European Southern Observatory - ESO's Observing Sites in Chile - Paranal - Very Large Telescope

Very Large Telescope

The main facility at Paranal is the VLT, which consists of four near-identical 8.2-metre Unit Telescopes (UTs), each hosting two or three instruments. These large telescopes can also work together, in groups of two or three, to form a giant 'interferometer', the ESO Very Large Telescope Interferometer or VLTI, allowing astronomers to see details up to 25 times finer than those seen with the individual telescopes. The light beams are combined in the VLTI using a complex system of mirrors located in underground tunnels where the light paths must be kept equal to distances less than 1/1000 mm over a hundred metres. With this kind of precision, the VLTI can achieve an angular resolution of milliarcseconds, equivalent to distinguishing the two headlights of a car at the distance of the Moon.

The first of the UTs had its first light in May 1998 and was offered to the astronomical community on 1 April 1999. The other telescopes followed suit in 1999 and 2000, thus making the VLT fully operational. Four 1.8-metre Auxiliary Telescopes (ATs) have been added to the VLTI to make it available when the UTs are being used for other projects. These ATs were installed between 2004 and 2007. Results from the VLT have led to the publication of an average of more than one peer-reviewed scientific paper per day. For instance, only in 2007, almost 500 refereed scientific papers were published based on VLT data. The VLT's scientific discoveries include imaging an extrasolar planet for the first time, tracking individual stars moving around the supermassive black hole at the centre of the Milky Way, and observing the afterglow of the furthest known gamma-ray burst.