SS 433 - DWARF QUASAR IN OUR GALAXY?
SS 433
RA = 19h 10m 20.57s
DEC = +4° 55' 54.31" Distance = 4.9 kpc (16,000 ly)
The strangeness of SS 433 was first noted in 1978. In that year 2 papers were published, in 1979 28 papers appeared, 73 papers in 1980 and 122 papers in 1981. 779 papers are listed on the Astronomical Data System search engine through 1997. First catalogued as Stephenson-Sanduleak 433, some of the strange qualities of SS 433 include,
1) emission lines showing simultaneous redshift and blueshift of 30,000 km/sec and 50,000 km/sec respectively.
2) a powerful X-ray emitting binary star system
3) twin jets of material ejecting high speed electrons to velocities of 0.26c (26% the speed of light)
4) 164 day precession period of the jets (spinning like a top)
5) SS 433 appears to be embedded in an old supernova remnant W50,
6) gamma ray observations indicate that nuclear fusion reactions are occurring in the jets.
Figure 1 shows the radio emitting material moving outward from the core at 26% the speed of light. This shows the changing lobe pattern over 2 months. First, knots A and B begin to be ejected outward. Then new knots C and D are formed and continue to be ejected outward. This outward pressure may be responsible for the elongated shape of the supernova remnant W50.
Figure 1. Radio contour maps showing the expansion and creation of “jet” moving at 0.26c over a 10 week time interval.
The current explanation of what is being seen here is a luminous binary star in which one component, a blue supergiant, transfers material to an accretion disk around its compact companion, perhaps a neutron star or black hole. Matter rains down so fast that the disk becomes “overloaded” and two jets of gas are ejected in opposite directions at right angles to the disk. Because the accretion disk is precessing, or wobbling like a top, with a period of 164 days, the jets also slew around in the same interval.
Ralph Spencer of Jodrell Bank, England studied the fine line radio structure of SS 433. Shortly after a radio outburst of the central source, he observed knots of emission moving away from the unresolved core, expanding and fading on a time scale of 35 days, see Figure 1. The expanding knots combined with velocities from visible spectra, imply a distance of 4.9 kpc in good agreement with other methods. The energy levels required for such ejections is on the order of 25,000 times the Sun. But Spencer notes that the energy output is probably much higher, since we cannot expect 100% efficiency in the conversion of kinetic energy (of the beams) into radio emission.
The supernova remnant W50, appears to be stretched in an east-west direction, possible due to the outward spiral motion by the jets. See Figure 2.
Figure 2. SS 433 inside an overlaid image of the supernova remnant W50. Note the left-right stretching of W50 by the jets of SS 433.
Is SS 433 a tiny model of a extra-galactic model of cosmic jets apparently seen in galaxies? The major problem seen by astronomers is that the fast moving electrons being ejected through the beams lose energy fast as they spiral around the magnetic field lines. In a quasar, electrons stop emitting synchrotron radiation long before they traversed the long jet involved. Thus in a quasar, there must be some re-accelerating mechanism as the electrons move outward.
The object SS 433, is such a bizarre object that a book was written about it, “The Quest for SS 433”, by David H. Clark, 1985 Viking Penguin, Inc.
REFERENCES
Brinkmann, W., Aschenbach, B., Kawai, N., 1996, ROSAT Observations of the W50/SS 433 System, Astronomy and Astrophysics, 312, p. 306
Collins, G.W.II, Newsom, G.H., 1986, A Dynamical Model for SS433, Astrophysical Journal, 308, p. 144.
Margon, B., 1984, Observations of SS433, Annual Review of Astronomy and Astrophysics, 22, p. 507-536.
Spencer, R.E., 1984, Flux Density and Structure Variations in SS 433, Monthly Notices of the Royal Astronomical Society, 209, p. 869-879.