An Etymological Dictionary of Astronomy and Astrophysics
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A → red dwarf in the constellation → Ophiuchus discovered in 1916 by E.E. Barnard, that until 1968 had the largest → proper motion of any star. It moves on the sky 10.3 arcseconds per year, which means that it travels the equivalent of a lunar diameter every 180 years. It is the second nearest star system to the Sun.

In honor of → Barnard; → star.

Same as → 61 Cygni, the first star whose distance was measured, by Friedrich Bessel in 1838.

→ Bessel; → star.

A star near the beginning of the → spectral classification sequence. A star of → spectral type O, B, A, or F0 to F5. Same as → early-type star.

→ early; → spectral; → class; → star.

A star whose mass exceeds 8 solar masses. Same as → massive star. → intermediate-mass star; → low-mass star.

→ high; → mass; → star.

A star whose mass lies in the range about 2 to 8 → solar masses approximately.

→ intermediate; → mass; → star.

A → supernova in → Ophiuchus, first observed on 1604 October 9, and described by Johannes Kepler in his book De stella nova (1606). It reached a maximum → apparent magnitude of -3 in late October. The star remained visible for almost a year. The → light curve is that of a → Type Ia supernova. The → supernova remnant consists of a few filaments and brighter knots at a distance of about 30,000 → light-years. It is the radio source 3C 358. Also known as SN 1604 and Kepler's supernova.

→ Kepler; → star.

The prototype of a small class of stars (A-F types) which have weak metallic lines (indicating that they are depleted in metals heavier than Si, but with solar abundances of C, N, O, and S). Moreover, they have moderately large rotational velocities and small space velocities. Lambda Boo stars may be pre-main-sequence objects, or they may be main sequence stars that formed from gas whose metal atoms had been absorbed by interstellar dust.

Named after the prototype, the star → Lambda (λ) of constellation → Bootes; → star.

A star whose mass is around that of the Sun. See also: → intermediate-mass star; → high-mass star; → star formation.

→ low; → mass; → star.

A → binary system consisting of two → massive stars, which are → supergiants of → spectral types O7.5 and O6. The two components are so close together that they orbit each other with a period of 14.4 days only. The Plaskett's star is a → double-line binary. The estimated masses of the components are 43 (Plaskett A) and 51 (Plaskett B) → solar masses. The lower mass component is optically brighter than the other star. Also known as HR 2422 and HD 47129 (See, e.g., Bagnuolo et al. 1992, ApJ 385, 708).

Named after the Canadian astronomer John S. Plaskett (1865-1941), who made a detailed spectroscopic study of this star in 1922.

A blue star, named HD 101065 or V816 Cen, with an extremely peculiar chemical composition and spectral features. Although the star has a surface temperature very close to that of stars with solar chemical composition, it displays some abundance anomalies typical of much hotter → Ap stars. The spectrum is dominated by a group of lines of → lanthanides, while in the spectra of normal stars with similar temperature the absorption lines of neutral elements from the iron group are predominant. The lanthanides may have abundances 10³-10⁴ times solar. The spectrum of Przybylski's star also shows the presence of radioactive → rare earth elements, such as → promethium and → technetium. Moreover, there are numerous strong absorption lines which defy identification. In some spectrum regions unidentified lines are more numerous than known lines. It is also a → roAp star (see, e.g., Gopka et al. 2008, Kinematics and Physics of Celestial Bodies Vol. 24, No. 2, 89).

Named after its discoverer, Antoni Przybylski (1961, Nature 189, 739).

A type of massive, → blue supergiant, → variable star, also known as a → Hubble-Sandage variable or a → Luminous Blue Variable (LBV). S Doradus stars are the most luminous stars in the Galaxy and are easily identified in other nearby galaxies. They are named after the prototype, S Doradus, in the → Large Magellanic Cloud.

→ Dorado; → star.

A → red giant of → spectral type S whose spectrum is dominated by → molecular bands arising from → zirconium → oxide (ZrO). S stars also have strong → cyanogen bands and contain spectral lines of → lithium and → technetium. Almost all S stars are → long-period variables.

S, letter of alphabet; → star.

A star that is less luminous than a main-sequence star of the same spectral type.

→ sub-; → luminous; → star.

A → supernova of Type Ia in the constellation → Cassiopeia, which Tycho Brahe observed in November 1572. At its peak it was as bright as Venus and was visible in the daytime, reaching a magnitude of about -4. It is now visible as a → supernova remnant about 20 light-years across at a distance of about 7,500 light-years. It is associated with faint emission in the optical and X-rays, but is a strong radio source. Other designations: SN 1572, 3C 10, B Cas, 2U 0022+63.

Named after the Danish astronomer Tycho Brahe (1546-1601), who described the event; → star.

A star with a typical mass of one-hundredth of the mass of the Sun (→ solar mass) and a luminosity of about one-millionth that of the Sun (→ solar luminosity). Same as → brown dwarf.

→ very; → low; → mass; → star.

A member of a class of → pulsating stars with a period of 1 to 35 days located in the → instability strip of the → H-R diagram. Also known as type II Cepheid variables, W Virginis stars are typically 1.5 mag fainter than classical Type I Cepheids and have a mass less than that of the Sun. They also exhibit a period-luminosity relation which is distinct, but works in a similar way to the relation for Type I Cepheids. Hence W Virginis stars can also be used to measure Galactic and extragalactic distances.

W, alphabetical letter; → variable star designation; → Virgo; → star.