatories

Cosmic rays - streams of elementary particles moving with high energies in

outer space, first recorded in 1912. Such particles are constantly bombarding the Earth, but to trace their source is quite difficult.

Since cosmic rays are not only composed ofneutral particles (or neutrinos), but also from charged ones, they interact with the magnetic field of our planet. This interaction changes their trajectory and makes it difficult to determine the source of radiation.

At the same time neutral particles freely passthrough magnetic fields, following the originally specified trajectory. Every second about 100 billion neutrinos pass through one square inch of your body. Most of them are formed by the fusion of protons on the Sun and are not energetic enough to be identified, but some reach our planet from outside the Milky Way.

On Earth, neutrinos are very difficult to fix -these fundamental particles almost do not interact with matter, with the exception of rare cases of neutrino colliding with the nucleus of an atom and the nuclear reaction following it.

The consequences of such nuclear reactions are almost invisible: When neutrinos collide with the nucleus of an atom, Cherenkov radiation arises - a weak blue glow, which is visible only in very pure water or in ice. The radiation stores information about the trajectory of the neutrino and allows you to calculate the energy of the particle. This allows physicists to study rare particles despite the fact that they are reluctant to interact.


Most of the ice contains air bubbles,which form voids and distort the neutrino trajectory data. But at depths of more than 2 km at the South Pole, the ice is a homogeneous structure without bubbles - the pressure in it is so great that the ice shrinks and forces out the air until it becomes “clean”.

IceCube Mission

This feature of the deep Antarctic icePhysicists from the IceCube mission took advantage - the observatory built by them is located at a depth of 2.5 km under the Amundsen-Scott research station and represents a neutrino detector with an area of ​​about 1 cubic meter. km

The station is equipped with 56 "strings" and 5.2 thousand. optical sensors. Particles pass through the strings, and optical sensors attempt to detect a weak blue glow of muons - particles that are formed as a result of collisions of neutrons with ice atoms and emit a weak blue glow.

Strings under the Amundsen-Scott station

Although the observatory is located onThe South Pole detectors collect data on cosmic neutrinos coming from all corners of the world, in particular from the northern hemisphere. At the same time, the Earth’s mass acts as a filter, cutting off “superfluous” or low-energy particles.

In 2014, scientists from the IceCube mission succeededprove that extragalactic neutrinos reach the earth. In the first three years of operation, the observatory recorded 37 neutrinos with an energy of more than 30 TeV, which is five times more than the energy of one proton.

In September 2017, scientists for the first time in historyrecorded neutrinos with an initial energy of 230 TeV. Thanks to data from the Fermi gamma telescope, astrophysicists have discovered a source of radiation, the blazer TXS 0506 + 056, located at a distance of 4 billion light years from Earth.

Well leading to the IceCube Observatory

These discoveries explain the importance of studying neutrinos.- these fundamental particles will allow scientists to explore cosmic bodies located at a distance of more than 13 billion light years. Outside this boundary, the space is filled with neutral hydrogen atoms, which absorb visible light, but neutrinos overcome this space freely.

Super-Kamiokande and SNO

IceCube is not the only neutrino observatory. At the end of the last century, scientists from the Super-Kamiokande and SNO projects received the Nobel Prize for discovering neutrino properties. Experiments on detectors based on the principle of fixing Cherenkov radiation showed that this fundamental particle has a nonzero mass.

Gravitational wave observatories

Space-time fluctuations detect verycomplicated. The fact is that such oscillations arising due to changes in the gravitational fields are very weak, they are not sensed by the senses and are not perceived by conventional instruments, unlike sound or a radio signal.

The existence of gravitational waves suggestedAlbert Einstein in his general theory of relativity. A theoretical physicist believed that the cause of such oscillations is the acceleration of mass in the Universe, for example, the merging or absorption of two large objects by each other. Waves allow you to determine the size of objects and the distance to them. Based on these data, scientists can recreate cosmic bodies before they collide.

For the first time in history, the gravitational wave succeededfix by scientists from the LIGO / VIRGO experiment collaboration - space-time oscillations have resulted from the merging of two black holes and the emergence of one supermassive rotating black hole.

The merger of two black holes

LIGO / Virgo

LIGO works on the principle of interferometer -The observatory consists of two shoulders 4 km long. At the beginning and at the end of each of them, ultratechnological mirrors are mounted on isolated vibration tables that move in the same plane. The rays of the laser in each of the shoulders move from the far point and unite in the center.

LIGO Observatory

The idea behind the experiment isin that the space-time distortion caused by the quadrupole gravitational wave would lead to a thin lengthening of one of the arms while simultaneously reducing the other. In other words, if one of the rays arrives with a slight delay, a signal is triggered, which may indicate the detection of a gravitational wave.

This elongation is extremely small - in September 2017LIGO physicists have noticed a shortening of the laser length in the arm by a trillionth of a meter - about one thousandth of the proton diameter. In addition, the difference in the time of arrival of the laser beams was only 10 ms.

Virgo works on the same principle and allowscheck the LIGO data. Now both projects are frozen indefinitely. To date, LIGO and its European partner Virgo have recorded a total of four gravitational waves - in 2015 and 2017.

Physicists expect that the study of gravitational waves will allow us to understand the causes of ultrafast rotation of neutron stars, to study the process of merging black holes.


Scientists from NASA and the European SpaceAgencies (ESA) are also working on a project of a gravitational-wave observatory in space - the eLISA antenna. The device, like LIGO, will work on the principle of an interferometer, but the laser beam will move between the mirrors at an astronomical distance. This will reduce the frequency of the waves perceived by the orbiter by four to five orders of magnitude compared to LIGO.

Now the project is at the design stage. The launch of the space antenna is scheduled for 2034, the estimated duration of the project is five to ten years.