Fr.: étoile à effet Blazhko
A star showing the → Blazhko effect.
blue halo star
setâregân-e âbi-ye hâlé
Fr.: étoiles bleues du halo
Fr.: étoile CNO
setâre-ye O (#)
Fr.: étoile de type O
A luminous, hot, blue star whose spectrum is dominated by the lines of hydrogen, atomic helium, and ionized helium; also known as O-type star. This is the earliest → spectral type and the only → main sequence star in which ionized helium is present. The → effective temperatures of these stars range from about 30,000 K to 50,000 K, their luminosities from 50,000 to 1,000,000 times that of → solar luminosity, and their masses from about 20 to 100 → solar masses. The hottest O-type stars display high ionization emission features such as N III and He II, → Of star. They are divided into subtypes O2, the hottest, to O9.7, the coldest. O-type stars are relatively rare, for each star of 100 solar masses there are 106 stars of solar mass. They are relatively short-lived since they spend only a few million years on the main sequence. The brightest O-type star in the sky visible with naked eye is → Alnitak. For prominent Galactic O stars see → HD 93129.
O, letter of alphabet used in the Harvard spectral classification; → star.
râdio setâré, setâre-ye râdioyi
Fr.: étoile radio
A star which is a source of emission at radio frequencies. Radio stars include pulsars, flare stars, binary star systems in which mass is transferred from one component to the other, and some X-ray stars.
SAO Star Catalog
kâtâlog-e setâre-yi-ye SAO
Fr.: catalogue SAO
A general whole-sky catalog compiled by the Smithsonian Astrophysical Observatory which results from the combination of several earlier catalogs. The compilation gives positions and proper motions for 258,997 stars, of which 8,712 are double and 499 variable, with an average distribution of 6 stars per square degree. The star positions have an average standard deviation of 0''.2 at their original epochs (0''.5 at epoch 1963.5). The equinox is 1950.0 and the system that of the FK4.