Astrophysics: Most Read Articles


  1. standard gravitational parameter (μ) - a body's mass times the universal gravitational constant
  2. sigma-8 tension (S8 tension) - Lambda CDM anomaly regarding matter fluctuation
  3. Paschen series - hydrogen lines for electrons settling from n > 3 to n = 3
  4. M-type star (M) - spectral class of star with a temperature in the vicinity of 2500 K
  5. alpha process (α process) - synthesis of elements through alpha capture
  6. Brackett series - hydrogen lines for electrons settling from n > 4 to n = 4
  7. Hill radius - radius of gravitational influence of a body
  8. Fermi sea - atom's minimal-energy electrons filling its lower shells
  9. J2 - geopotential coefficient regarding a planet's oblateness
  10. Bethe-Heitler process - type of pair production interaction near nuclei
  11. astronomical symbol - traditional symbols specific to astronomy, for Sun, Earth, etc.
  12. Rayleigh-Jeans law - yields approximation of black-body curve useful at low frequencies
  13. dex - a number or ratio's log base 10
  14. Hellings and Downs curve - expected correlation in pulsar timing residuals from random waves
  15. BPT diagram - diagram comparing emission-line ratios for characterizing ionization
  16. wCDM - Big-Bang cosmological model with constant cosmological equation of state
  17. final parsec problem - lack of a convincing theory on how SMBHs can reach each other
  18. u-v plane - plane for displaying Fourier transforms of signal from the sky
  19. neutron degenerate matter - matter made up primarily of neutrons
  20. equilibrium temperature (Teq) - temperature a planet would have if it were an externally-heated black body
  21. ugriz photometric system - photometric system used for SDSS
  22. Gamow peak - relative speed most likely to cause atoms to fuse within a gas
  23. Tolman-Oppenheimer-Volkoff limit (TOV) - maximum mass of a neutron star
  24. e-folding time - time to increase by a factor of e
  25. dispersion measure (DM) - to what degree an EMR signal's lower frequencies are delayed
  26. Rosseland mean opacity - a useful weighted average of opacities at all the frequencies
  27. analytical methods - using solved equations rather than a lot of arithmetic
  28. Lyman break (LB) - abrupt change in galaxy spectrum at the Lyman series wavelength limit
  29. astronomical catalog - list of observed astronomical bodies including characteristics
  30. Balmer jump (BJ) - abrupt change in stellar spectrum at the Balmer series wavelength limit
  31. star formation rate (SFR) - rate at which material such as gas is turned into stars
  32. solar mass (MSun) - mass unit representing the mass of the Sun
  33. arcsecond (arcsec) - a 3600th of an angular degree
  34. radiation era - early-universe era when radiation pressure dominated
  35. epoch J2000.0 - noon 1/1/2000 GMT as used as a time reference
  36. Balmer series (H) - hydrogen lines for electrons settling from n > 2 to n = 2
  37. broad line region (BLR) - AGN region producing broader lines
  38. Jeans length - critical radius above which gravity will collapse a cloud
  39. electron degeneracy - electrons set free of atoms by the Pauli exclusion principle
  40. Korsch telescope - type of three-mirror reflector telescope
  41. Toomre Q parameter (Q) - stability criterion for differentially rotating disks
  42. Bondi radius - radius within which a body moving through a medium will draw it in
  43. gravitational wave strain (h) - a measure of the magnitude of a gravitational wave
  44. Alcock-Paczyński effect (AP effect) - type of distortion of the apparent depth of galaxy clusters
  45. Rydberg unit - unit of energy near 13.6 eV
  46. relativistic speed - a substantial fraction of the speed of light
  47. Mach number - ratio of flow-speed to sound-speed
  48. Balmer-break galaxy (BBG) - a galaxy emitting very little shorter than 3646 angstroms
  49. CO ladder - series of CO rotational spectral lines
  50. SH0ES - survey to increase the accuracy of the cosmic distance ladder
  51. Lick indices - defined set of spectral line indexes for stars
  52. optical depth (τ) - a measure of opaqueness of a path of light
  53. Salpeter timescale - timescale for black hole growth
  54. K-type star (K) - spectral class of star a bit cooler than the Sun
  55. Lambda-CDM model (ΛCDM) - Big-Bang cosmological model with a cosmological constant and cold dark matter
  56. halo orbit - type of orbit around an unstable Lagrangian point
  57. wavefront error (WFE) - measure of a class of telescope distortion
  58. number density (n) - number of objects per volume
  59. angular power spectrum - method of characterizing the CMB
  60. alpha-enhanced - metallicity with a high percentage of alpha elements
  61. plate scale - relation between angle and distance across an image
  62. Eddington bias - selection bias from mistaking something common for something rare
  63. relativistic invariance - quantity that remains the same regardless of frame of reference
  64. bolometric luminosity (LBol) - total luminosity of an object at all wavelengths
  65. line shape function - function describing the shape of a spectral line
  66. International Celestial Reference System (ICRS) - standardized variation of equatorial coordinate system
  67. Pfund series - hydrogen lines for electrons settling from n > 5 to n = 5
  68. metallicity (Z) - metal fraction of an object
  69. kappa mechanism (κ-mechanism) - stellar instability caused by opacity increasing with temperature
  70. gigayear (Gy) - a billion years
  71. galaxy main sequence - relation between galaxies' star formation and stellar mass
  72. main sequence fitting - cluster star distance determined through fitting with the H-R diagram
  73. tremendously low frequency (TLF) - presumably electromagnetic radiation, frequency below 3 Hz
  74. PHOENIX stellar model - computer model of a stellar photosphere
  75. surface of last scattering - sphere around us from which CMB photons are just reaching us
  76. carbon monoxide (CO) - compound of carbon and oxygen, one atom each
  77. column density - measure of the matter through which EMR is passing
  78. chirp mass (Mc) - a reduced-mass-like quantity that relates to gravitational waves
  79. gravitationally bound - description of objects kept together by gravity
  80. spaxel - like an image-pixel but with a SED for the location
  81. Lyman series (L) - hydrogen series from electrons settling from n > 1 to n = 1
  82. Kelvin-Helmholtz timescale (KH timescale) - time that would radiate away a body's heat energy given its luminosity
  83. double-line spectroscopic binary (SB2) - spectroscopic binary star where a specific line shows up at two different wavelengths
  84. specific intensity - intensity per unit wavelength or frequency
  85. line blanketing - so many bunched spectral lines that they cannot be distinguished
  86. LDN 1527 (L1527) - dark nebula in Taurus
  87. Strömgren sphere - sphere of ionized hydrogen around an OB star
  88. Lyot coronagraph (CLC) - original coronagraph design
  89. Limber approximation - formula approximating the density of galaxies in some direction
  90. ionization fraction - a substance's ratio of unattached electrons to nuclei
  91. spectral type - classification of stars based upon spectral features
  92. astronomical object - planet, star, galaxy, etc.
  93. moment of inertia factor - characterization of mass distribution within a planet
  94. transient astronomy - study of short-term astronomical phenomena
  95. Hayashi track - H-R diagram track of evolution of some pre-main-sequence stars
  96. mass-radius relation - model relating stellar mass and radius
  97. Bayer designation - star designation consisting of a Greek letter and constellation name
  98. local thermodynamic equilibrium (LTE) - state when temperature variation is too small to matter
  99. spectral energy distribution (SED) - function or plot of brightness at each wavelength in the spectrum
  100. O-type star (O) - star with spectral characteristics of above 30000 K

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