ESO Astronomical Glossary - V


Variable star
A variable star is one whose brightness changes over time-periods ranging from minutes to years. The apparent changes in brightness are caused by different phenomena; some change in size, some eject material, and others are in pairs that periodically obscure and enhance each other (eclipses).

Venus, the second planet from the Sun, is named after the Roman goddess Venus. A terrestrial planet, it is sometimes called Earth's "sister planet", as the two are very similar in size and composition. Although all planets' orbits are elliptical, Venus's orbit is the closest to circular. It is sometimes referred to as the "Morning Star" or the "Evening Star" and is the brightest object in the sky after the Sun and the Moon.

Visible light
Visible light refers to the portion of the electromagnetic spectrum visible to the human eye. It covers the range of wavelengths from 400 to 750 nm.

Visible and Infrared Survey Telescope for Astronomy (VISTA)
VISTA is a 4-metre wide-field survey telescope. It is the world-leading facility for large imaging surveys at infrared wavelengths. It is located at ESO's Paranal site in Chile.

Very Large Telescope (VLT)
The Very Large Telescope (VLT) array is the main telescope at ESO'sParanal site in Chile and the flagship facility of European astronomy. The VLT consists of several interconnected telescopes, of which the main elements are the four reflecting unit telescopes Antu, Kuyen, Melipal and Yepun, with main mirrors of 8.2 m in diameter. The light of the individual telescopes can be combined in the VLT interferometer (VLTI), resulting in superior resolution. The wavelength range covered by the VLT is extremely wide, ranging from deep ultraviolet to mid-infrared.

VLT Interferometer (VLTI)
With the assistance of one or more of the Auxiliary Telescopes, the light of the four VLT Unit Telescopes can be combined to produce a higher resolution to that of a single Unit Telescope.

VLT Survey Telescope (VST)
The VLT Survey Telescope (VST) is a collaboration between the ESO and the Capodimonte Astronomical Observatory (OAC). The VST is a 2.6-metre telescope optimised for high quality astronomical imaging over a wide field of view. The VST is be located at ESO's Paranal Observatory.