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In 1977, Stephenson and Sanduleak published a catalogue of optical
emission line objects showing a very strong 
line.
Object number 433 of that catalogue is also a strong radio source and an X-ray
emitter and is also known as 4C04.66 (Gower et al., 1967) and A 1909+04
(Seward et al., 1980) and 4U 1908+05 (Forman et al., 1978).
SS 433 is also a variable star V 1343 Aql (Kholopov et al., 1981).
Although this object is known under several names, the one that is mostly
used is SS433. The position is 
.
SS433 is an eclipsing binary star. The orbital period is almost 13 days (the
binary separation is of the order of 1 AU (
cm)). The
magnitude outside eclipses is 
, although this value can change
with the precession period. Most people think that the system consists of
an early type star and an accretion disk around a compact object. The
accretion disk gives a symmetry plane, which is generally agreed to be the
most plausible environment for producing (near) relativistic beams in a
stellar object.
What makes this object special is the fact
that antiparallel beams emanate from the source at near-relativistic speed.
The reason why SS433 was so popular at the beginning of the 1980's was based
on the hope that by studying the jets of this object one could learn a lot
about jet physics in general and apply this knowledge to extra-galactic jets
in particular.