Astrophysics (Index)About

X-ray

(electromagnetic radiation, wavelength 0.01 to 10 nanometers)

The term X-ray generally refers to electromagnetic radiation (EMR) with a wavelength within the range of 0.01-10 nm, lying between ultraviolet and gamma rays. Lower energy/frequency X-rays, toward the ultraviolet end, are termed soft and higher energy/frequency, toward the gamma rays end are termed hard. Intervening thresholds chosen to distinguish soft and hard are typically in the general region of 0.1-0.2 nm or 5-10 keV. Rather than by frequency or wavelength, X-rays are often cited by photon energy, in electron volts (eV). The equivalent to the above-cited range for X-rays is 124 eV to 124 keV, but astronomers often cite the line between X-rays and gamma rays as 100 keV: this difference is largely moot as in discussions of this EMR, a specific photon-energy range of interest is likely to be stated.

The phrase cosmic X-ray survey has been used for surveys of X-ray sources at cosmological distances, e.g., distant active galactic nuclei (AGNs).

There is not a consensus across all sciences and industries on the boundaries of EMR termed X-rays, especially between X-rays and gamma rays for which the distinction originally arose from what produced them: X-rays were from high-voltage vacuum tubes producing cathode rays, and gamma rays are a type of emission occurring during radioactive decay of radioactive substances such as radium. However, both these types of sources are producing EMR, and the respective wavelength ranges overlap, an example of the fact that mechanisms that produce EMR don't adhere to any particular absolute limits. In astronomical observation, any possible boundary would still be spanned by some instruments and some sources, but using some unambiguous classification-criteria is convenient even if it is arbitrary.

X-rays from space (like gamma rays) are virtually blocked by Earth's atmosphere, helping make Earth habitable, and X-ray telescopes are space-based. Among the telescopes/observatories:


(EMR,spectrum,band)
Further reading:
https://en.wikipedia.org/wiki/Xray
https://en.wikipedia.org/wiki/X-ray_astronomy
http://hyperphysics.phy-astr.gsu.edu/hbase/ems3.html#c4
https://astronomy.swin.edu.au/cosmos/X/X-rays
https://www.britannica.com/science/X-ray
WaveLFreqPhoton
Energy
  
0.01nm30EHz124keVbeginX-ray
10nm30PHz124eVendX-ray

Referenced by pages:
3C 279
3C 295
3C 9
active galactic nucleus (AGN)
active galaxy
Aditya-L1
AGILE
AGN corona
ALEXIS
Arcus
Ariel 5
ASCA
AstroSat
AT2019dsg
ATHENA
atmospheric escape
Auger effect
AXIS
BASS
BeppoSAX
binary star
black hole binary (BHB)
black-body radiation
Capella
Chandra Deep Field North (CDFN)
Chandra Deep Field South (CDFS)
Chandra X-ray Observatory (CXO)
color-magnitude diagram (CMD)
Compton reflection
Compton scattering
cooling flow
coronal loop
Cosmic Evolution Survey (COSMOS)
cosmic X-ray background (CXB)
COUP
CubIXSS
detective quantum efficiency (DQE)
diffuse emission
DQ Tau
dust echo
Einstein Probe (EP)
Einstein Telescope (ET)
electromagnetic radiation (EMR)
electromagnetic spectrum
electron shell
electron volt (eV)
eROSITA
escape fraction
EURECA
EXOSAT
Extended Chandra Deep Field-South Survey (ECDFS)
eXTP
extreme ultraviolet (EUV)
filter
fossil group
frequency (ν)
galaxy cluster (CL)
gamma rays (GR)
Gamow Explorer
gas pixel detector (GPD)
Ginga
GRANAT
grating
grazing incidence optics (GIO)
GRS 1915+105
hardness
HEAO-1
HEAO-2
HEASARC
High Energy Transient Explorer (HETE)
high-B radio pulsar (HBRP)
high-energy astrophysics (HEA)
Hitomi
HXMT
imaging spectrometer
INTEGRAL
intergalactic medium (IGM)
International Cometary Explorer (ICE)
ionizing radiation
ionosphere
IRAS 13224-3809
IXPE
Japan Aerospace Exploration Agency (JAXA)
K-line
Kepler-Swift Active Galaxies and Stars Survey (KSwAGS)
KID
Kramers opacity law
Kvant 1
Lyman continuum (LyC)
Lynx
magnetar
Mars 2020
Mars Exploration Rover (MER)
Mars Pathfinder (MPF)
Mars Science Laboratory (MSL)
Massive Cluster Survey (MACS)
MAXI
MESSENGER
microcalorimeter
microchannel array
millisecond pulsar (MSP)
MIT X-ray Burst Source Catalog (MXB)
N 103B
NEAR Shoemaker (NEAR)
neutron star (NS)
NICER
nova (N)
NuSTAR
obscured fraction-luminosity relation
optics
Orbiting Astronomical Observatory (OAO)
OSO 7
OSO 8
panchromatic
Penrose Compton scattering (PCS)
Perseus Cluster (Abell 426)
photocathode
photodissociation
photon energy
planetary nebula (PN)
proportional counter
pulsar (PSR)
pulsar wind nebula (PWN)
Puppis A
quasi-periodic oscillation (QPO)
radio source (RS)
rare designator prefixes
Rosalind Franklin
ROSAT
Rosat Bright Survey (RBS)
Rosetta
RXTE
Satech-01
scintillator
SELENE
Sgr B2
slew survey
Small Astronomy Satellite 3 (SAS 3)
SMART-1
soft gamma repeater (SGR)
Solar Maximum Mission (SMM)
Solar Orbiter (SolO)
spectral line designation
spectrograph
spectrometer
spectroscope
Spektr-RG (SRG)
Spitzer Extragalactic Representative Volume Survey (SERVS)
STAR-X
stellar-mass black hole (stellar-mass BH)
StrayCats
STROBE-X
Subaru XMM-Newton Deep Survey (SXDS)
Sun
Sun surface features
Sunyaev-Zel'dovich effect (SZ effect)
superconducting tunnel junction (STJ)
Suzaku
SWFO-L1
Swift
synchrotron self-Compton (SSC)
Taurus-Auriga Complex (Tau-Aur Complex)
TD-1A
telescope type
thermal bremsstrahlung
THESEUS
Thomson optical depth (τT)
tidal disruption event (TDE)
transient (AT)
Uhuru
ultra-fast outflow (UFO)
ultraluminous X-ray source (ULX)
ultraviolet (UV)
ultraviolet astronomy
Ulysses
Vela
Vela supernova remnant
wavelength (λ)
Wien's displacement law
Wolf-Rayet star
Wolter telescope
X-ray binary (XRB)
X-ray burster (XRB)
X-ray flash (XRF)
X-ray luminosity function (XLF)
X-ray luminous galaxy cluster
X-ray pulsar
X-ray source
XBONG
XEUV
XMM-Newton
XRISM
XTP
Yohkoh

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