A stars

A stars

Stars of spectral type A. They are blue-white or white and have a surface temperature (T eff) of about 7500 to 9900 kelvin for main-sequence stars, and up to 12 000 K for supergiants. Balmer absorption lines of hydrogen dominate the spectrum, reaching maximum strength for A0 to A3 stars; lines of ionized and neutral metals slowly strengthen with the H and K lines of ionized calcium appearing in later subdivisions. A few A stars (Am and Ap stars) have anomalously high abundances of metals and rare earth elements. Color indices for A0 stars are zero. Vega, Sirius, Deneb, and Altair are A stars.
References in classic literature ?
"O sister," said the little one, as she gazed at the sky, "I wish that the Dew Elves, as they wander lightly by, Would bring me a star; for they never grow dim, And the Father does not need them to burn round him.
If we assume, as science normally does, the continuity of physical processes, we are forced to conclude that, at the place where the plate is, and at all places between it and a star which it photographs, SOMETHING is happening which is specially connected with that star.
If the observer had then specially directed his attention to one of the more humble and less brilliant of these stellar bodies, a star of the fourth class, that which is arrogantly called the Sun, all the phenomena to which the formation of the Universe is to be ascribed would have been successively fulfilled before his eyes.