CORE OF SPIRAL GALAXY M51                    STSCI PRC 92-17
Wide Field/Planetary Camera

This image of the core of the nearby spiral galaxy M51, taken with the
Wide Field Planetary Camera shows a striking, dark "x" silhouetted
across the galaxy's nucleus.  The "x" is due to absorption by dust and
marks the exact position of a suspected black hole which may have a
mass equivalent to one million stars like the Sun.  The darkest bar may
be an edge-on dust ring which is 100 light-years in diameter.  The
edge-on torus not only hides the black hole and accretion disk from
being viewed directly from Earth, but also determines the axis of a jet
of high speed plasma and confines radiation from the accretion disk to
a pair of oppositely directed cones of light, which ionize gas caught
in their beam.  The second bar of the "x" could be a second disk seen
obliquely, or possibly rotating gas and dust in M51 interacting with
the jets and ionization cones.