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. astronomical symbol - traditional symbols specific to astronomy, for Sun, Earth, etc.
  4. Paschen series - hydrogen lines for electrons settling from n > 3 to n = 3
  5. M-type star (M) - spectral class of star with a temperature in the vicinity of 2500 K
  6. Hill radius - radius of gravitational influence of a body
  7. alpha process (α process) - synthesis of elements through alpha capture
  8. Bethe-Heitler process - type of pair production interaction near nuclei
  9. J2 - geopotential coefficient regarding a planet's oblateness
  10. Brackett series - hydrogen lines for electrons settling from n > 4 to n = 4
  11. Fermi sea - atom's minimal-energy electrons filling its lower shells
  12. dex - a number or ratio's log base 10
  13. Rayleigh-Jeans law - yields approximation of black-body curve useful at low frequencies
  14. Hellings and Downs curve - expected correlation in pulsar timing residuals from random waves
  15. wCDM - Big-Bang cosmological model with constant cosmological equation of state
  16. Rosseland mean opacity - a useful weighted average of opacities at all the frequencies
  17. equilibrium temperature (Teq) - temperature a planet would have if it were an externally-heated black body
  18. Pioneer - NASA program for solar-system exploration
  19. Tolman-Oppenheimer-Volkoff limit (TOV) - maximum mass of a neutron star
  20. M94 - nearby dusty galaxy
  21. ugriz photometric system - photometric system used for SDSS
  22. u-v plane - plane for displaying Fourier transforms of signal from the sky
  23. CO ladder - series of CO rotational spectral lines
  24. Gamow peak - relative speed at which the largest number of nuclei fuse within a gas
  25. Balmer series (H) - hydrogen lines for electrons settling from n > 2 to n = 2
  26. star formation rate (SFR) - rate at which material such as gas is turned into stars
  27. neutron degenerate matter - matter made up primarily of neutrons
  28. final parsec problem - lack of a consensus theory on how SMBHs can reach each other
  29. astronomical catalog - list of observed astronomical bodies including characteristics
  30. arcsecond (arcsec) - a 3600th of an angular degree
  31. BPT diagram - diagram comparing emission-line ratios for characterizing ionization
  32. e-folding time - time to increase by a factor of e
  33. Jeans length - critical radius above which gravity will collapse a cloud
  34. dispersion measure (DM) - to what degree an EMR signal's lower frequencies are delayed
  35. Hooker Telescope - 2.54-m reflector telescope in California
  36. broad line region (BLR) - AGN region producing broader lines
  37. gravitational wave strain (h) - a measure of the magnitude of a gravitational wave
  38. solar mass (MSun) - mass unit representing the mass of the Sun
  39. Balmer jump (BJ) - abrupt change in stellar spectrum at the Balmer series wavelength limit
  40. analytical methods - using solved equations rather than a lot of arithmetic
  41. spectral type - classification of stars based upon spectral features
  42. Lyman break (LB) - abrupt change in galaxy spectrum at the Lyman series wavelength limit
  43. epoch J2000.0 - noon 1/1/2000 GMT as used as a time reference
  44. Toomre Q parameter (Q) - stability criterion for differentially rotating disks
  45. electron degeneracy - electrons set free of atoms by the Pauli exclusion principle
  46. SH0ES - survey to increase the accuracy of the cosmic distance ladder
  47. Alcock-Paczyński effect (AP effect) - type of distortion of the apparent depth of galaxy clusters
  48. Korsch telescope - type of three-mirror reflector telescope
  49. radiation era - early-universe era when radiation pressure dominated
  50. mass-radius relation - model relating stellar mass and radius
  51. Bondi radius - radius within which a body moving through a medium will draw it in
  52. Lambda-CDM model (ΛCDM) - Big-Bang cosmological model with a cosmological constant and cold dark matter
  53. Salpeter timescale - timescale for black hole growth
  54. metallicity (Z) - metal fraction of an object
  55. bolometric luminosity (LBol) - total luminosity of an object at all wavelengths
  56. relativistic speed - a substantial fraction of the speed of light
  57. interstellar object - body not bound to the solar system
  58. Lick indices - defined set of spectral line indexes for stars
  59. Eddington bias - selection bias from mistaking something common for something rare
  60. Balmer-break galaxy (BBG) - a galaxy emitting very little shorter than 3646 angstroms
  61. K-type star (K) - spectral class of star a bit cooler than the Sun
  62. Rydberg unit - unit of energy near 13.6 eV
  63. H-beta (Hβ) - hydrogen line for electrons settling from n = 4 to n = 2
  64. KM3-230213A - extremely energetic neutrino from space detected in 2023
  65. Mach number - ratio of flow-speed to sound-speed
  66. w0waCDM - particular parameterized Big-Bang cosmological model
  67. PHOENIX stellar model - computer model of a stellar photosphere
  68. optical depth (τ) - a measure of opaqueness of a path of light
  69. chirp mass (Mc) - a reduced-mass-like quantity that relates to gravitational waves
  70. wavefront error (WFE) - measure of a class of telescope distortion
  71. angular power spectrum - method of characterizing the CMB
  72. gigayear (Gy) - a billion years
  73. relativistic invariance - quantity that remains the same regardless of frame of reference
  74. plate scale - relation between angle and distance across an image
  75. number density (n) - number of objects per volume
  76. halo orbit - type of orbit around an unstable Lagrangian point
  77. M31-2014-DS1 - bright star in M31 that disappeared
  78. kappa mechanism (κ-mechanism) - stellar instability caused by opacity increasing with temperature
  79. alpha-enhanced - metallicity with a high percentage of alpha elements
  80. SPT2349-56 - early galaxy cluster with high star formation
  81. 2I/Borisov - interstellar comet spotted in 2019
  82. STMAG system - absolute monochromatic magnitude calibration used for HST
  83. galaxy main sequence - relation between galaxies' star formation and stellar mass
  84. line shape function - function describing the shape of a spectral line
  85. International Celestial Reference System (ICRS) - standardized variation of equatorial coordinate system
  86. column density - measure of the matter through which EMR is passing
  87. carbon monoxide (CO) - compound of carbon and oxygen, one atom each
  88. Lyman series (L) - hydrogen series from electrons settling from n > 1 to n = 1
  89. double-line spectroscopic binary (SB2) - spectroscopic binary star where a specific line shows up at two different wavelengths
  90. Pfund series - hydrogen lines for electrons settling from n > 5 to n = 5
  91. tremendously low frequency (TLF) - presumably electromagnetic radiation, frequency below 3 Hz
  92. spaxel - like an image-pixel but with a SED for the location
  93. main sequence fitting - cluster star distance determined through fitting with the H-R diagram
  94. surface of last scattering - sphere around us from which CMB photons are just reaching us
  95. Kelvin-Helmholtz timescale (KH timescale) - time that would radiate away a body's heat energy given its luminosity
  96. nuclear statistical equilibrium (NSE) - equilibrium of nuclei emitting and absorbing particles
  97. moment of inertia factor - characterization of mass distribution within a planet
  98. cosmological time dilation - very distant events appear to take longer
  99. Strömgren sphere - sphere of ionized hydrogen around an OB star
  100. gravitationally bound - description of objects kept together by gravity
Index