Beta Cephei, the mysterious Milky Way star which expands and contracts
as though it were breathing, at last has a biography.
A summary of known facts concerning the star, interpreted in the light
of recent observations at the Lick Observatory at the University of
California was completed recently by H. S. Mendenhall, graduate student.
Mendenhall's interpretations were said to lend weight to the theory that
Beta Cephei is contracting and expanding once in every four and one-half
hours. This is such a terrific rate of speed from a terrestrial point of
view that it appears to be moving toward and away from the earth at a
velocity reaching a maximum of about nine and one-half miles per second.
Beta Cephei is a variable star in the Constellation Cepheus. It is best
visible in the northern sky during July or August. Its distance from the
earth is estimated roughly at 2,000,000,000,000,000 miles, and
Mendenhall estimates its diameter at almost 2,000,000 miles, more than
twice that of the sun.
In addition to the apparent velocity caused by contraction and expansion
of its surface five times a day, Beta Cephei seems to have another
motion. This was said by Mendenhall to be a rotation around some other
star in a period of 20 years. Velocity of this rotation is something
over three miles a second.
Variable stars are of particular interest to astronomers because the
light from them pulsates regularly, flaring and dying as though fuel
were replenished at regular intervals. The rate of this pulsation has
been found to be a measure to the candle power of the star. Its distance
then can be determined by contrasting its actual candle power with the
apparent magnitude as seen from the earth.