Astronomy from the moon in the next decades: from exoplanets to cosmology in visible light and beyond.

We look at what astronomy from the Moon might be like over the next few decades. The Moon offers the possibility of installing large telescopes or interferometers with instruments larger than those on orbiting telescopes. We first present examples of ambitious science cases, in particular ideas that cannot be implemented from Earth. After a general review of observational approaches, from photometry to high contrast and high angular resolution imaging, we propose as a first step a 1-metre-class precursor and explore what science can be done with it. We add a proposal to use the Earth-Moon system to test the quantum physics theory. This article is part of a discussion meeting issue 'Astronomy from the Moon: the next decades (part 2)'.

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'.

Hypertelescope with multiplexed fields of view.

Hypertelescope interferometers having many highly diluted sub-apertures are capable of directly imaging, within a narrow field of view, celestial objects at a high resolution thanks to pupil densification. This Letter verifies with OpticStudio modeling the possibility of simultaneously imaging multiple such fields. A strategy of multi-field sampling uses a microlens array to generate multiplexed field channels, where independent active corrections of the tip-tilt and piston are applied for compensating for the off-axis aberrations. Adopting this strategy, we have designed a model of a multi-field hypertelescope with OpticStudio. The reported design expands the observing performance of hypertelescopes for directly imaging multiple sources with very high angular resolution.