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Image of the Day: Haunting Bok Globules in a Spectacular Stellar Nursery

 

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This new view of a spectacular stellar nursery reveals thick clumps of dust silhouetted against the pink glowing gas cloud known to astronomers as IC 2944. The image celebrates an important anniversary for the Very Large Telescope— the world's most advanced optical instrument operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. Among the observations carried out using the VLT are the first direct image of an exoplanet, the tracking of individual stars moving around the supermassive black hole at the center of the Milky Way, and observations of the afterglow of the furthest known gamma-ray burst.

It is fifteen years since the first light on the first of its four Unit Telescopes, on 25 May 1998. Since then the four original giant telescopes have been joined by the four small Auxiliary Telescopes that form part of the VLT Interferometer (VLTI). The VLT is one of the most powerful and productive ground-based astronomical facilities in existence. In 2012 more than 600 refereed scientific papers based on data from the VLT and VLTI were published.

Interstellar clouds of dust and gas are the nurseries where new stars are born and grow. The new picture shows one of them, IC 2944, which appears as the softly glowing pink background. The nebula is associated with the bright star cluster IC 2948 and both of these names are also sometimes associated with the whole region. Many of the bright cluster stars appear in this picture.

This image is the sharpest view of the object 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, discovered from South Africa by the English astronomer A. David Thackeray in 1950.

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.

This region of sky has also been imaged in the past by the NASA/ESA Hubble Space Telescope (opo0201a). This new view from the FORS instrument on ESO’s Very Large Telescope at the Paranal Observatory in northern Chile covers a wider patch of sky than Hubble and shows a broader landscape of star formation.


The Daily Galaxy via ESO

Comments

So, why don't new born stars clump together due to gravity
and mutual attraction? What forces them apart?

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