Magazine article Science News

Probing the Heart of Extragalactic Jets

Magazine article Science News

Probing the Heart of Extragalactic Jets

Article excerpt

Astronomers have come a little closer to finding the origin of the twin jets that shoot out from the brightest objects in the cosmos. Some 10 percent of quasars and active galaxies emit such jets, which extend in opposite directions up to thousands of light-years.

By studying the radio emissions from the jets squirted out by the distant quasar 3C279, researchers have gathered the first compelling evidence that the jets consist mainly of electrons and their antiparticles, positrons. This composition hints at the processes taking place deep within the hearts of active galaxies, where the jets are produced.

Any bright galactic core not powered by starlight is known as an active galactic nucleus. The most luminous of these are called quasars, and they are thought to be fueled by massive black holes. The new observations point to interactions between subatomic particles just outside a black hole as the source of the jets.

John F.C. Wardle and his colleagues at Brandeis University in Waltham, Mass., used the Very Long Baseline Array, a network of 10 radio telescopes, to examine the radio waves emitted by the jets in 3C279. They measured the polarization, the direction in which the electric field of the radio waves oscillates.

In the Oct. 1 Nature, Wardle's team reports finding circularly polarized radiation from the jets, meaning that the angle at which the electric field oscillates is not fixed but rotates around the wave's direction of travel. Earlier observations indicated that most of the radio emission comes from high-speed electrons accelerated by a magnetic field. …

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