A microquasar, the smaller version of a quasar, is a compact region surrounding a black hole with a mass several times that of our sun, and its companion star. The matter being pulled from the companion star forms an accretion disk around the black hole. This accretion disk may become so hot, due to friction, that it begins to emit X-rays. The disk also projects narrow streams or "jets" of subatomic particles at near-light speed, generating a strong radio wave emission.
In some cases, blobs or "knots" of brighter plasma within the jets appear to be traveling faster than the speed of light, an optical illusion called superluminal motion which is caused by sublight speed particles being projected at a small angle relative to the observer.
The 1996 Bruno Rossi Prize of the American Astronomical Society was awarded to Felix Mirabel, and Luis Rodriguez, for their discovery of the superluminal motion of radio knots in GRS 1915+105, as well as the discovery of double-sided radio jets from galactic sources 1E1740.7-2942 and GRS 1758-258.
Due to the smaller size of microquasars, many of the effects are scaled differently in relation to normal quasars. In quasars, the mean temperature of the accretion disk is several thousand degrees, while in a microquasar the mean temperature is several million degrees. The average size of the accretion disk of a quasar is 1,000,000,000 square kilometres (390,000,000 sq mi), whereas in microquasars the average size is only 1,000 square kilometres (390 sq mi). Quasars can project jets up to several million light years, whereas microquasars can project them only a few light years; however, the "knots" within the jets of a microquasars can exhibit a proper motion (angular motion across the sky) on the order of a thousand times faster than that of knots within a quasar jet because observed microquasars (being within the Milky Way galaxy) are at typical distances on the order of kiloparsecs, rather than hundreds of megaparsecs to several gigaparsecs.
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- "HEAD AAS Rossi Prize Winners". www.head.aas.org. Retrieved 27 August 2017.
- Mirabel, Felix; Rodriguez, Luis F. (1994). "A superluminal source in the Galaxy". Nature. 371 (6492): 46–48. Bibcode:1994Natur.371...46M. doi:10.1038/371046a0.
- Mirabel, Felix (1994). "Multiwavelength approach to gamma-ray sources in the Galactic center region". Astrophys. J. Suppl. Ser. 92: 369–373. Bibcode:1994ApJS...92..369M. doi:10.1086/191980.
- "Microquasars as sources of high energy phenomena -I.F. Mirabel". ned.ipac.caltech.edu. Retrieved 19 January 2017.