An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A process going on in a molecular cloud surface whereby the surface material ionized by ultraviolet photons of neighboring stars is dissipated.

→ photo- + → evaporation.

The mechanism of raising an electron to higher energies by photon absorption, when the energy of the photon is too low to cause photoionization.

→ photo- + → excitation.

A picture produced by photography. → picture.

From → photo- + → -graph.

Aks, from Ar. 'aks "to inverse, reverse." Šidnegâr, nurnegâr, from šid, nur, → photo-, + negâr, → graph.

The apparent magnitude of a star as determined by measuring its brightness on a photographic plate. The photographic magnitude scale is now considered obsolete.

Adj. of → photography; → magnitude.

Recording a large area of the night sky by photographic techniques, as practiced in the past before the advent of electronic detectors.

Adj. of → photography; → survey.

The process of recording and producing images by exposing light-sensitive detectors to light or other forms of radiation.

→ photo-, → -graphy.

Aksbardâri, literally "taking photograph," from aks, → photograph, + bardâri verbal noun of bardâštan "to take," composite verb from bar- "on; up; upon; in; into; at; forth; with; near; before; according to" (Mid.Pers. abar; O.Pers. upariy "above; over, upon, according to;" Av. upairi "above, over," upairi.zəma- "located above the earth;" cf. Gk. hyper- "over, above;" L. super-; O.H.G. ubir "over;" PIE base *uper "over") + dâštan "to have, to possess" (Mid.Pers. dâštan; O.Pers./Av. root dar- "to hold, keep back, maintain, keep in mind;" cf. Skt. dhr-, dharma- "law;" Gk. thronos "elevated seat, throne;" L. firmus "firm, stable;" Lith. daryti "to make;" PIE *dher- "to hold, support").
Šidnegâri, nurnegâri, action noun from šidnegâr, nurnegâr, → photograph.

The physical process in which an incident high-energy photon ejects one or more electrons from an atom, ion, or molecule.

→ photo- + → ionization.

To cause, or to undergo → photoionization.

→ photo-; → ionize.

Subject to, or produced by → photoionization.

→ photo-; → ionized.

A process in which → absorption of photons at → ultraviolet (UV) / → optical wavelengths is followed by → electronic transitions associated with the emission of longer wavelength optical and → near-IR photons. Photoluminescence has two types: → phosphorescence and → luminescence. The excitation of the photoluminescence process under astrophysical conditions results from the absorption of a single UV/optical photon, leading to an electronic transition from a → ground state (1) to a higher state (2). State (2) typically is a bound, high-lying vibrational-rotational level of the first or second electronically excited state of a molecule or molecular ion, or a high state in the → conduction band of a semiconductor particle. The excited system relaxes through a series of → vibrational-rotational transitions until the electron finds itself in an intermediate state (3), from where an optical electronic transition back to the ground state (1) is possible. In a → polycyclic aromatic hydrocarbon (PAH) molecule, for example, state (3) can either be the lowest state in the → singlet or → triplet vibrational-rotational manifold of the first excited electronic level (Witt, A. N., Vijh, U. P., 2003, astro-ph/0309674).

→ photo-; → luminescence.

An instrument for measuring the amount of light.

→ photo- + → -metry.

Pertaining to or related to → photometry.

→ photometer + → -ic.

The range of → wavelengths allowed by a → filter used in a → photometric system.

→ photometric + → band.

A binary star whose binarity is detectable from its variability and light-curve that has certain specific characteristics.

→ photometric + → binary.

A calibration which converts the measured relative magnitudes into an absolute photometry.

→ photometric + → calibration.

A method of deriving the distance of a star using its → apparent magnitude and the → absolute magnitude inferred from its → spectral type.

This is a misnomer, because the method has nothing to do with parallax; → photometric; → parallax.

A system of → magnitudes, each of them characterized by a set of well-defined → passbands (or → filters) with known → response curves. The system is defined by the values given for the → standard stars. See also:
→ AB magnitude system, → five-color system, → Stromgren system, → JHK system, → UBV system, → uvby system.

→ photometric; → system.

In astronomy, the measurement of the light of astronomical objects, generally in the visible or infrared bands, in which a wavelength band is normally specified.

→ photo- + → -metry.

Electronic tube which converts photons into electrons, multiplies the electrons via a series of electrodes, and produces a measurable current from a very small input signal.

→ photo- + → multiplier.

The → quantum of the → electromagnetic field, which mediates the interaction between charged particles. It is the mass-less → boson with zero → electric charge, which propagates with the → speed of light in vacuum. The energy of a photon is connected to its → frequency ν, through the formula E = hν, where h is → Planck's constant.

From phot-, variant of → photo- before a vowel + → -on a suffix used in the names of subatomic particles (gluon; meson; neutron), quanta (photon, graviton), and other minimal entities or components. The term photon was coined by Gilbert N. Lewis in 1926 in a letter to the editor of Nature magazine (Vol. 118, Part 2, December 18, page 874).