Stars Love Jets, Cosmic Study Shows

Supermassive black holes at the hearts of galaxies have phenomenal cosmic jets. So do small stellar black holes. Now a baby star ? one that?s still forming ? has been found to rely on the same mechanism to produce its own jets.

Astronomers say they have detected the first evidence of magnetic fields mingling with the charged particles streaming at nearly the speed of light from a young stellar object, a protostar known as IRAS 18162-2048.Illustration of the protostar's cosmic jets]

These cosmic jets spewing from the protostar, which is about 5,500 light-years from Earth, suggest that despite the huge differences in scale, supermassive black holes, stellar black holes and young stars all rely on magnetic fields and shock waves to focus and accelerate charged particles to near light-speed.

"Our discovery gives a strong hint that all three types of jets originate through a common process," said Carlos Carrasco-Gonzalez of the Astrophysical Institute of Andalucia Spanish National Research Council and the National Autonomous University of Mexico.

Carrasco-Gonzalez and his colleagues trained the Very Large Array radio telescope to take a closer look at IRAS 18162-2048 to follow up on earlier evidence that the protostar had a cosmic jet about 17 light-years long. One light-year is the distance light travels in a year, about 6 trillion miles (10 trillion km).

The researchers had to scan the jet for 12 hours to spot faint signs of polarization, or electromagnetic fields oscillating in the same plane. This polarized radiation is emitted when electrons move at near light-speed through a magnetic field.

Researchers had previously detected strong polarization in the relativistic jets from supermassive black holes, as well as from smaller black holes and neutron stars, but they hadn't seen it in the much slower outpourings from young stars.

These diverse objects have a common feature: a massive central body surrounded by a disk of more diffuse material, called an accretion disk.

According to theory, the bending, twisting magnetic fields around such objects sweep up charged particles from the accretion disk and focus them into jets. Fast-moving shock waves then accelerate some of the particles to near light-speed.

For young stars, "it was unclear if it is possible to accelerate some of the electrons up to relativistic velocities," Carrasco-Gonzalez said.

The research is detailed in the Nov. 26 edition of the journal Science.

In a commentary accompanying the new study, Tom Ray of the Dublin Institute for Advanced Studies wrote that even though the shock waves in a young star's jets are relatively slow, they are apparently powerful enough to dramatically accelerate some charged particles.

Ray noted that young stars could therefore serve as test beds for theories of cosmic ray formation, which also are based on the idea of acceleration by shock waves. Some cosmic rays may even be born from young stellar objects, he speculated.

Scientists involved in the study said the findings would have other applications, too.

"In the future, combining several types of observations could give us an overall picture of how magnetic fields affect the young star and all its surroundings," said study co-author Luis Rodriguez, an astronomer with the National Autonomous University of Mexico. "This would be a big advance in understanding the process of star formation."

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