Lunar optical interferometry and hypertelescope for direct imaging at high resolution.

Following earlier proposals for optical stellar interferometer concepts in space and on the Moon, the improved 'hypertelescope' version capable of direct high-resolution imaging with a high limiting magnitude became tested on Earth, proposed for space, and is now also proposed for the Moon. Many small mirrors can be dilutely arrayed in a lunar impact crater spanning 10-25 km. And a larger version, modified for a flat lunar site and spanning up to several hundred kilometres can be built later if needed for a higher resolution and limiting magnitude. Even larger versions, at the scale of many thousand kilometres, also appear feasible in space at some stage, in the form of a controlled flotilla of mirrors. Among the varied science targets considered with the imaging resolution expected, reaching 100 nano-arcseconds on the Moon, are: (a) the early detection and resolved imaging of Near Earth Objects, and their monitoring for eventual collision avoidance by orbital deflection; (b) multi-pixel imaging of exoplanets as part of the search for exolife by mapping local seasonal spectral variations; (c) the physics of neutron stars and black holes at the galactic centre and in other Active Galactic Nuclei; and (d) distant galaxies of cosmological interest. This article is part of a discussion meeting issue 'Astronomy from the Moon: the next decades'.