Chandra observes cosmic traffic pile-up in energetic Quasar jet
Using the unrivaled high resolution of NASA’s Chandra X-ray
Observatory, astronomers have seen important new details in the powerful jet
shooting from the quasar 3C273. This research, coupled with optical and
radio data, may reveal how these very high velocity jets are driven from the
supermassive black holes that scientists believe lurk in the center of
quasars.
“For the first time, Chandra has given us an X-ray view into the
area between 3C273’s core and the beginning of the jet,” says Herman
Marshall of the Massachusetts Institute of Technology (M.I.T.) in Cambridge,
Mass., and lead author on the paper submitted to Astrophysical Journal
Letters. “Instead of being void of X-ray emission, Chandra has enabled us to
detect a faint, but definite, stream of energy.”
The high-powered jets driven from quasars, often at velocities very
close to the speed of light, have long been perplexing for scientists.
Instead of seeing a smooth stream of material driven from the core of the
quasar, most optical, radio, and earlier X-ray observations have revealed
inconsistent, “lumpy” clouds of gas.
This newly discovered continuous X-ray flow in 3C273 from the core
to the jet may reveal insight on the physical processes that power these
jets. Scientists would like to learn why matter is violently ejected from
the quasar’s core, then appears to suddenly slow down.
“If there is a slower car in front on a highway, a faster one from
behind will eventually catch up and maybe cause a wreck,” says Marshall. “If
the jet flow velocity changes, then gas shocks may result, which are akin to
car collisions. These gigantic clouds of high-energy electrons, now seen in
X-rays with Chandra, may indeed be the result of some sort of cosmic traffic
pile-up.”
The X-ray power produced in one of these pile-ups is tremendous. For
example, the X-ray output of the first knot in the jet is greater than that
of most Seyfert galaxies, which are thought to be powered by supermassive
black holes. The abundance of X-ray emission suggests that large amounts of
energy may also be produced in gamma rays, a question that researchers are
unable to resolve with current telescopes.
The energy emitted from the jet in 3C273 probably comes from gas
that falls toward a supermassive black hole at the center of the quasar, but
is redirected by strong electromagnetic fields into a collimated jet. While
the black hole itself is not observed directly, scientists can discern
properties of the black hole by studying the jet. The formation of the jet
from the matter that falls into the black hole is a process that remains
poorly understood.
The quasar 3C273 is no stranger to making astronomical news.
Discovered in the 1960s, 3C273 was one of the first objects to be recognized
a “quasi-stellar” object, due to its incredible optical and radio
brightness, but perplexing properties. Only after careful consideration did
astronomers determine that 3C273 and others of its ilk were not nearby
stars, but instead incredibly powerful objects billions of light years away.
The Chandra observation of 3C273 was made with both the Low Energy
Transmission Grating (LETG) and the High Energy Transmission Grating (HETG),
in conjunction with the High Resolution Camera (HRC) and the Advanced CCD
Imaging Spectrometer (ACIS).
n addition to Dr. Marshall, the team of researchers includes J.J.
Drake, A. Fruscione, J. Grimes, D. Harris, M. Juda, R. Kraft, S.S. Murray,
D. Pease, A. Siemiginowska, S. Vrtilek, and B.J. Wargelin of the
Harvard-Smithsonian Center for Astrophysics, P.M. Ogle of M.I.T., and S.
Mathur of Ohio State University.
The HRC was built for NASA by the Smithsonian Astrophysical
Observatory. The HETG and ACIS instruments were built for NASA by M.I.T. and
Pennsylvania State University. The LETG was built by the Space Research
Organization of the Netherlands and the Max Plank Institute.
NASA’s Marshall Space Flight Center in Huntsville, Ala., manages
the Chandra program. TRW, Inc. of Redondo Beach, Calif., is the prime
contractor for the new spacecraft. The Smithsonian’s Chandra X-ray Center
controls science and flight operations from Cambridge, Mass.
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