A new class of extremely large telescope is on the drawing board. The European Southern Observatory (ESO) is funding a feasibility study for a ground-based, fully steerable, 100 m optical telescope christened OWL (Over-Whelmingly Large) for its keen night vision.
The project, the brainchild of ESO astronomer Roberto Gilmozzi, uses segmented primary and secondary mirrors and integrated active optics. "OWL owes much of its design characteristics to features of existing telescopes," said ESO engineer Philippe Dierickx.
Indeed, recent breakthroughs in cost-effective optics and mechanical support structures, together with the knowledge gained of active optical control (e.g. at the VLT, Gemini and Subaru), have encouraged astronomers to dream of bigger things.
A 100 m telescope would mean major advances. Imagine measuring the Hubble constant unencumbered by local effects. OWL could measure "standard candles", such as Cepheid variables, as far away as the Virgo cluster; supernovae could be seen up to a redshift of 10 and beyond; and with a large light-collecting area, observations of rapidly varying sources become possible and faint objects, such as planets, can be imaged directly. There is even talk of looking for planetary biospheres.
However, the OWL study is still in an early phase. ESO's activities are currently focused on the completion of the Very Large Telescope and the ALMA project - an array of submillimetre antennae to be installed on Chajnantor in the Chilean Altiplano. "OWL could materialize at the horizon beyond ALMA," said Dierickx. "There is indeed very strong interest in the scientific community to pursue efforts towards such extremely large ground-based telescopes." Current estimates suggest that OWL would cost around a thousand million Euros with a construction time of 11-12 years.