Artist concept of our Milky Way galaxy

A team of physicists from the Jet Propulsion Laboratory reported today that they have identified an object in the Milky Way galaxy that is emitting high-energy gamma radiation 50,000 times as great as the total power output of the Sun.

Dr. Allan S. Jacobson told the American Physical Society's annual meeting in Baltimore today that radiation from the object, called SS 433, appears to come from the isotope magnesium 24. Observations at lower energies by other scientists have indicated SS 433's behavior is unlike any other object in our galaxy. "The new observations make unique object even more bizarre," Jacobson said.

Jacobson says data gathered by the High-Energy Astronomy Observatory (HEAO-3) shows that the radiations occur at two different energies -- one at 1.5 million electron volts and second at 1.2 million electron volts. Jacobson and his colleagues believe the data are consistent with single energy of 1.369 million electron volts.

Two jets of material appear to stream from SS 433, the scientists say, one toward Earth and the other away. Because of their different velocities relative to Earth, radiation from the receding jet shifts toward the lower energies and the radiation from the approaching jet shifts toward higher energies. In this picture, the higher-energy radiation is from the jet coming toward us, the lower-energy radiation from the jet moving away.

According to Dr. Richard Lamb, who led the analysis, the precise energies associated with each radiation shift by few percent over several weeks as the jets change their orientation in space relative to Earth.

The physicists say the material appears to be moving at 26 percent of the speed of light (Light moves at 186,200 miles second), and -- if it is indeed magnesium 24 -- it must have been heavily nuclear processed. (Nuclear processing takes place in the interior of stars, and synthesizes elements from the original hydrogen and helium.)

The source of the radiation, they say, could be neutron star buried within SS 433. neutron star is star with about the same mass as the Sun that has collapsed to diameter of only few miles. Another, more exotic, possibility is that SS 433 contains black hole.

The scientists believe the neutron star or black hole in SS 433, which is 15,000 light years from Earth, must have formed within the last 1,000 to 10,000 years, and that the jets pouring from it are punching holes in the interstellar medium around it.

SS 433, while in the Milky Way galaxy, appears to be undergoing processes on relatively small scale that occur on larger scale in quasars and active galaxies, scientists say.

Dr. Lamb is at JPL on leave from Iowa State University. Other members of the team, in addition to Lamb and Jacobson, are James Ling, Guenter Riegler, William Wheaton and William Mahoney, all of JPL.

The HEAO-3 satellite was launched by NASA in 1979 to observe the sky in high-energy-radiation ranges.

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