Giant Space Telescopes Could Be Made Out Of Liquid

An artist's rendering of a space telescope built with a liquid lens. (Image credit: Studio Ella Maru)

The concept of a liquid telescope mirror has been studied by astronomers for decades and is possible at a lower cost. Producing them with instruments is much more efficient than is possible today even with adaptive optical techniques.

The Fluidic Telescope Experiment (FLUTE) is a program designed to investigate using liquids to construct telescope lenses.  Professor Ermanno Borra is one of the researchers who have been working on this concept for almost 20 years. With their collaborator, Omar Seddiki, they have just found a way to solve one of the main problems in realizing liquid mirrors. A medium measuring about tens of meters in diameter, will be placed on the Moon. This technique might work with liquid mirrors even if the moon's temperature is below -130 C.

The construction of telescope mirrors has always faced difficulties, even in dead ends. First, because of the difficulty of polishing a large mirror to make it perfect and produce good quality observations. Second, larger mirrors will increasingly deform under their weight with the risk of breaking during transportation to the location where the liquid telescope is placed. Third, producing and cooling large mirrors is also not easy, and the manufacturing cost can be more than several million dollars. Lastly, the best sites for astronomical observations, for atmospheric stability and the average brightness of a cloudless night throughout the year are located only in high mountains such as the Atacama Desert in Chile. It is very impractical to carry a mirror with a diameter of more than 10 meters.

Of course, adaptive optics techniques, with large composite mirrors whose elements are mounted on jacks and controlled by a computer, make the impossible possible. Similarly, the interferometric techniques currently under development are actually very promising, just think of the results already obtained with AMBER for example.

Let's imagine for a moment a mirror 100 meters in diameter, the power of which will be 1,000 times greater than the James Webb Space Telescope, which will soon replace Hubble if all goes well. Spectacular images of the first galaxy and first star will be available. When we measure the impact that Hubble has had on astrophysics and cosmology, we begin to expect amazing and unimaginable discoveries.

Towards The Liquid Mirror Telescope

Optical lens for the Large Synoptic Survey Telescope (LSST). Credit: Farrin Abbott/SLAC National Accele

The mirror shape of this telescope is paraboloid. However, the rotating fluid takes this shape precisely. Astronomers have studied and produced liquid mercury mirrors that are not only cheaper and easier to manufacture, but also have the potential to be more perfect in terms of paraboloid shaping: a guarantee of good quality observations, with excellent resolution. Professor Borra is also known worldwide for his achievements in this field and for having clearly demonstrated the superiority of this mirror.

The ideal would be to build a giant telescope like this on the Moon. This may sound like science fiction but under NASA's Moon colonization program, this could be true. A telescope located at the south (or north) pole, and observing far hidden from the Sun, or in the crater of Mount Clavius ​​for example, would be perfect if only we found liquid that could withstand temperatures of -143 C!

The study program on this subject will be closed due to a lack of credible candidates to replace mercury. Fortunately, by taking a liquid in which we can make a thin layer of silver particles, we create a liquid mirror equivalent. All that's left is to find the right fluid.

We're not there yet but, thanks to ionic liquids, Borra and Seddiki got the expected result when the temperature was -98 C. Since there is such a wide range of ionic liquids, the -143rd drop should be possible soon enough. (Source Sekarangsayatahu semesta)