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  • 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 ring.

    “The dust obscuration of clusters appears to be an on-off phenomenon,”
    says 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.

    Credit: NASA, ESA, and D. Maoz (Tel-Aviv University and Columbia University)