No. 40: Jul-Aug 1985
Radio-telescope measurements of the compact radio source, churning away in the center of our Galaxy, reveal that it is only 20 AU in diameter at radio wavelengths of l.35 centimeters. This is roughly the size of the solar system inside Saturn's orbit. This tiny radio source is so energetic that there seems no escaping the conclusion that it is a blackhole. No other astronomical object is capable of generating so much energy in so small a volume. Since other galaxies also seem to harbor small, but very powerful radio sources in their centers, astronomers wouldn't be too surprised if all galaxies had black-hole cores. Quasars, in fact, might be galaxies with spectacularly active centers.
Would these unseeable black holes be the notorious "missing mass" in the universe? Not likely. The mass of the purported black hole in our Galaxy is only about several million solar masses-- not even close to what is needed.
(Maddox, John; "Black Hole at the Galactic Centre," Nature, 315:93, 1985.)
Comment. Actually, it would be rather amusing if the problem of the missing mass, which we cannot see, were solved by black holes, which we cannot see either!
Reference. Black holes and other cosmological entities are discussed in our Catalog: Stars, Galaxies, Cosmos. to order the book, visit: here.