100m Liquid Telescope To Be Placed On The Moon

Moon Crater
Image Credit: NASA

An international team of astronomers want to build a 100 meter in diameter telescope on the Moon. No this is not the plot of some sci-fi movie, it is very much something that could happen in the next decade!

Telescopes with Liquid Mirrors

Liquid mirrors are extremely simple in their design, all you need to do is slowly rotate a container of reflective material and gravity will turn it into a perfect parabola thanks to the Coriolis effect. This concept was even known to Isaac Newton, who invented parabolic mirrors for astronomical observations. These telescopes have been, and still are, used in professional astronomy.

On Earth, these mirrors are made out of mercury, the famous liquid metal that got a very bad reputation in recent years. These telescopes sit in a wind free environment and rotate at a very slow, but constant speed. For example, the largest mercury telescope (a 6-meter in diameter telescope called the Large Zenith Telescope) would rotate 8.5 times in one minute. This comes down to about 3 km/h or 2 mph.

The upside of these mirrors is that they are extremely cheap compared to solid mirrors, mainly due to the fact that no complicated mounts need to be constructed to make it work. The Large Zenith Telescope only cost 1 million dollars, a few percent of the budget of a similar sized solid mirror telescope. The down side is that these telescopes can only look straight up, since these mirrors can never be tilted. Of course various solutions exist, similar to the way that the now decommissioned Arecibo telescope pointed with its secondary receiver.

The Lunar Liquid Mirror Telescope

The proposed lunar telescope is named the Lunar Liquid Mirror Telescope (LLMT), but has been nicknamed the “Ultimately Large Telescope”, as a nod to the 42m “Extremely Large Telescope” that is currently built to replace the 8.2m “Very Large Telescope”.

Unlike its terrestrial cousins, this telescope would not be made of mercury but a novel material called an ‘ionic liquid’. This is mostly done due to the fact that mercury is incredibly heavy and would rapidly evaporate when exposed to Lunar vacuum. The ionic liquid on the other hand is just slightly more dense than water and can be coated with a microscopic layer of silver to prevent it from evaporating at all.

The telescope would be located inside a permanently dark crater near the Lunar pole, which will cool it to cryogenic temperatures and keep it relatively safe from debris. Solar panels can be set up outside of the crater to power the motor and remote control equipment.

This telescope would be able to peer back in time to when the universe was very young, and able to see the very first generation of stars roughly 13 billion years ago. Technically it is also possible, and all materials for this telescope could be transported in a single Ares 5 rocket, which could happen as soon as the next decade.

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