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A spectacular demonstration of the power of the new VLT Survey Telescope (VST), and its camera, OmegaCAM, has arrived from the European Southern Observatory. The proof is this extremely wide field image of the triplet of galaxies in Leo, made up of M65 (top right), M66 (lower right) and NGC 3628 (left). These are weakly interacting spiral galaxies, located at a distance of about 35 million light years from Earth.
The result of a collaboration between ESO and INAF (Istituto Nazionale di Astrofisica, Italy), the VST, with a diameter of 2.6 metres, is the largest telescope in the world dedicated to photographic surveys of the sky, and is the only instrument with a field of view large enough to obtain an image like that above, in a single frame. Other large telescopes can, at most, photograph these galaxies one at a time.
The enormous field of view of the VST is accompanied by a gigantic digital camera, OmegaCAM, the sensor of which has 268 megapixels. This can detect both very nearby objects as well as the distant galaxies and quasars of the early Universe, with exceptional resolution.
A very large field of view and high resolution are fundamental to the task for which the VST was built, that is to continuously survey the halo of our galaxy (the low density stellar halo that envelops the spiral arms in the disk) in search of microlensing events. These are a sudden brightening of a background star due to the passage of an intervening brown dwarf, giant planet of collapsed star.
The study of these otherwise invisible objects is fundamental to the understanding of the nature of dark matter, and in this field, like that of dark energy, that acts on much larger scales, the role of the VST will be decisive.
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