Microquasars are astronomical objects that can be regarded as miniature versions of quasars due to the observed properties.
In contrast to a quasar, in which it is an active galactic nucleus with a supermassive black hole is in a microquasar is a binary star system with a stellar black hole or a neutron star with only a few solar masses. This collapsed core of a neutron star or a black hole, is this a normal star orbits in a very tight orbit. Here, the compressed object accretes matter from the companion star and pushes them out.
In general it can be assumed that it is a microquasar with an accreting object lighter than 3 solar masses is a neutron star - quasar with a neutron star as a motor. However, the neutron star can evolve through the acquisition of mass to a black hole.
The microquasar shows as well as a quasar strong and variable radio emission, which can often be observed as radio jets and an accretion disk, which is highly luminous in the optical and X-ray range. The accretion disk is formed by a material transfer to the compact object.
The most widespread theory assumes that one of the two stars of a binary pair at the end of its life cycle, after the collapse to a neutron star or a black hole begins to suck through his extreme gravitational field of matter from its companion star and thus to form a Akkreditionsscheibe. Under certain circumstances, the flow of matter here is so great that the compact component ejects the material in the form of a collimated beam of material to approximately the speed of light.
Furthermore, one might speculate that a microquasar can be caused by a traveling in a star system black hole.
Observations and occurrences
The X-ray satellite GARNET discovered in 1994 40,000 light years from GRS 1915 105. The microquasar consisting of a star with about one solar mass orbiting a black hole with a ~ 14 times the solar mass, and is thus one of the most massive stellar black holes.
Another microquasar LS 5036 is much closer with a distance of 9,100 light years. The two radio jets are about 2.6 billion kilometers long. This corresponds to about 2.6 light hours and would be projected on our solar system, starting range from the sun, about to between Saturn and Uranus.
In the observation of LS 5036 was found, however, that this radiates quite weak in X-rays. This might suggest that future searches could classify many such X-ray faint objects as quasars. If this is true, it could be that a substantial, if not principal, part of the high-energy particles and radiation in the Milky Way are due to microquasars.
The next known microquasar and its black hole is V4641 Sagittarii, removed in only about 1,500 light years from Earth.
Examples in the Milky Way
Other well-known microquasars in the Milky Way are: Cyg X-1, Cyg X-3, Cir X-1, XTE J1748 -288, LS 5039, GRO J1655 -40, XTE J1550 -564 and Sco X -1.
Ultra Luminous X-ray sources in other galaxies
Due to the anisotropic orientation of the jets and the relativistic effects leads to a pooling of radiation in the direction of the jets. It is therefore presumed that the ultra-bright X-ray sources are microquasars in other galaxies whose jets are oriented towards Earth. The term ultra -luminous X-ray sources is because the luminosity exceeds the Eddington limit of black holes with stellar mass.
Microquasars as gamma-ray binaries
Gamma-ray binaries emit electromagnetic radiation with energies above 200 keV. The gamma radiation in the case of microquasars is the result of inverse Compton scattering of ultraviolet radiation with charged particles at relativistic jet of microquasar. In this case, there is temporal correlation between the radio radiation and gamma radiation. The gamma radiation always occurs with a time delay of a few days and the inverse Compton scattering is therefore likely to occur in the outer regions of the jet. The energy of the gamma radiation can reach values of 1036 erg and is thus of the order of the emitted X-rays.
Importance for astronomy
Of particular interest in microquasars are the relativistic radio jets. The jets form near the black hole, so that the time scale of changes are made proportional to the mass of the black hole. An ordinary quasar has up to several million solar masses and microquasars sometimes only a few solar masses.
Due to the very different mass scales between quasars and microquasars the temporal variability of such jets can be studied on the basis of microquasars as it were in motion. Thus, changes in the jets of a microquasar within a day often correspond to the change in the jet of a quasar in centuries. Through this, compared to quasars, relatively rapid radiation of observed particles and formation of jets, it is possible microquasars and to observe its changes scientifically in much shorter periods.