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TOPIC: VIRUS-W spectrograph

Blobrana

L

Posts: 131433

Date: Jan 25 09:14 2011

First Light for VIRUS-W spectrograph	Permalink

VIRUS-W beobachtet zum ersten Mal eine Spiralgalaxie The new observing instrument VIRUS-W, built by the Max Planck Institute for Extraterrestrial Physics and the University Observatory Munich, saw "first light" on 10th November at the Harlan J. Smith Telescope of the McDonald observatory in Texas. Its first images of a spiral galaxy about 30 million light-years away where an impressive confirmation of the capabilities of the instrument, which can determine the motion of stars in near-by galaxies to a precision of a few kilometres per second. As imaging field spectrograph, VIRUS-W can simultaneously produce 267 individual spectra - one for each of its glass fibres. By dispersing the light into its constituent colours, astronomers thus are able to study properties such as the velocity distribution of the stars in a galaxy. For this they use the so called Doppler shift, which means that the light from stars moving towards or away from us is shifted to blue or red wavelengths, respectively. This effect can also be observed on Earth, when a fast vehicle, such as a racing car, is driving past: the sound of the approaching car is higher, while for the departing car it is lower. VIRUS-W's unique feature is the combination of a large field of view (about 1x2 arcminutes) with a relatively high spectral resolution. With the large field of view astronomers can study near-by galaxies in just one or few pointings, while the high spectral resolution permits a very accurate determination of the velocity dispersion in these objects. In this way the astronomers obtain the large-scale kinematic structure of near-by spiral galaxies, which gives important insight into their formation history. Read more __________________

Blobrana

L

Posts: 131433

Date: Jun 8 16:58 2010

VIRUS-W spectrograph	Permalink

View of the night sky with more than 250 eyes End of May, the VIRUS-W spectrograph of the Max Planck Institute for Extraterrestrial Physics and the University Observatory Munich was completed and is now ready for installation at the McDonald observatory in Texas. Its field of view, spectral coverage and resolution makes the instrument ideally suited to study star and gas motions in nearby spiral galaxies. Images of astronomical objects are not only beautiful and impressive but also an important source of information for astronomers. In addition to imaging cameras, scientists also use instruments called spectrographs, which disperse light into its constituent colours. The spectra obtained in this fashion help to determine for example the chemical composition of stars and gas or their velocities. The VIRUS-W spectrograph was specifically designed to observe nearby spiral galaxies. Its relatively large field of view combined with a high spectral resolution makes it ideally suited for this purpose. Operated in the high resolution mode, it will allow scientists to study the bulk motion of stars in spiral galaxies down to velocity dispersions ( ) of only about 20 km/s. The second, medium resolution mode was developed for studying the chemical composition of galaxies. The field of view of the spectrograph will be about 150x75 arcseconds, which means that the kinematically very interesting central regions of spiral galaxies can be studied in just one or two exposures. Depending on its apparent brightness and size on the sky, a galaxy can then be observed in just a few hours. Read more __________________

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