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A close look at the sky around the star formation region RCW 106
In this huge new image clouds of crimson
gas are illuminated by rare, massive stars that have only recently
ignited and are still buried deep in thick dust clouds. These
scorching-hot, very young stars are only fleeting characters on the
cosmic stage and their origins remain mysterious. The vast nebula where
these giants were born, along with its rich and fascinating
surroundings, are captured here in fine detail by ESO’s VLT Survey
Telescope (VST) at the Paranal Observatory in Chile.
RCW 106 is a sprawling cloud of gas and dust located about 12 000 light-years away in the southern constellation of Norma (The Carpenter’s Square). The region gets its name from being the 106th entry in a catalogue of H II regions in the southern Milky Way . H II regions like RCW 106 are clouds of hydrogen gas that are being ionised by the intense starlight of scorching-hot, young stars, causing them to glow and display weird and wonderful shapes.
RCW 106 itself is the red cloud above centre in this new image,
although much of this huge H II region is hidden by dust and it is much
more extensive than the visible part. Many other unrelated objects are
also visible in this wide-field VST
image. For example, the filaments to the right of the image are the
remnants of an ancient supernova, and the glowing red filaments at the
lower left surround an unusual and very hot star . Patches of dark obscuring dust are also visible across the entire cosmic landscape.
Astronomers have been studying RCW 106 for some time, although it is
not the crimson clouds that draw their attention, but rather the
mysterious origin of the massive and powerful stars buried within.
Although they are very bright, these stars cannot be seen in
visible-light images such as this one as the surrounding dust is too
thick, but they make their presence clear in images of the region at
For less massive stars like the Sun the process that brings them into
existence is quite well understood — as clouds of gas are pulled
together under gravity, density and temperature increase, and nuclear fusion
begins — but for the most massive stars buried in regions like RCW 106
this explanation does not seem to be fully adequate. These stars — known
to astronomers as O-type stars
— may have masses many dozens of times the mass of the Sun and it is
not clear how they manage to gather, and keep together, enough gas to
O-type stars likely form from the densest parts of the nebular clouds
like RCW 106 and they are notoriously difficult to study. Apart from
obscuration by dust, another challenge is the brevity of an O-type
They burn through their nuclear fuel in mere tens of
millions of years, while the lightest stars have lifetimes that span
many tens of billions of years. The difficulty of forming a star of this
mass, and the shortness of their lifetimes, means that they are very
rare — only one in every three million stars in our cosmic neighbourhood
is an O-type star. None of those that do exist are close enough for
detailed investigation and so the formation of these fleeting stellar
giants remains mysterious, although their outsized influence is
unmistakeable in glowing H II regions like this one.
 The catalogue was compiled in 1960 by three astronomers from theMount Stromlo Observatoryin Australia whose surnames were Rodgers, Campbell and Whiteoak, hence the prefixRCW.
 The supernova remnant is SNR G332.4-00.4, also known asRCW 103. It is about 2000 years old. The lower filaments areRCW 104, surrounding theWolf–Rayet starWR 75. Although these objects bear RCW numbers, detailed later investigations revealed that neither of them were HII regions.
ESO is the foremost intergovernmental astronomy organisation in Europe
and the world’s most productive ground-based astronomical observatory by
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Kingdom, along with the host state of Chile. ESO carries out an
ambitious programme focused on the design, construction and operation of
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important scientific discoveries. ESO also plays a leading role in
promoting and organising cooperation in astronomical research. ESO
operates three unique world-class observing sites in Chile: La Silla,
Paranal and Chajnantor. At Paranal, ESO operates the Very Large
Telescope, the world’s most advanced visible-light astronomical
observatory and two survey telescopes. VISTA works in the infrared and
is the world’s largest survey telescope and the VLT Survey Telescope is
the largest telescope designed to exclusively survey the skies in
visible light. ESO is a major partner in ALMA, the largest astronomical
project in existence. And on Cerro Armazones, close to Paranal, ESO is
building the 39-metre European Extremely Large Telescope, the E-ELT,
which will become “the world’s biggest eye on the sky”.