A Centauro event is a kind of anomalous event observed in

cosmic-ray detector Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...

s since 1972. They are so named because their shape resembles that of a centaur: i.e., highly asymmetric. If some versions of string theory are correct, then high-energy

cosmic ray Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...

s could create black holes when they collide with

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...

s in the

Earth's atmosphere The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing fo ...

. These black holes would be tiny, with a

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...

of around 10

microgram In the metric system, a microgram or microgramme is a unit of mass equal to one millionth () of a gram. The unit symbol is μg according to the International System of Units (SI); the recommended symbol in the United States and United Kingdom whe ...

s. They would also be unstable enough to explode in a burst of

particle In the physical sciences, a particle (or corpuscule in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass. They vary greatly in size or quantity, from ...

s within around 10⁻²⁷ seconds. Theodore Tomaras, a

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

at the

University of Crete The University of Crete (UoC; Greek: Πανεπιστήμιο Κρήτης) is a multi-disciplinary, research-oriented institution in Crete, Greece, located in the cities of Rethymno (official seat) and Heraklion, and one of the country's most aca ...

Heraklion Heraklion or Iraklion ( ; el, Ηράκλειο, , ) is the largest city and the administrative capital of the island of Crete and capital of Heraklion regional unit. It is the fourth largest city in Greece with a population of 211,370 (Urban Ar ...

Greece Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders ...

, and his

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eig ...

n collaborators hypothesize that these miniature black holes could explain certain anomalous observations made by

cosmic-ray Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...

detectors in the Bolivian

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

and on a mountain in

Tajikistan Tajikistan (, ; tg, Тоҷикистон, Tojikiston; russian: Таджикистан, Tadzhikistan), officially the Republic of Tajikistan ( tg, Ҷумҳурии Тоҷикистон, Jumhurii Tojikiston), is a landlocked country in Centr ...

. In 1972, the Andean detector registered a cascade that was strangely rich in charged, quark-based particles; far more particles were detected in the bottom portion of the detector than in the top portion. In years since, the detectors in Bolivia and

have detected more than 40 Centauro events. Various explanations have been suggested. One possible explanation might be if the

strong force The strong interaction or strong force is a fundamental interaction that confines quarks into proton, neutron, and other hadron particles. The strong interaction also binds neutrons and protons to create atomic nuclei, where it is called the ...

between particles behaves unusually when they have extremely high energies. Exploding black holes are also a possibility. The team calculated what signal a detector would register if a cosmic ray creates a miniature black hole that explodes nearby. The researchers' prediction is consistent with the observed Centauro events. The Tomaras team hopes that computer simulations of mini-black holes exploding, and further observations, will solve the puzzle.

Solution to the Centauro puzzle

In 2003 an international team of researches from

and Japan found out that the mysterious observation from mountain-top cosmic ray experiments can be explained with conventional physics. The new analysis of Centauro I reveals that there is a difference in the arrival angle between the upper block and lower block events, so the two are not products of the same interaction. That leaves only the lower chamber data connected to the Centauro I event. In other words, the man-horse analogy becomes redundant. There is only an obvious "tail", and no "head". The original detector setup had gaps between neighboring blocks in the upper chamber. Linear dimensions of gaps were comparable to the geometrical size of the event. The signal observed in the lower detector was similar to an ordinary interaction occurred at low altitude above the chamber, thus providing a natural solution: passing of a cascade of particles through a gap between the upper blocks. In 2005 it was shown that "other Centauro events" can be explained by peculiarities of the Chacaltaya detector. So-called "exotic signal" observed so far in cosmic ray experiments using a traditional X-ray emulsion chamber detector can be consistently explained within the framework of standard

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...

Solution to the Centauro puzzle

Further reading