US astronomer who has worked particularly
on the identification of galaxies.
He published Atlas of Peculiar Galaxies 1965.
He also carried out the first photometric work on the Magellanic Clouds
- the nearest extragalactic system.
Arp was born in New York and educated at Harvard and the California
Institute of Technology.
In 1953 he began research at the observatory on Mount Palomar, and after
working at a number of other institutions returned there in 1969.
During the 1980s he put forward some unorthodox views on the red shifts
In the ensuing controversy he left the Palomar Observatory and went
to the Max Planck Institute for Astrophysics, near Munich, in Germany.
During his research on globular clusters, globular-cluster variable
stars, novae, Cepheid variables, extragalactic nebulae, and so on, Arp
has attempted to relate the listings of galaxies to radio sources; the
optical identification of these sources can now be done fairly accurately.
He is working with other astronomers on the question whether the red
shifts in the spectrum of quasars are due to the general expansion of