Author: Daniel Verloop

6 March 2017 | Thackeray’s Globules

IC 2944 ESO

Image credit & copyright: ESO | Click image to enlarge or here for full-size

This stunning picture reveals thick clumps of dust silhouetted against the pink glowing gas cloud known as IC 2944. These opaque blobs resemble drops of ink floating in a strawberry cocktail, their whimsical shapes sculpted by powerful radiation coming from the nearby brilliant young stars.

This picture is the sharpest view of IC 2944 ever taken from the ground. The cloud lies about 6500 light-years away in the southern constellation of Centaurus (The Centaur). This part of the sky is home to many other similar nebulae that are scrutinised by astronomers to study the mechanisms of star formation.

Emission nebulae like IC 2944 are composed mostly of hydrogen gas that glows in a distinctive shade of red, due to the intense radiation from the many brilliant newborn stars. Clearly revealed against this bright backdrop are mysterious dark clots of opaque dust, cold clouds known as Bok globules. They are named after the Dutch-American astronomer Bart Bok, who first drew attention to them in the 1940s as possible sites of star formation. This particular set is nicknamed the Thackeray Globules.

Larger Bok globules in quieter locations often collapse to form new stars but the ones in this picture are under fierce bombardment from the ultraviolet radiation from nearby hot young stars. They are both being eroded away and also fragmenting, rather like lumps of butter dropped into a hot frying pan. It is likely that Thackeray’s Globules will be destroyed before they can collapse and form stars.

Bok globules are not easy to study. As they are opaque to visible light it is difficult for astronomers to observe their inner workings, and so other tools are needed to unveil their secrets — observations in the infrared or in the submillimetre parts of the spectrum, for example, where the dust clouds, only a few degrees over absolute zero, appear bright. Such studies of the Thackeray globules have confirmed that there is no current star formation within them.

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