The Bizarre New Source GRS1915+105

Previously identified as a source of variable X-ray emission, the source known as GRS1915+105 recently and suddenly showed a rapid increase in its radio flux. Radio astronomers mapping the source have shown that two clumps of high energy particles are being ejected simultaneously from the source at velocities close to the speed of light. The object is probably a collapsed star, a neutron star or black hole formed in a supernova explosion, in orbit with a more normal companion. Material from the companion spirals toward the collapsed remnant, is heated, and thus emits X-rays. Jets of subatomic particles are ejected in opposite directions away from the compact object; high velocity electrons emit synchrotron radiation, detected at radio wavelengths.

By observing the radio emission over several months, Mirabel and Rodriguez (1994) were able to see that the radio emitting plasma blobs were moving. Their apparent motion (change of position with time) implies that they are travelling with velocities greater than the speed of light - an impossibility according to Einstein's theory - and are thus superluminal. However, the apparent motion can also be understood as the result of an illusion caused by the combination of their high velocity (close to but less than the speed of light) and the orientation of the jets along the direction close to the line of sight.

GSR 1915+105 is similar to the better-known bizarre object SS 433.

Comparison of SS433 and GRS1915+105

Source Distance L(X-ray) Velocity of ejecta
GRS1915+105 12.5 kpc 3 x 1038 erg/s 0.92c
SS 433 5.5 kpc 5 x 1035 erg/s 0.26c

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