ESO Astronomical Glossary - O
Omega Centauri is a the largest globular cluster located in the southern constellation Centaurus (The Centaur) at a distance of around 17,000 light years from Earth; it also known as NGC 5139.
See Spectral type.
The term orbit denotes the path an object follows around a more massive object or common center of mass. For astronomical objects orbits are usually elliptical in shape, but cases of circular (close binary stars), parabolic or hyperbolic (comets) orbits are known.
OWL, the 'OverWhelmingly Large Telescope', was a conceptual study for a next-generation optical/infrared telescope, with a primary mirror measuring 100 m in diameter. OWL was ESO's first step towards a European Extremely Large Telescope.