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 lines 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 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.

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 having some unambiguous classification criteria remains convenient even if it is arbitrary.


(EMR,spectrum,band)
Further reading:
https://en.wikipedia.org/wiki/Xray
https://en.wikipedia.org/wiki/X-ray_astronomy
WaveLFreqPhoton
Energy
  
0.01nm30EHz124keVbeginX-ray
10nm30PHz124eVendX-ray

Referenced by pages:
active galaxy
AGILE
active galactic nucleus (AGN)
AGN corona
ALEXIS
Ariel 5
ASCA
ASTRO-H
ATHENA
atmospheric escape
AXIS
anomalous X-ray pulsar (AXP)
BeppoSAX
black hole binary (BHB)
binary star
black-body radiation
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
Cosmic Evolution Survey (COSMOS)
COUP
CubIXSS
cosmic X-ray background (CXB)
diffuse emission
detective quantum efficiency (DQE)
DQ Tau
Extended Chandra Deep Field-South Survey (ECDFS)
electromagnetic spectrum
electron shell
electromagnetic radiation (EMR)
eROSITA
EURECA
extreme ultraviolet (EUV)
electron volt (eV)
EXOSAT
eXTP
filter
fossil group
frequency
galaxy cluster (CL)
gamma rays (GR)
Ginga
grazing incidence optics (GIO)
GRANAT
grating
GRS 1915+105
hardness
high-B radio pulsar (HBRP)
high-energy astrophysics (HEA)
HEAO-1
HEAO-2
HEASARC
High Energy Transient Explorer (HETE)
HXMT
International Cometary Explorer (ICE)
intracluster medium (ICM)
intergalactic medium (IGM)
INTEGRAL
ionizing radiation
ionosphere
IRAS 13224-3809
Japan Aerospace Exploration Agency (JAXA)
KID
K-line
Kramers opacity law
Lynx
M82
Massive Cluster Survey (MACS)
magnetar
Mars 2020
MAXI
Mars Exploration Rover (MER)
microcalorimeter
microchannel array
Mars Pathfinder (MPF)
Mars Science Laboratory (MSL)
millisecond pulsar (MSP)
MIT X-ray Burst Source Catalog (MXB)
N 103B
NEAR Shoemaker (NEAR)
neutron star (NS)
NICER
nova (N)
NuSTAR
Orbiting Astronomical Observatory (OAO)
obscured fraction-luminosity relation
OSO 7
Penrose Compton scattering (PCS)
photocathode
photodissociation
photon energy
pre-main-sequence star (PMS)
planetary nebula (PN)
pulsar (PSR)
Puppis A
pulsar wind nebula (PWN)
quasi-periodic oscillation (QPO)
Rosat Bright Survey (RBS)
Rho Ophiuchi Cloud Complex
Rosat Hard Survey (RHS)
Rosalind Franklin
ROSAT
Rosetta
rp-process
radio source (RS)
RXTE
scintillator
Spitzer Extragalactic Representative Volume Survey (SERVS)
soft gamma repeater (SGR)
slew survey
SMART-1
Solar Maximum Mission (SMM)
Solar Orbiter (SolO)
spectral line designation
spectrograph
spectrometer
spectroscope
Spektr-RG (SRG)
SS 433
STAR-X
stellar-mass black hole
superconducting tunnel junction (STJ)
Sun
Sun surface features
Suzaku
Swift
Subaru XMM-Newton Deep Survey (SXDS)
Taurus-Auriga Complex (Tau-Aur Complex)
TD-1A
tidal disruption event (TDE)
telescope type
thermal bremsstrahlung
Thomson optical depth (τT)
3C 279
3C 295
3C 9
transient
ultra-fast outflow (UFO)
Uhuru
ultraviolet (UV)
ultraluminous X-ray source (ULX)
Ulysses
ultraviolet astronomy
Vela supernova remnant
wavelength
Wien's displacement law
Wolf-Rayet star
Wolter telescope
XBONG
XEUV
X-ray luminosity function (XLF)
X-ray luminous galaxy cluster
XMM-Newton
X-ray burster (XRB)
X-ray source
XRISM
XTP
Yohkoh

Index