These images by NASA's  Hubble  Space  Telescope  show  off  two  dramatically
different face-on views of the spiral galaxy M51, dubbed the Whirlpool Galaxy.

The  image  at  left,  taken  in visible light, highlights the attributes of a
typical spiral galaxy, including graceful,  curving  arms,  pink  star-forming
regions, and brilliant blue strands of star clusters.

In  the  image at right, most of the starlight has been removed, revealing the
Whirlpool's skeletal dust structure, as seen in near-infrared light.  This new
image  is  the sharpest view of the dense dust in M51 The narrow lanes of dust
revealed by Hubble reflect the galaxy's moniker, the Whirlpool Galaxy,  as  if
they were swirling toward the galaxy's core.

To  map  the  galaxy's  dust  structure,  researchers  collected  the galaxy's
starlight by combining images taken in visible and near-infrared  light.   The
visible-light  image captured only some of the light; the rest was obscured by
dust.  The  near-infrared  view,  however,  revealed  more  starlight  because
near-infrared  light  penetrates  dust.    The researchers then subtracted the
total amount of starlight from both images to see the galaxy's dust structure.

The red color in the near-infrared image traces the dust, which is  punctuated
by  hundreds  of  tiny clumps of stars, each about 65 light-years wide.  These
stars have never been seen before.   The  star  clusters  cannot  be  seen  in
visible light because dense dust enshrouds them.  The image reveals details as
small as 35 light-years across.

Astronomers expected  to  see  large  dust  clouds,  ranging  from  about  100
light-years  to  more than 300 light-years wide.  Instead, most of the dust is
tied up in smooth and diffuse dust lanes.  An encounter  with  another  galaxy
may have prevented giant clouds from forming.

Probing  a  galaxy's dust structure serves as an important diagnostic tool for
astronomers, providing invaluable information on how the gas and dust collapse
to  form  stars.   Although Hubble is providing incisive views of the internal
structure of galaxies such as M51, the  planned  James  Webb  Space  Telescope
(JWST) is expected to produce even crisper images.

Researchers  constructed  the  image by combining visible-light exposures from
Jan.  18 to  22,  2005,  with  the  Advanced  Camera  for  Surveys  (ACS)  and
near-infrared-light  pictures  taken  in  December 2005 with the Near Infrared
Camera and Multi-Object Spectrometer (NICMOS)

Object Names: M51, Whirlpool Galaxy  Image Type: Astronomical

Credit for the NICMOS Image: NASA, ESA, M.  Regan and B.  Whitmore (STScI),
and R.  Chandar (University of Toledo)

Credit for the ACS Image: NASA, ESA, S.  Beckwith (STScI), and the Hubble
Heritage Team (STScI/AURA)

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