The Bat Nebula - IC 2948
CCD image with false color
and
Hubble Image with Thackeray's Globules
 

Above:  cut-out from my image rotated to orientation of Hubble Image below.

This CCD image on the top was taken with an SBIG ST8E camera with a H-alpha filter.  It is the combination of six, five-minute exposures.  The images were processed using Mira, CCDSharp, MaxIm DL and Photoshop.  My friend Ray Gralak provided critical help and advice with the processing.  This nebula is part of a larger complex with the other major section labeled IC 2944.  The image was taken from Coonabarabran, NSW, Australia.  It was shot through an AP 5" f/6.
 

The middle image is a blow-up of  a few of the Thackeray's Globules shown in the Hubble Image.

The bottom image is explained by this text from the Hubble Heritage web site:

          Strangely glowing dark clouds float serenely in this remarkable and beautiful image taken with
          NASA's Hubble Space Telescope. These dense, opaque dust clouds - known as "globules" - are
          silhouetted against nearby bright stars in the busy star-forming region, IC 2944. These globules
          were first found in IC 2944 by astronomer A.D. Thackeray in 1950.

          Although globules like these have been known since Dutch-American astronomer Bart Bok first
          drew attention to such objects in 1947, little is still known about their origin and nature, except that
          they are generally associated with large hydrogen-emitting star-formation regions, called "HII
          regions" due to their glowing light of hydrogen gas.

          The largest of the globules in this image is actually two separate clouds that gently overlap along our
          line of sight. Each cloud is nearly 1.4 light-years (50 arcseconds) along its longest dimension, and
          collectively, they contain enough material to equal over 15 solar masses. IC 2944, the surrounding
          HII region, is filled with gas and dust that is illuminated and heated by a loose cluster of O-type
          stars. These stars are much hotter and much more massive than our Sun. IC 2944 is relatively close
          by, located only 5900 light-years (1800 parsecs) away in the constellation Centaurus.

          Thanks to the remarkable resolution offered by the Hubble Space Telescope, astronomers can for
          the first time study the intricate structure of these globules. The globules appear to be heavily
          fractured, as if major forces were tearing them apart. When radio astronomers observed the faint
          hiss of molecules within the globules, they realized that the globules are actually in constant, churning
          motion, moving supersonically among each other. This may be caused by the powerful ultraviolet
          radiation from the luminous, massive stars, which also heat up the gas in the HII region, causing it to
          expand and stream against the globules, leading to their destruction. Despite their serene
          appearance, the globules may actually be likened to clumps of butter put onto a red-hot pan.

          It is likely that the globules are dense clumps of gas and dust that existed before the massive O-stars
          were born. But once these luminous stars began to irradiate and destroy their surroundings, the
          clumps became visible when their less dense surroundings were eroded away, thus exposing them to
          the full brunt of the ultraviolet radiation and the expanding HII region. The new images catch a
          glimpse of the process of destruction. Had the appearance of the luminous O-stars been a bit
          delayed, it is likely that the clumps would actually have collapsed to form several more low-mass
          stars like the Sun. Instead they are now being toasted and torn apart.

          The hydrogen-emission image that clearly shows the outline of the dark globules was taken in
          February 1999 with Hubble's Wide Field Planetary Camera 2 (WFPC2) by Bo Reipurth
          (University of Hawaii) and collaborators. Additional broadband images that helped to establish the
          true color of the stars in the field were taken by the Hubble Heritage Team in February 2001. The
          composite result is a four-color image of the red, green, blue and H-alpha filters.

          Image Credit: NASA and The Hubble Heritage Team (STScI/AURA)
          Acknowledgment: Bo Reipurth (University of Hawaii)

 


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