A cryogenic liquid-mirror telescope on the moon to study the early universe

TL;DR

This paper explores the feasibility and scientific potential of deploying large cryogenic liquid-mirror telescopes on the moon to observe the early universe, demonstrating key technologies and identifying optimal locations.

Contribution

It introduces the concept of lunar liquid-mirror telescopes, demonstrates critical technologies like ionic liquid coatings and superconducting bearings, and assesses optimal lunar locations for such observatories.

Findings

Lunar liquid mirrors can operate at cryogenic temperatures with suitable ionic liquids.

Locations near the lunar poles are ideal for deep sky observations.

Key technologies for lunar liquid-mirror telescopes have been successfully demonstrated.

Abstract

We have studied the feasibility and scientific potential of zenith observing liquid mirror telescopes having 20 to 100 m diameters located on the moon. They would carry out deep infrared surveys to study the distant universe and follow up discoveries made with the 6 m James Webb Space Telescope (JWST), with more detailed images and spectroscopic studies. They could detect objects 100 times fainter than JWST, observing the first, high-red shift stars in the early universe and their assembly into galaxies. We explored the scientific opportunities, key technologies and optimum location of such telescopes. We have demonstrated critical technologies. For example, the primary mirror would necessitate a high-reflectivity liquid that does not evaporate in the lunar vacuum and remains liquid at less than 100K: We have made a crucial demonstration by successfully coating an ionic liquid that has negligible vapor pressure. We also successfully experimented with a liquid mirror spinning on a superconducting bearing, as will be needed for the cryogenic, vacuum environment of the telescope. We have investigated issues related to lunar locations, concluding that locations within a few km of a pole are ideal for deep sky cover and long integration times. We have located ridges and crater rims within 0.5 degrees of the North Pole that are illuminated for at least some sun angles during lunar winter, providing power and temperature control. We also have identified potential problems, like lunar dust. Issues raised by our preliminary study demand additional in-depth analyses. These issues must be fully examined as part of a scientific debate we hope to start with the present article.