ARTWORK BY JON LOMBERG; INSET IMAGE FROM HUBBLE SPACE TELESCOPE
This image shows many features believed to exist
around large galactic black holes like the one in M87.
Mid-infrared observations of M87 have shown that the
torus is missing or extremely faint. Inset: an optical
Hubble Space Telescope image of the core and
prominent M87 jet.

Neighbor galaxy
poses mystery

Mauna Kea scientists can't find
'doughnut' that theory places
on a black hole's menu

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By Rod Thompson
rthompson@starbulletin.com

HILO >> Astronomical theory says black holes are supposed to have a "doughnut" of warm matter spinning around them.

Astronomers have now looked for it and can't find it.

In May, astronomers at the Gemini North Telescope on Mauna Kea looked for the first time at the nearby galaxy M87, known to have a black hole at its center.

Despite instructing the telescope to stare for seven hours at M87 using a new University of Florida image maker, no image of the doughnut, known scientifically as a torus, appeared on the screen, the Gemini observatory announced yesterday.

"Contrary to what most theories predict, our Gemini observations show that the giant elliptical galaxy M87 either lacks a torus around its central black hole, or else this doughnut-shaped ring is extremely faint," said astronomer Eric Perlman at the University of Maryland-Baltimore County, who headed the search.

"With the unparalleled resolution and depth of the Gemini mid-infrared observations, the torus should have been easy to detect," he said.

"This will definitely cause some head-scratching among theorists about how much we really understand regarding the cores of active galaxies like M87," Perlman said.

A black hole traps matter and light that fall into it, but some of both shoot away before they're caught.

Images on the Gemini Web site (www.gemini.edu/gallery/ science/m87) made with X-rays, visible light, radio waves, and now middle-range infrared light, all show a jet of glowing matter shooting out from the black hole.

Immediately surrounding the black hole is a hot, bright "accretion disk" of dense matter ready to fall into it, said Gemini spokesman Peter Michaud.

A torus of cooler, less dense matter should have been circling outside the accretion disk, Michaud said.

Astronomers looked for infrared light from the theorized torus because such light comes from objects, which are warm but not hot.

The Gemini observations looked at light 10 times fainter than any previous ground-based infrared observations.