Astrophysics (Index)About

gamma rays

(GR)
(electromagnetic radiation, wavelength 10 picometers and less)

Gamma rays (GRs) consists of electromagnetic radiation (EMR) with extremely short wavelengths, one criteria being any with a wavelength of 0-10 pm. In the electromagnetic spectrum, they include everything beyond X-rays in frequency and photon energy. They are generally the result of nuclear reactions, and are present in cosmic rays. They are often specified by their photon energy in electron volts (eV), as opposed to using their frequency or wavelength. Equivalent to the above-cited wavelength-range is "everything beyond 124 keV", but astronomers often cite the line between X-rays and gamma rays as 100 keV (i.e., a round number of eV): this discrepancy is largely moot because discussions of EMR in the 100-124 keV photon-energy range, the energy of interest is likely to be stated.

There is no consensus across all scientists/technologists on the boundary between EMR termed X-rays and gamma rays: the distinction originally arose from the manner in which they are produced: X-rays were from high-voltage vacuum tubes producing cathode rays, and gamma rays are one type of emission occurring during radioactive decay, of radioactive substances such as radium. However, both these types of emissions consist of EMR, and the wavelength ranges from these two sources overlap. Any fixed boundary is arbitrary: mechanisms that produce this short-wavelength EMR don't completely adhere to such absolute limits, and regarding astronomical observation, there will be particular instruments and sources that span any particular chosen boundary.

The targets of gamma-ray astronomy include gamma-ray transients (gamma-ray bursts, GRBs) and a gamma-ray background (cosmic gamma ray background as well as a galactic gamma ray background due to the interaction of cosmic rays with the interstellar medium) as well as gamma-ray sources, such as the Crab Nebula.

Gamma rays from space (like X-rays) are virtually blocked by Earth's atmosphere, which helps make Earth habitable, and gamma-ray telescopes are either space-based or are designed to sense the results of gamma-ray interactions with the atmosphere (Cherenkov detectors). Among the space telescopes/observatories:

Ground detectors:


(EMR,spectrum,band)
Further reading:
https://en.wikipedia.org/wiki/Gamma_ray
https://en.wikipedia.org/wiki/Gamma-ray_astronomy
http://hyperphysics.phy-astr.gsu.edu/hbase/ems3.html#c5
WaveLFreqPhoton
Energy
  
0pminfinfbegingamma rays
10pm30EHz124keVendgamma rays

Referenced by pages:
3C 279
active galactic nucleus (AGN)
active galaxy
AGILE
air shower
ARGO-YBJ Experiment
BASS
BeppoSAX
Bethe-Heitler process
black-body radiation
Cherenkov detector
Cherenkov radiation
Cherenkov Telescope Array (CTA)
CNO cycle
Compton Gamma Ray Observatory (CGRO)
Compton scattering
Compton telescope
Cos-B
COSI
cosmic gamma ray background (CGB)
curvature radiation
Dawn
Dragonfly (NF4)
electromagnetic radiation (EMR)
electromagnetic spectrum
electron volt (eV)
escape fraction
Fermi (FGST)
Fermi bubbles
Fred Lawrence Whipple Observatory (FLWO)
frequency (ν)
gamma-ray burst (GRB)
GRANAT
habitable zone (HZ)
hardness
HEAO-1
HEASARC
High Energy Stereoscopic System (HESS)
High-altitude Water Cherenkov Observatory (HAWC)
high-energy astrophysics (HEA)
Hitomi
imaging spectrometer
INTEGRAL
intensity interferometer
ionizing radiation
Kvant 1
LHAASO
Lunar Prospector
Lyman continuum (LyC)
MAGIC
magnetar
Mars Observer (MO)
Mars Odyssey
MESSENGER
Milagro
millisecond pulsar (MSP)
MMX
NEAR Shoemaker (NEAR)
neon burning
neutron spectrometer
nova (N)
nuclear statistical equilibrium (NSE)
nucleosynthesis
nuclide
observational astronomy
OSO 7
pair production
pair telescope
panchromatic
Penrose Compton scattering (PCS)
photodisintegration
photodissociation
photon energy
potassium/thorium ratio (K/Th ratio)
Psyche
radio source (RS)
radioactive decay
radioactive heating
radioactivity
rare designator prefixes
Roque de los Muchachos Observatory (ORM)
scintillator
SELENE
Sgr B2
Small Astronomy Satellite 2 (SAS 2)
soft gamma repeater (SGR)
Solar Maximum Mission (SMM)
source
spark chamber
Swift
synchrotron self-Compton (SSC)
TD-1A
telescope type
THESEUS
tidal disruption event (TDE)
triple alpha process
Tunka experiment
ultra-high-energy gamma rays (UHEGR)
Vela
VERITAS
VERITAS
very-high-energy gamma rays (VHEGR)
VHE
wavelength (λ)
Wind
X-ray
X-ray flash (XRF)

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