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| Easy introduction to RAVE |
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The radial velocity is the speed with which a star moves towards us or away from us. Any motion in space consists of two parts: the velocity on the celestial sphere which is perpendicular to the line of sight, and the radial velocity which is parallel to the line of sight. The radial velocity is being measured by RAVE for more than 1,000,000 stars. |
| Astrometric space missions like HIPPARCOS (finished) and GAIA (planned) provide the exact positions of a star on the celestial sphere, the distance from the Earth and the motion on the celestial sphere. The missing component - the radial velocity - is measured by RAVE. |
| The motion projected onto the celestial sphere is called "proper motion" of a star. While the measurement of this needs precise positions for several years, the radial velocity requires a very precise spectrum of the star. |
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| The principles |
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RAVE uses the Doppler effect on spectral lines for the determination of the velocity along the line of sight. |
| Spectral range investigated: 8400-8750 Â |
| Doppler shift of Ca triplet lines, also favored by the astrometric GAIA mission |
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| The survey |
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Pilot study (2003-2005): 100,000 targeted stars on southern hemisphere using existing hardware and unscheduled time on the UK Schmidt at Siding Spring |
| The 6dF instrument with 150 fibres is used to obtain 150 stellar spectra in one field of view |
| Main study (2006-2010): over 1 million stars, magnitude limited, southern hemisphere survey |
| More details... | |
