May 31, 2001
Photo No: H2001-16
Hubble Unveils a Galaxy in Living Color
In this view of the center of the magnificent barred spiral galaxy
NGC 1512, NASA Hubble Space Telescope’s broad spectral
vision reveals the galaxy at all wavelengths from ultraviolet to
infrared. The colors (which indicate differences in light intensity)
map where newly born star clusters exist in both "dusty" and
"clean" regions of the galaxy.
This color-composite image was created from seven images taken
with three different Hubble cameras: the Faint Object Camera (FOC),
the Wide Field and Planetary Camera 2 (WFPC2), and the Near
Infrared Camera and Multi-Object Spectrometer (NICMOS).
NGC 1512 is a barred spiral galaxy in the southern constellation of
Horologium. Located 30 million light-years away, relatively "nearby"
as galaxies go, it is bright enough to be seen with amateur telescopes.
The galaxy spans 70,000 light-years, nearly as much as our own
Milky Way galaxy.
The galaxy’s core is unique for its stunning 2,400 light-year-wide
circle of infant star clusters, called a "circumnuclear" starburst
ring. Starbursts are episodes of vigorous formation of new
stars and are found in a variety of galaxy environments.
Taking advantage of Hubble’s sharp vision, as well as its unique
wavelength coverage, a team of Israeli and American astronomers
performed one of the broadest and most detailed studies ever of such
star-forming regions. The results, which will be published in the June
issue of the Astronomical Journal, show that in NGC 1512 newly born
star clusters exist in both dusty and clean environments. The clean
clusters are readily seen in ultraviolet and visible light, appearing
as bright, blue clumps in the image. However, the dusty clusters are
revealed only by the glow of the gas clouds in which they are hidden,
as detected in red and infrared wavelengths by the Hubble cameras.
This glow can be seen as red light permeating the dark, dusty lanes in
"The dust obscuration of clusters appears to be an on-off phenomenon,"
says Dan Maoz, who headed the collaboration. "The clusters are either
completely hidden, enshrouded in their birth clouds, or almost
completely exposed." The scientists believe that stellar winds and
powerful radiation from the bright, newly born stars have cleared
away the original natal dust cloud in a fast and efficient "cleansing"
Aaron Barth, a co-investigator on the team, adds: "It is remarkable how
similar the properties of this starburst are to those of other nearby
starbursts that have been studied in detail with Hubble." This
similarity gives the astronomers the hope that, by understanding the
processes occurring in nearby galaxies, they can better interpret
observations of very distant and faint starburst galaxies. Such
distant galaxies formed the first generations of stars, when the
universe was a fraction of its current age.
Circumstellar star-forming rings are common in the universe. Such
rings within barred spiral galaxies may in fact comprise the most
numerous class of nearby starburst regions. Astronomers generally
believe that the giant bar funnels the gas to the inner ring, where
stars are formed within numerous star clusters. Studies like
this one emphasize the need to observe at many different wavelengths
to get the full picture of the processes taking place.
Members of the group of scientists involved in these observations are:
Dan Maoz (Tel-Aviv University, Israel and Columbia University, USA),
Aaron J. Barth (Harvard-Smithsonian Center for Astrophysics, USA),
Luis C. Ho (The Observatories of the Carnegie Institution of
Washington, USA), Amiel Sternberg (Tel-Aviv University, Israel)
and Alexei V. Filippenko (University of California, Berkeley, USA).
The Space Telescope Science Institute (STScI) 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.