Whirlpool Galaxy (M51) Cross

NASA's Hubble Space Telescope has provided astronomers with what may be their first direct view of an immense ring of dust which fuels a massive black hole at the heart of the spiral galaxy M51, located 20 million light-years away. Surprisingly, they found that the ring is standing almost perpendicular to the relatively flat spiral galaxy, like a top spinning on its side with respect to the floor. Even more surprising is the discovery of a secondary ring or dust lane which is contrary to all expectations.

These observations are being reported by Dr. Holland Ford (Johns Hopkins University and Space Telescope Science Institute), and his Faint Object Spectrograph Team co-investigators at the 180th meeting of the American Astronomical Society in Columbus, Ohio.

"Pictures of M51 taken with the [Hubble] Planetary Camera show a striking, dark "X" silhouetted across the nucleus. The "X" is due to absorption by dust and marks the exact position of the nuclear black hole," says Ford. "If these ideas are correct, M51 provides the first direct view of a torus [ring] which both fuels a massive black hole and hides the hole from direct view from anyone outside the ionization cone [narrow cone of light emitted from the near-vicinity of the black hole].

Commonly called the Whirlpool Galaxy, M51 is one of the nearest and brightest galaxies, having an angular diameter 1/3rd the width of the Full Moon. The galaxy is spectacular because it is tilted nearly face-on to Earth, allowing for an unobstructed view of its the bright core. M51 is especially noteworthy because its well-defined spiral arms are unusually bright, and the end of one of the spiral arms projects across a small, dusty and distorted satellite galaxy.

Previous observations made with both radio and optical telescopes have revealed energetic activity in the core of the galaxy. Hot ionized gas in the center of M51 is moving at speeds of up to two million miles per hour. Ground-based observations also show a pair of radio and corresponding optical "bubbles" which form a double-lobed structure across the nucleus.

The new HST images now offer the best glimpse yet of the near-vicinity of the "powerhouse" driving these fireworks. The pictures reveal an hour-glass structure formed by two bright beacons of light that are so energetic they cause interstellar gas caught in their beams to glow through ionization. This double cone "searchlight" is bisected by the widest bar of the dark "X". "This suggests that the dark band in the 'X', which is perpendicular to the ionization cone, may be a rotating torus of cold gas and dust seen edge-on," says Ford.


News Release 651 of 701
June 8, 1992 09:30 AM (EDT)
News Release Number: STScI-1992-17

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