From the Physics Today Archive – March 2015

By: Amanda Nelson, Associate Archivist

“Gravitational collapse” by Hong-Yee Chiu, May 1964

Cover of May 1964 issue of Physics Today.

Quasars or quasi-stellar radio sources are the most energetic and distant members of a class of objects called active galactic nuclei (AGN). The first quasars were discovered in the late 1950s and were noted as radio sources with no corresponding visible object. In 1963, Allan Sandage and Thomas A. Matthews published about the definite identification of the radio source 3C 48 with an optical object.

Recently Universe Today’s website published an article discussing how to try to see quasars with a backyard telescope and some additional resources for quasar hunting. In Universe Today’s article, it mentions the first appearance of the term “quasar” was in a Physics Today article from May 1964. This article will be free content for six months and the abstract is available below.

To learn more about quasars and some of the original people who discovered them. See our online oral history interview transcripts and search “quasar” or read one of our four interviews with Allan Sandage from 1974 May 16, 1977 February 8, 1978 May 22 and 23, and 1989 January 11.

Abstract: With the exception of a few supernova remnants which are in our galaxy, most cosmic radio sources are “radio galaxies”. Although flare stars do emit radio waves occasionally, no ordinary stars with strong, steady radio emission have been found. The typical optical power of stars is from 1030 ergs/sec (white dwarfs) to 1038 ergs/sec (super giants). For comparison, the optical power of the sun is 4×1033 ergs/sec. The typical radio power of supernova remnants is around 1036 ergs/sec. For a giant galaxy (containing approximately 1011−1012 stars with a total mass of around 1011⊙, where ⊙ = solar mass = 2×1033g), the optical power is around 1044 ergs/sec. Radio emission from normal galaxies is generally weaker, the power ranging from 1037−1039 ergs/sec. For certain peculiar galaxies, the so‐called “radio galaxies,” the radio emission rate ranges from 1041−1044.5 ergs/sec.

Quasi‐stellar radio sources, a subject of intense interest since their discovery in 1960, were the central theme of the International Symposium on Gravitational Collapse and Other Topics in Relativistic Astrophysics, held in Dallas, December 16 to 18, 1963. During the meeting, at the request of L. V. Berkner, it was renamed the John F. Kennedy Memorial Symposium. The author of this review of the discussions is a physicist at NASA's Goddard Institute for Space Studies and an adjunct assistant professor at Columbia University.