Wolf 424

Until 1915 the bright star Alpha Centauri was steadfastly regarded by astronomers as the sun's nearest stellar neighbor.

Its distance from the sun is 4.3 light years --about 25 trillion miles. In 1915 Dr. Robert T. A. Innes of Johannesburg discovered, by parallax observations,* that a faint star near Alpha Centauri was only 4.16 light-years away. For 23 years, up to last week, that star, appropriately called Proxima Centauri, held rank as the No. 1 solar neighbor. Last week, from the University of Chicago's Yerkes Observatory in Wisconsin, it was announced that another faint star, Wolf 424/- appears to be only 3.7 light-years distant. This is so close that a train traveling a thousand miles a day would get there in 60 million years.

Professor Gerard Pieter Kuiper found that Wolf 424 has an unusual "very late M-type" spectrum which indicates that the star is 50,000 times less luminous than the sun. Its apparent magnitude is 11.8, which is about six magnitudes be low the limit of naked-eye visibility. Comparison of the apparent with the intrinsic brightness yielded the distance.

Director Otto Struve of Yerkes would not say for sure that Wolf 424 is the sun's nearest known neighbor. It may be a double star, in which case the combined light of the two components would make it appear closer than it actually is. Parallax measurements requiring a year or more will be necessary to settle the contest between Proxima Centauri and Wolf 424.

*Parallax is the apparent motion of a star caused by the earth's revolution around the sun. The nearer the star, the larger the apparent motion.

/-Named for the late German Astronomer Max Wolf of Heidelberg.

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