 Galactic
Silhouettes
This new image from NASA's Hubble Space Telescope
and its Wide Field Planetary Camera 2 (WFPC2) shows the unique galaxy
pair called NGC 3314. Through an extraordinary chance alignment,
a face-on spiral galaxy lies precisely in front of another larger
spiral. This line-up provides us with the rare chance to visualize
dark material within the front galaxy, seen only because it is silhouetted
against the object behind it.
Dust lying in the spiral arms of the foreground galaxy
stands out where it absorbs light from the more distant galaxy.
This silhouetting shows us where the interstellar dust clouds are
located, and how much light they absorb. The outer spiral arms of
the front galaxy appear to change from bright to dark, as they are
projected first against deep space, and then against the bright
background of the other galaxy.
NGC 3314 lies about 140 million light-years from Earth,
in the direction of the southern hemisphere constellation Hydra.
The bright blue stars forming a pinwheel shape near the center of
the front galaxy have formed recently from interstellar gas and
dust.
In many galaxies, interstellar dust lies only in the
same regions as recently formed blue stars. However, in the foreground
galaxy, NGC 3314a, there are numerous additional dark dust lanes
that are not associated with any bright young stars.
A small, red patch near the center of the image is
the bright nucleus of the background galaxy, NGC 3314b. It is reddened
for the same reason the setting sun looks red. When light passes
through a volume containing small particles (molecules in the Earth's
atmosphere or interstellar dust particles in galaxies), its color
becomes redder.
The Hubble Heritage color image of NGC 3314 was constructed
from archival images taken with WFPC2 in April 1999 by Drs. William
Keel and Ray White III (University of Alabama) in blue and infrared
light, combined with new images obtained by the Heritage team in
March 2000 using blue, green and red filters.
Credit: NASA
and The Hubble Heritage Team (STScI/AURA)
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STScI-PRC00-14
The
Space Telescope Science Institute
is operated by the Association
of Universities for Research in Astronomy, Inc. (AURA), for NASA,
under contract with the Goddard
Space Flight Center, Greenbelt, MD. The Hubble Space Telescope is a project
of international cooperation between NASA and the
European Space Agency (ESA).
