News Release Archive:

News Release 9 of 11

January 3, 2002 12:00 AM (EST)

News Release Number: STScI-2002-01

Thackeray's Globules in IC 2944

A Hubble Heritage Release

January 3, 2002: Strangely glowing dark clouds float serenely in this remarkable and beautiful image taken with the 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. Astronomer A.D. Thackeray first spied the globules in IC 2944 in 1950. Globules like these have been known since Dutch-American astronomer Bart Bok first drew attention to such objects in 1947. But astronomers still know very little about their origin and nature, except that they are generally associated with areas of star formation, called "HII regions" due to the presence of hydrogen gas. IC 2944 is filled with gas and dust that is illuminated and heated by a loose cluster of massive stars. These stars are much hotter and much more massive than our Sun.

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Q & A: Understanding the Discovery

  1. 1. How big is the largest globule?

  2. 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 along its longest dimension. Collectively, the clouds contain enough material to equal over 15 solar masses.

  3. 2. What does Hubble's view reveal to astronomers?

  4. Thanks to the remarkable resolution offered by the Hubble 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 region of glowing hydrogen gas, 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 on a red-hot pan.

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Credits: NASA and The Hubble Heritage Team (STScI/AURA)

Acknowledgment: Bo Reipurth (University of Hawaii)