Astronomy:
The black hole GX 339-4, near the center of our galaxy, has a
mass at least six times greater than our Sun and is orbited by
a companion star that feeds it. Most of the material from the
star is pulled into the black hole, but some of it is blasted
outward at nearly the speed of light.Poshak Gandhi from the
Japan Aerospace Exploration Agency and colleagues have used
data from NASA's Wide-Field Infrared Survey Explorer (WISE) to
zoom in on the area around the base of the jet. They found that
the jet's base has an average radius of about 24 000 km and
that it can fluctuate by at least a factor of 10. The jet's
activity also undergoes significant and dramatic fluctuations
on time scales ranging from 11 seconds to a few hours. Their
observations suggest GX 339-4's magnetic field is 30 000
times more powerful than that of Earth. The field provides the
black hole with the necessary force to accelerate and channel
the flow of matter from its companion star into a jet.
