Milagro (the Spanish word for miracle) was a ground-based water

Cherenkov radiation Cherenkov radiation () is electromagnetic radiation emitted when a charged particle (such as an electron) passes through a dielectric medium (such as distilled water) at a speed greater than the phase velocity (speed of propagation of a wavefro ...

telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

situated in the

Jemez Mountains The Jemez Mountains (, Tewa: ''Tsąmpiye'ip'įn'', Navajo: ''Dził Łizhinii'') are a group of mountains in Rio Arriba, Sandoval, and Los Alamos counties, New Mexico, United States. Numerous Puebloan Indian tribes have lived in the Jemez Moun ...

near

Los Alamos, New Mexico Los Alamos (, meaning ''The Poplars'') is a census-designated place in Los Alamos County, New Mexico, United States, that is recognized as one of the development and creation places of the Nuclear weapon, atomic bomb—the primary objective of ...

at the Fenton Hill Observatory site. It was primarily designed to detect

gamma ray A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

s but also detected large numbers of

cosmic ray Cosmic rays or astroparticles 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 ...

s. It operated in the TeV region of the spectrum at an altitude of 2530 m. Like conventional telescopes, Milagro was sensitive to light but the similarities ended there. Whereas "normal" astronomical telescopes view the

universe The universe is all of space and time and their contents. It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of matter and energy, and the structures they form, from s ...

in visible light, Milagro saw the universe at very high energies. The light that Milagro saw was about 1 trillion times more energetic than visible light. While these particles of light, known as photons, are the same as the photons that make up visible light, they behave quite differently due to their high energies. A cosmic ray or high-energy gamma ray striking an atom in the upper atmosphere generates a cascade of particles known as an air shower. This cascade of particles are traveling near the

speed of light The speed of light in vacuum, commonly denoted , is a universal physical constant exactly equal to ). It is exact because, by international agreement, a metre is defined as the length of the path travelled by light in vacuum during a time i ...

and generate Cherenkov radiation as they pass through the atmosphere and the water in the Milagro experiment. The photons of Cherenkov radiation are detected by an array of detectors or

photomultiplier tubes Photomultiplier tubes (photomultipliers or PMTs for short) are extremely sensitive detectors of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum. They are members of the class of vacuum tubes, more spe ...

which send a signal to a recorder. The data from the recorder can then be used to determine the energy and direction of the cosmic or gamma ray. The Milagro experiment used 700 sensitive light detectors submerged in the pond plus another 200 detectors arrayed around the pond. The Milagro Experiment stopped taking data in April 2008 after seven years of operation. There is a follow-up experiment called the

High Altitude Water Cherenkov Experiment The High Altitude Water Cherenkov Experiment or High Altitude Water Cherenkov Observatory (also known as HAWC) is a gamma-ray and cosmic ray observatory located on the flanks of the Sierra Negra volcano in the Mexican state of Puebla at an alti ...

(HAWC) located near the

Large Millimeter Telescope The Large Millimeter Telescope (LMT) (, or GTM), officially the Large Millimeter Telescope Alfonso Serrano (), is the world's largest single-aperture telescope in its frequency range, built for observing radio waves in the wave lengths from app ...

at the

Sierra Negra Sierra Negra (also, and perhaps more properly, Cerro La Negra) is an extinct volcano located in the Mexico, Mexican state of Puebla, close to the border with Veracruz. At officially above sea level, it is the fifth-highest peak in Mexico. Sie ...

volcano,

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

, which is expected to be 15 times more sensitive. In November 2008 Milagro published the surprising result of observing cosmic ray anisotropy. The Milagro gamma-ray observatory laid the groundwork for the High-Altitude Water Cherenkov Observatory (HAWC) which has led to major discoveries. From the conservatory, researchers get an up-close look into the

Milky Way galaxy The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galaxy, which are ...

where they have detected the PeV gamma rays. These rays are among the highest-energy light ever observed (LANL, 2022).

Footnotes

External links

The Milagro Gamma-Ray Observatory, Los Alamos National Laboratory web archives (2009)The University of Maryland HAWC page
Cosmic-ray experiments Gamma-ray telescopes {{telescope-stub

See also

Footnotes

External links