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

Occurring or appearing again, especially repeatedly or periodically (Dictionary.com). → recurrence nova.

Verbal adj. from → recur.

A → cataclysmic variable star that undergoes → outbursts similar to those found in novae.

→ recurrent; → nova.

1) A running backward, return.
2) Math.: A process in which objects are defined by the repeated application of a rule or algorithm.

From L. recursionem (nominative recursio); → recurrent.

Bâzâneš, verbal noun of bâzâmadan, → recur.

1) Pertaining to or using a rule or procedure that can be applied repeatedly.
2) Math.: Pertaining to or using the process of → recursion.

Adjective from → recursion.

Math.: A definition of a function from which values of the same function can be calculated in a finite number of steps. In mathematical logic and computer science, a recursive definition is used to define an object in terms of itself. An example is the → factorial: n! = n*(n-1)!

→ recursive; → definition.

1) To treat or process used material so that it can be used again.
2) To repeat or pass through a process again. → recycled pulsar.

→ re-; → cycle.

A → pulsar of abnormally low magnetic field and short period. The short period suggests that the pulasr is young, while the low field suggests a very old pulsar. According to theoretical models, a pulsar at some point in its evolution stops functioning as a pulsar. If it resides in a binary system (→ binary pulsar), its magnetic field decays in the interval when the companion evolves and fills its → Roche lobe. The dead pulsar is eventually spun up to life when → mass transfer from the companion begins. The pulsar gains → angular momentum from the infalling gas and increases its spin rate as more gas falls onto it. → Millisecond pulsars that spin hundreds of times per second are thought to be the result of such a transfer (see, e.g., G. Srinivasan, 2010, New Astronomy Reviews 54, 93, and references therein).

→ recycle; → pulsar.

That part of the electromagnetic spectrum, with a wavelength between 610 and 780 nm, that produces the impression of a variety of colors resembling that of blood.

M.E. red, from O.E. read (cf. Dan. rød, M.Du. root, Ger. rot), from PIE base *reudh- (cf. Av. raoidita- "red, reddish;" Skt. rudhirá- "red, bloody;" L. ruber "red;" Gk. erythros "red").

Sorx "red" (variants Tâleši sər, Kurd. sûr), from Mid.Pers. suxr "red;" O.Pers. θuxra-; Av. suxra- "red, of fire-color;" Ossetic syrx, surx "red;" cf. Skt. śukrá- "clear, pure, bright."

A concentration, on the → horizontal branch, of → red giant stars that roughly have the same intrinsic brightness. These core → helium burning stars are the metal rich equivalents of the better known → horizontal branch stars. Theoretical models predict that their absolute luminosity only weakly depends on their age and chemical composition.

→ red; → clump.

A star on the → horizontal branch which results from the evolution of a → red giant with an initial mass of ~ 1 Msun.

→ red; → clump; → star.

A small, cool, very faint, main sequence star whose surface temperature is under about 3500 K. Red dwarfs generally have masses of less than one-third that of the Sun. In the neighbourhood of the Sun the majority of stars are red dwarfs.

→ red; → dwarf.

A certain star of spectral type K or later that occupies the upper right portion of the → H-R diagram. Red giants are evolved stars that have exhausted their hydrogen fuel in the core. They may have a → luminosity up to 1000 times greater than → main sequence stars of the same → spectral type. Red giants belong to the → luminosity class III or II (bright giants). They are luminous because of their great size, but have a relatively low surface temperature. All normal stars are expected to pass eventually through a red-giant phase as a consequence of stellar evolution. When a main sequence star has converted approximately 10% of its hydrogen to helium, nuclear reactions in the core stop (→ Schönberg-Chandrasekhar limit). The → hydrostatic equilibrium is no longer maintained, and the core contracts while the outer layers expand and cool. This process produces the low surface temperature and large size (from 10 to 100 times that of the Sun) that characterize the red giant. In the core the temperature continues to rise. When it approaches 100,000,000 K helium will begin to fuse into carbon. → helium flash. Prominent bright red giants in the night sky include → Aldebaran and → Arcturus.

→ red; → giant.

The evolutionary path of a star that has exhausted its available hydrogen content in the core, between the → main-sequence turnoff and the → helium flash.

→ red giant; → branch.

Same as → red horizontal branch star.

→ red; → horizontal; → branch; → star.

A star found on the red part of the → horizontal branch. According to theoretical models, these stars result from the evolution of stars with a mass around 0.8 Msun, higher than that giving rise to → BHB stars. Upon helium burning in their cores, the remnant envelope of the red giant collapses.

→ red; → horizontal; → branch; → star.

Unwanted secondary window in a filter band pass, on the red side of the main window.

→ red; leak, from M.E leken, from O.N. leka "to drip, leak;" akin to Du. lek, Ger. lech "leaky," O.E. leccan "to moisten."

Našt "leak, leakage," of unknown origin; sorx, → red.

See → Great Red Spot, on Jupiter.

→ red; → spot.

A supergiant star with spectral type K or M. Red supergiants are the largest stars in the Universe, but not necessarily the most massive. Betelgeuse and Antares are the best known examples of a red supergiant.

→ red; → supergiant.

A member of a class of exploding stars that are more luminous than → novae but not as luminous as → supernovae. Moreover, their outburst → light curves have multiple peaks. One of the most characteristic features of red transients is that after exploding they cool down to → late-type → M star and develop circumstellar material rich in molecules and dust. Some of the members of the red transients in our Galaxy are V838V, OGLE-2002-BLG-360, V4332 Sgr, and V1309 Sco.

→ red; → transient.

Of a spectral line profile, the → line wing with wavelengths longer than that of the emission or absorption peak.

→ red; → wing.