Imaging ever closer to the event horizon

Image of a bright disk surrounding a dark sphere.

Enlarge / Artist’s
conception of a blob of hot matter orbiting close to surface of a
black hole. At this distance, its orbit is influenced by the black
hole’s spin. (credit: NASA/CXC/M.
Weiss
)

While black holes themselves swallow any light beyond their
event horizon, the area outside the event horizon tends to emit
lots of light. That’s because the material falling in toward the
black hole is extremely energetic as it sheds angular momentum and
crashes in to other material in orbit around the black hole. So,
while we can’t image a black hole directly, we can infer some
things about its properties using light from the environment it
creates.

This week saw the publication of two papers that edge in to the
area close to the event horizon, imaging events in an area that
includes some of the closest stable orbits to the black hole. And,
in doing so, one of them finds that a supermassive black hole is
spinning so fast that a location on its surface would move at
roughly half the speed of light.

Echoes of a corona

Both of these papers take advantage of periodic outbursts that
happen when the black hole starts to feed on new material. That
material heads into the hole via a flat structure centered on the
black hole called an accretion disk. Its arrival heats the disk up,
causes the black hole to brighten, and causes changes in the local
environment. The questions that these two papers focus on is what
these changes can tell us about the black hole and the environment
nearby.

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Source: FS – All – Science – News
Imaging ever closer to the event horizon