A STAR THAT BREATHES
Beta Cephei, the mysterious Milky Way star which expands and contractsas though it were breathing, at last has a biography.
A summary of known facts concerning the star, interpreted in the lightof recent observations at the Lick Observatory at the University ofCalifornia was completed recently by H. S. Mendenhall, graduate student.
Mendenhall's interpretations were said to lend weight to the theory thatBeta Cephei is contracting and expanding once in every four and one-halfhours. This is such a terrific rate of speed from a terrestrial point ofview that it appears to be moving toward and away from the earth at avelocity reaching a maximum of about nine and one-half miles per second.
Beta Cephei is a variable star in the Constellation Cepheus. It is bestvisible in the northern sky during July or August. Its distance from theearth is estimated roughly at 2,000,000,000,000,000 miles, andMendenhall estimates its diameter at almost 2,000,000 miles, more thantwice that of the sun.
In addition to the apparent velocity caused by contraction and expansionof its surface five times a day, Beta Cephei seems to have anothermotion. This was said by Mendenhall to be a rotation around some otherstar in a period of 20 years. Velocity of this rotation is somethingover three miles a second.
Variable stars are of particular interest to astronomers because thelight from them pulsates regularly, flaring and dying as though fuelwere replenished at regular intervals. The rate of this pulsation hasbeen found to be a measure to the candle power of the star. Its distancethen can be determined by contrasting its actual candle power with theapparent magnitude as seen from the earth.
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