Black hole silhoue t te
Scientists attempt to
image a shadow and
its tumultuous ring
By Charles Petit
Black holes are among the most bashful yet flamboyant charac- ters on the cosmic stage. They consume matter so voraciously
that the violence can ignite brilliant
beacons called quasars, bright enough
to outshine entire galaxies. Yet because
they prevent light from escaping or even
bouncing off, black holes themselves are
also the ultimate unseeables.
By studying light around a black hole,
scientists may determine how fast it
spins (examples from models shown).
vatories that usually operate independently. The new array’s magnifying power
will exceed that of any telescope or array
made so far. Two targets await: the monster black hole believed to reside at the
center of the Milky Way, home galaxy to
sun and Earth, and an even more massive
black hole at the core of a distant galaxy.
“If we get the first image of the silhouette of a black hole, it will be on the cover
of textbooks the next year,” says Avi
Loeb, a member of the team pushing the
idea and head of the Institute for Theory
and Computation at the Harvard-Smithsonian Center for Astrophysics in
Cambridge, Mass.
A close collaborator of Loeb’s, Avery
Broderick, has been working on black
holes and extreme gravitational fields
since he began his studies at New York’s
Stony Brook University, and then at
Caltech. Now at the Canadian Institute
for Theoretical Astrophysics in Toronto,
he sees a rare chance to add observa-
tions to a field that has been almost all
theory. “It is essentially critical to show
that black holes really exist,” Broderick
says. “We don’t know that they do. It has
become so common to talk about them.
Their existence is the simplest assump-
tion to make. We couldn’t test it, so we
internalized it as fact.”
Black hole shadows would look like
bull’s-eyes in space. Surrounding each
circle of darkness would be a thin ring of
brilliant radiation — a spray of photons
briefly caught in orbit around the black
hole itself. Flaring farther out, distorted
and warped by the light-bending nature
of spacetime near a black hole, would be
a billowing, billion-plus degree plasma
heated by internal friction as its parti-
cles orbit and jostle at high speeds.
