The Vela Molecular Ridge is a vast star-forming complex in the plane of our Galaxy, the Milky Way. Observing this region at far-infrared wavelengths, ESA's Herschel Space Observatory has obtained an extraordinarily detailed image of the most massive component of this molecular complex, known as Vela-C.


This image reveals previously unseen detail in the cold mixture of gas and dust that pervades the region. Cosmic dust is a minor but crucial component of the interstellar medium and, due to its low temperature, it shines brightly at the far-infrared wavelengths that Herschel is designed to observe. By detecting emission from cosmic dust, astronomers can unravel the distribution of the raw material out of which stars form.


A number of white flecks dot the clouds and, in particular, the prominent ridge-like filaments in Vela-C. These flecks are in fact pre-stellar cores – compact clumps of matter that might eventually give rise to star formation – and proto-stellar cores, whose density is high enough for star formation to have already begun, eventually resulting in fully-fledged stars. As a result of Herschel's unparalleled resolution and sensitivity at these wavelengths, astronomers are able to carry out detailed studies of the properties, such as their mass and temperature, of the different cores across the nests and filaments. From the Herschel image, it appears that the majority of pre- and proto-stellar cores with large masses are found along the two densest filaments, suggesting that these sites are the most likely, in the cloud, to host the formation of massive stars.

Studies done with Herschel data seem to indicate that the ridge-like filaments in star-forming regions such as Vela-C formed from converging flows of matter in the interstellar medium. The high densities in these thick, elongated structures induce massive clumps of matter to collapse under their own gravity, giving rise to high-mass stars. The nest-like structures, on the other hand, appear to be dominated by turbulence rather than by gravity and are likely to form mainly low- and intermediate-mass stars.


ESA/PACS& SPIRE Consortium, Tracey Hill, Frédérique Motte, Laboratoire AIM Paris-Saclay, CEA/IRFU - CNRS/INSU - Uni. Paris Diderot, HOBYS Key Programme


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