The Moon as a Platform for Astronomy: Radio Astronomy, Telescopes and the Search for New Phenomena

After more than forty years, our closest space neighbor – the Moon – is once again becoming the center of interest for astronomers and scientists from many other fields. Dozens of missions organized by space agencies from all over the world are preparing for Earth’s only natural satellite. Most of these will involve small robotic probes, but NASA’s ambitious Artemis program aims to return humans to the surface of the moon by the middle of this decade.

All of these activities have different reasons, including geopolitical and the search for lunar resources, such as water ice at the lunar poles, which can be mined and converted into hydrogen and oxygen rocket fuel. The planned missions will also be of great benefit from a scientific point of view. The moon can tell a lot about the origin and development of the solar system and also has great scientific potential as a platform for astronomical observations, reports Gizmodo magazine.

Telescopes on the Moon

The moon’s potential role for astronomy was discussed earlier this year at a meeting of Britain’s Royal Society. The impetus for the meeting was, among other things, the improvement of access to the lunar surface, which is now emerging. Several astronomical fields can benefit from it. First of all, it is radio astronomy – radio astronomy research could be carried out from the side of the Moon that is permanently turned away from the Earth.

The dark side of the moon it is permanently shielded from radio signals generated by terrestrial instruments. It is also protected from the Sun during the moonlit night. These properties make it probably the “quietest” place in the entire solar system, as no other planet or moon has its side permanently turned away from Earth, making it an ideal location for radio astronomy.

Radio waves are a form of electromagnetic energy, just like, for example, infrared, ultraviolet or visible light. They are defined by having different wavelengths in the electromagnetic spectrum. Radio waves with a wavelength longer than 15 meters are blocked by the Earth’s ionosphere, but reach the surface of the Moon without obstacles. For astronomy, it is the last unexplored region of the electromagnetic spectrum.

Observing space at these wavelengths falls under “low-frequency radio astronomy”. You can in them in a unique way explore the structure of the early universe, especially the cosmic “dark age”, i.e. the period before the formation of the first galaxies. The far side of the Moon may be the only place we can study it.

A pristine platform

At a recent meeting of the Royal Society, astronomer Jack Burns summarized the relevant scientific context and labeled the far side of the Moon as “a pristine, quiet platform for making low-frequency observations of the dark ages of the early universe, as well as space weather and magnetospheres associated with habitable exoplanets”.

Another potential use of radio astronomy may be to detect radio waves from charged particles trapped in the magnetic fields – magnetospheres – of planets orbiting other stars. That would help assess how capable these exoplanets are of hosting life. Radio waves from exoplanet magnetospheres would probably have wavelengths greater than 100 m, so they require a radio-quiet environment.

A similar argument can be made in the case of attempts to detect signals from potential aliens. And thanks to the opening of an unexplored part of the radio spectrum, there is also the possibility of discovering new phenomena. We should know the potential of these observations when NASA’s LuSEE-Night mission lands on the far side of the Moon in 2025 or 2026.

Instead of a satellite, a telescope in the crater

The moon also offers other possibilities for astronomy. Astronomers have extensive experience with optical and infrared telescopes operating in free space, such as the Hubble Telescope and the James Webb Space Telescope. However, the stability of the lunar surface can bring additional benefits to these types of instruments.

In addition, there are craters on the lunar poles that do not get sunlight. Telescopes observing space at infrared wavelengths are very sensitive to heat and therefore must operate at low temperatures. For example, the James Webb Space Telescope needs a huge sun visor to protect it from sunlight. On the Moon, this shield could provide a natural crater rim for free.

The Moon’s low gravity may also allow the construction of much larger telescopes than is possible with satellites. These considerations led astronomer Jean-Pierre Maillard to suggest that The moon may be the future of infrared astronomy. The cool and stable environment of permanently shadowed craters may also have advantages for a new generation of instruments to detect gravitational waves—the “ripples” in spacetime caused by processes such as star explosions and black hole collisions.

For these reasons alone, astronomy can benefit from the current renaissance of lunar research. It will likely profit from the infrastructure built on the Moon in connection with its continued exploration. This will include both means of transport – rockets, landing modules and other vehicles for access to the surface, as well as humans and robots who will construct and maintain astronomical instruments on site.