US astronomer whose
work has included studies of high-velocity stars, red giants (using
narrow- and broadband photometry), and subluminous stars.
Born in Orfordville, Wisconsin, Eggen graduated from Wisconsin University.
He has spent much of his working life in senior appointments all round
the world; he was director of Mount Stromlo and Siding Spring observatories,
Australia, 1966-77, when he moved to the Observatory Interamericano
de Cerro Tololo, Chile.
During the mid-1970s, Eggen completed a study - based on ultraviolet
photometry and every available apparent motion - of all red giants brighter
than apparent magnitude 5. As a result he was able to classify these
stars, categorizing them as very young discs, young discs, and old discs.
A few remained unclassifiable (haloes).
He also systematically investigated the efficiency of the method of
stellar parallax using visual binaries originally suggested by William
Herschel in 1781, and reviewed the original correspondence of English
astronomers John Flamsteed and Edmond Halley.