![]() This suggests a source not larger than a light-millisecond or 300 km, so it is very compact. This X-ray source exhibits rapid variations, with time scales on the order of a millisecond. This is of course not a proof of a black hole - but it convinces most astronomers.įurther evidence that strengthens the case for the unseen object being a black hole is the emission of X-rays from its location, an indication of temperatures in the millions of Kelvins. The calculated mass of the dark object is 8-10 solar masses much too massive to be a neutron star which has a limit of about 3 solar masses - hence black hole. Using the period plus spectral measurements of the visible companion's orbital speed leads to a calculated system mass of about 35 solar masses. Doppler studies of the blue supergiant indicate a revolution period of 5.6 days about the dark object. So something massive but non-luminous is there (neutron star or black hole).ģ. A blue supergiant star, about 25 times the mass of the sun, was found which is apparently orbiting about the x-ray source. X-ray sources are candidates for black holes because matter streaming into black holes will be ionized and greatly accelerated, producing x-rays.Ģ. An x-ray source was discovered in the constellation Cygnus in 1972 (Cygnus X-1). ![]() Themass of the companion is calculated tobe 8-10 solarmasses, much toolarge to be a neutron star.ġ. The B-type blue supergiant (HDE226868) is projected to have a mass of about 25 solar masses. Some astronomers think the binary system V404 Cygni is the strongest candidate yet.ĭoppler studies of this blue supergiant in Cygnusindicate a period of5.6 days in orbit around an unseen companion. Another excellent candidate in an object which was discovered in one of the Magellanic Clouds. The indirect evidence for the black hole Cygnus X-1 is a good example of the search for black holes. The strongest evidence for black holes comes from binary systems in which a visible star can be shown to be orbiting a massive but unseen companion. Since black holes by their very definition cannot be directly observed, proving their existence is difficult. Once they collapsed past a certain radius, the "event horizon", then even light could not escape: black hole. Such neutron stars would collapse toward zero spatial extent - toward a "singularity". But this neutron force is the last stand, and our best calculations indicate that this repulsion which prevents collapse cannot withstand the gravity force of masses greater than 2 to 3 solar masses. Black Holes in Binary Systems Black Holes in Binary SystemsĪfter collapse to the neutron star stage, stars with masses less than 2-3 solar masses should remain neutron stars, gradually radiating away their energy, because there is no known mechanism for further combination, and forces between neutrons prevent further collapse.
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