HUBBLE EVEALS THE HEART OF THE WHIRLPOOL GALAXY
New images from
NASA's Hubble Space Telescope are helping researchers
view in unprecedented detail the spiral arms and
dust clouds of a nearby galaxy, which are the birth
sites of massive and luminous stars.
The Whirlpool galaxy,
M51, has been one of the most photogenic galaxies
in amateur and professional astronomy. Easily photographed
and viewed by smaller telescopes, this celestial
beauty is studied extensively in a range of wavelengths
by large ground- and space-based observatories.
This Hubble composite image shows visible starlight
as well as light from the emission of glowing hydrogen,
which is associated with the most luminous young
stars in the spiral arms.
M51, also known
as NGC 5194, is having a close encounter with a
nearby companion galaxy, NGC 5195, just off the
upper edge of this image. The companion's gravitational
pull is triggering star formation in the main galaxy,
as seen in brilliant detail by numerous, luminous
clusters of young and energetic stars. The bright
clusters are highlighted in red by their associated
emission from glowing hydrogen gas.
This Wide Field
Planetary Camera 2 image enables a research group,
led by Nick Scoville (Caltech), to clearly define
the structure of both the cold dust clouds and the
hot hydrogen and link individual clusters to their
parent dust clouds. Team members include M. Polletta
(U. Geneva); S. Ewald and S. Stolovy (Caltech);
R. Thompson and M. Rieke (U. of Arizona).
is also seen for the first time in the dust clouds.
Along the spiral arms, dust "spurs" are seen branching
out almost perpendicular to the main spiral arms.
The regularity and large number of these features
suggests to astronomers that previous models of
"two-arm" spiral galaxies may need to be revisited.
The new images also reveal a dust disk in the nucleus,
which may provide fuel for a nuclear black hole.
The team is also
studying this galaxy at near-infrared wavelengths
with the NICMOS instrument onboard Hubble. At these
wavelengths, the dusty clouds are more transparent
and the true distribution of stars is more easily
seen. In addition, regions of star formation that
are obscured in the optical images are newly revealed
in the near-infrared images.
This image was
composed by the Hubble Heritage Team from Hubble
archival data of M51 and is superimposed onto ground-based
data taken by Travis Rector (NOAO) at the 0.9-meter
telescope at the National Science Foundation's Kitt
Peak National Observatory (NOAO/AURA) in Tucson,
and The Hubble Heritage Team (STScI/AURA)
Acknowledgment: N. Scoville (Caltech) and T. Rector