Brussels, 08/07/2002 (Agence Europe) - The United Kingdom formally joined the European Southern Observatory (ESO), which brings together Germany, Belgium, Denmark, France, Italy, Netherlands, Portugal, Sweden and Switzerland. It will also participate in the construction of the very large OWL telescope (100 meters in diameter), which will complete the range of giant telescopes (quite a lot smaller) of which ESO already has on the La Silla site in Chile.