The brightest lights in the universe often come from the
blackest pits of deep space.
Black holes, so named because even light cannot escape their
gravitational grasp, can only be sensed through their tug on other matter.
While black holes themselves are invisible, the regions around them are reigned
by powerful magnetic and gravitational forces that create some of the most
luminous radiation ever seen.
Super-bright anomalies like cosmic
rays, plasma jets and gamma-ray bursts pour forth to fly across the
universe, and researchers are just beginning to untangle the mysteries of how they
arise.
Infinitely dense
Black holes are extremely
dense masses jammed into single points of space. At their centers, all the
matter is crushed to infinite density inside a space of zero volume, called a
singularity. There, the pull of gravity is thought to be infinitely strong,
warping space-time to be infinitely
curved.
Yet, for all the bizarre happenings inside black holes, if
you are sufficiently far enough away from them, they act like any other matter.
That means that if the sun were replaced with a black hole of the same mass,
all the planets would continue to orbit around it just as usual, scientists
have said, though Earth would not be habitable due to lack of sunlight.
Black holes are thought to form during the explosive deaths
of very massive stars. When a star exhausts all its fuel, it implodes under the
crushing force of gravity into a denser and denser ball, eventually reducing
down to a black hole. Meanwhile, the outside layers of the star are expelled in
a powerful blast called a supernova.
Rays, bursts and jets
Scientists think some of the energy released by the
explosion and formation of a black hole goes toward accelerating particles to
great speeds, creating marvels called cosmic rays that fly through the universe
at almost the speed of light. We detect some of these particles on Earth, where
they still pack such a punch they can knock out electronics systems.
Another consequence of black holes and supernovas are short
flashes of high-energy gamma-ray light called gamma-ray
bursts. They originate in distant galaxies and are the brightest things
ever seen in the universe. The bursts likely arise when a very massive,
rapidly-rotating star collapses into a black hole during a supernova explosion,
and releases a short, intense beam of gamma-ray radiation.
And black holes also seem to be to blame for the jets of hot
charged gas seen spewing from the hearts of distant galaxies. These galaxies, called
blazars, likely have supermassive black holes in their centers that are
warping space-time in extreme ways. As dust and gas gets dragged toward a black
hole, some of it is spit back out and accelerated by twisted magnetic fields
around the black hole to shoot out in luminous jets that can be seen across the
universe.
"We studied a battery mechanism to extract the energy of
a spinning black hole, and it provides a compelling way to power jets in high-energy
gammaray sources," said Govind Menon, a professor of physics at Alabama's
Troy University.
Menon recently wrote the book "High Energy Radiation
from Black Holes: Gamma Rays, Cosmic Rays, and Neutrinos," (2009,
Princeton University Press) with astrophysicist Charles Dermer of the Space
Science Division of the Naval Research Laboratory. The two scientists spoke
about the topic Nov. 4 at the 2009 Fermi Symposium in Washington, D.C.
The researchers said even more secrets of black holes are
likely to be discovered soon thanks to new experiments like the Fermi Gamma-ray
Space Telescope, the South Pole IceCube Neutrino Experiment, ground-based TeV
(1000 GeV) gamma-ray detectors, and the Pierre Auger Cosmic Ray Observatory in
Argentina.
"This is a decade of incredible scientific discovery in
high-energy astronomy and astroparticle physics," Dermer said.
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