Through gamma rays, scientists detected a small satellite galaxy filled with dark matter

By | 07/09/2022

Illustration of a gamma ray on the electromagnetic spectrum

detail of an all-sky color map of gamma ray sources in the night sky.  A large bright area of gamma ray sources from the Milky Way galaxy stretch across the center.

Brighter colors in the Cygus region indicate greater numbers of gamma rays detected by the Fermi gamma-ray space telescope. Credit: NASA/DOE/International LAT Team


Gamma rays have the smallest wavelengths and the most free energy of any wave in the electromagnetic spectrum. They are produced by the hottest and almost energetic objects in the universe, such as neutron stars and pulsars, supernova explosions, and regions around blackness holes. On Earth, gamma waves are generated past nuclear explosions, lightning, and the less dramatic activeness of radioactive decay.


Different optical lite and x-rays, gamma rays cannot be captured and reflected past mirrors. Gamma-ray wavelengths are and then short that they tin laissez passer through the space within the atoms of a detector. Gamma-ray detectors typically contain densely packed crystal blocks. Every bit gamma rays pass through, they collide with electrons in the crystal. This process is called Compton scattering, wherein a gamma ray strikes an electron and loses energy, like to what happens when a cue ball strikes an eight ball. These collisions create charged particles that can be detected past the sensor.

This diagram shows how a photon from incoming energy hits an electron at rest. The photon scatters and the electron recoils at the same angle in the opposite direction.


Gamma-ray bursts are the well-nigh energetic and luminous electromagnetic events since the Large Bang and can release more energy in 10 seconds than our Lord’s day volition emit in its entire 10-billion-year expected lifetime! Gamma-ray astronomy presents unique opportunities to explore these exotic objects. By exploring the universe at these high energies, scientists can search for new physics, testing theories and performing experiments that are not possible in World-leap laboratories.

If we could meet gamma rays, the night sky would look strange and unfamiliar. The familiar view of constantly shining constellations would be replaced past always-changing bursts of loftier-energy gamma radiation that concluding fractions of a second to minutes, popping like cosmic flashbulbs, momentarily dominating the gamma-ray sky and so fading.

NASA’s Swift satellite recorded the gamma-ray boom caused by a blackness pigsty being born 12.viii billion light years abroad (below). This object is among the most afar objects ever detected.

An image of a gamma ray burst seen in gamma rays on left show s a bright burst of yellow, orange and red. The image on the right shows the same burst in visible and Ultraviolet as just a bright star in the center with some slight red and green coloring surrounding the star.

Credit: NASA/Swift/Stefan Immler, et al.


Scientists can use gamma rays to decide the elements on other planets. The Mercury Surface, Space Surroundings, Geochemistry, and Ranging (MESSENGER) Gamma-Ray Spectrometer (GRS) can mensurate gamma rays emitted by the nuclei of atoms on planet Mercury’s surface that are struck by cosmic rays. When struck by cosmic rays, chemical elements in soils and rocks emit uniquely identifiable signatures of free energy in the form of gamma rays. These information tin help scientists look for geologically important elements such as hydrogen, magnesium, silicon, oxygen, atomic number 26, titanium, sodium, and calcium.

The gamma-ray spectrometer on NASA’s Mars Odyssey Orbiter detects and maps these signatures, such equally this map (below) showing hydrogen concentrations of Martian surface soils.

A color map of Mars showing the distribution of hydrogen by mapping the lower-limit of water mass fraction.

Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio


Gamma rays besides stream from stars, supernovas, pulsars, and black hole accretion disks to wash our sky with gamma-ray light. These gamma-ray streams were imaged using NASA’due south Fermi gamma-ray space telescope to map out the Milky Manner galaxy by creating a full 360-caste view of the galaxy from our perspective here on World.

an all-sky color map of gamma ray sources in the night sky.  A large bright area of gamma ray sources from the Milky Way galaxy stretch across the center.

Credit: NASA/DOE/International LAT Team


The composite prototype below of the Cas A supernova remnant shows the full spectrum in one image. Gamma rays from Fermi are shown in magenta; ten-rays from the Chandra Observatory are blue and dark-green. The visible light data captured by the Hubble space telescope are displayed in yellow. Infrared data from the Spitzer space telescope are shown in red; and radio data from the Very Big Array are displayed in orange.

A multi-sensor composite image of a supernova. A multicolored image of gas and dust with an area highlighted showing GeV gamma-ray source.

Credit: NASA/DOE/Fermi LAT Collaboration, CXC/SAO/JPL-Caltech/Steward/O. Krause et al., and NRAO/AUI

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National Aeronautics and Infinite Assistants, Scientific discipline Mission Advisers. (2010). Gamma Rays. Retrieved
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Science Mission Directorate. “Gamma Rays”
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