| 单词 | barnard's star |
| 释义 | Barnard's starBar·nard's starB5083050 (bär′nərdz)Barnard's starBarnard's starBarnard's star,star with the largest observed proper motionproper motion,in astronomy, apparent movement of a star on the celestial sphere, usually measured as seconds of arc per year; it is due both to the actual relative motions of the sun and the star through space. Proper motion reflects only transverse motion, i.e. ..... Click the link for more information. (rate of motion across the sky with respect to other stars); located in the constellation Ophiuchus. The star's large proper motion, 10.28" per year (or half the moon's apparent diameter in a century), is due in part to the fact that it is the second-nearest star, being at a distance of 5.98 light-years. Barnard's star was discovered in 1916 by E. E. Barnard, an observer known also for his discoveries of 16 comets. It is a faint red dwarf star, apparent magnitudemagnitude, in astronomy, measure of the brightness of a star or other celestial object. The stars cataloged by Ptolemy (2d cent. A.D.), all visible with the unaided eye, were ranked on a brightness scale such that the brightest stars were of 1st magnitude and the dimmest stars ..... Click the link for more information. 9.5, of spectral classspectral class, in astronomy, a classification of the stars by their spectrum and luminosity. In 1885, E. C. Pickering began the first extensive attempt to classify the stars spectroscopically. ..... Click the link for more information. M5, lying near the bottom of the main sequence in the Hertzsprung-Russell diagramHertzsprung-Russell diagram [for Ejnar Hertzsprung and H. N. Russell], graph showing the luminosity of a star as a function of its surface temperature. The luminosity, or absolute magnitude, increases upwards on the vertical axis; the temperature (or some temperature-dependent ..... Click the link for more information. . Slight oscillations in its motion indicate that it has at least one unseen companion. Barnard's starA red dwarf star in the constellation Ophiuchus that was discovered in 1916 by E.E. Barnard. The fourth-nearest star to the Sun, after the Alpha Centauri system, it has the largest known proper motion (10″.3 per year) and thus moves a distance equivalent to the Moon's diameter in 180 years. Observations of the star's position over many years show slight oscillating variations in right ascension and declination. It is thought that this wobbling motion is due to the presence of one or more planets orbiting the star. mv : 9.53; Mv : 13.21; spectral type: M4 V; distance: 1.83 pc.Barnard's star[′bär·nərdz ¦stär] |
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