Liquid magnetic telescopes

Jessica Chung. 06/01/2022

A small magnet is used to manipulate ferrofluid into unique modifications. (NASA)

Space research is constantly developing and expanding, and from Earth, the main source of our data is the telescopes that we’re able to use. While we’ve been able to acquire some amazing data with everything from radio to ultraviolet telescopes, there’s always room for improvement.

When it comes to telescopes, the bigger the better - the wider the lens, the more light you’ll be able to collect. Thus, your images will be higher resolution and your data will be clearer. Unfortunately, though, this means that one day we’ll approach some limit to what size telescope we’re able to build, cast into metal, how much weight a telescope will be able to support on its own, or how much money we’re willing to invest into solving all of these problems.

Another issue with a few telescopes is that Earth’s atmosphere often distorts telescope images that astronomers take. Recognized as early as Newton’s time, this is because as the atmosphere consists of a variety of temperatures, trying to take a photo through all of these layers often results in the light collected from the telescope going in slightly different directions depending on where in the atmosphere it passed through. The photo ends up distorted in ways that are hard to fix, especially because it’s not a consistent discrepancy over the entire thing.

There’s a solution that answers both of these problems: liquid magnetic telescopes. The concept behind these telescopes is, in essence, simple: it uses the idea of liquid mirrors, often made out of mercury, to create a telescope surface that can be manipulated as the user pleases. This idea can be expanded upon by making the liquid mirror out of something called ferrofluid, a magnetic liquid made of tiny particles that allow it to act as a liquid in the presence of magnets and as a solid otherwise. This power is perfect for these types of applications: it would allow the surface of telescopes to be specially adjusted to offset the distortion from the atmosphere while also being affordable.

In general, liquid mirror telescopes work by spinning the liquid fast enough that it creates a parabolic shape, which happens to be exactly what you need for a telescope - an idea first developed by Isaac Newton. This kind of stable rotation requires something like an electric motor in order to work, and means that they can only work if placed directly vertically, unlike conventional telescopes, which can orient themselves to look across the sky. However, this isn’t actually as inhibiting as you might think since if we’re looking for faraway objects like distant galaxies, you can find those no matter what part of the sky you look at - so for collecting general data, having these kinds of telescopes will be just fine.

In 2005, Paul Hickson worked with a few other scientists to develop the Large Zenith Telescope, or LZT, with the goal of developing liquid mirror technology that could rival the telescopes that had already existed at that time. It cost about a million dollars, significantly less than traditional telescopes of the same size (only about 1% of the cost). So, if resources were dedicated to building more instruments with this type of technology, astronomers would be able to benefit from significantly more observing time.

The LZT is the third largest optical telescope in the North America. In it, a rotating steel truss and 30 adjustable pads support a 6 centimeter thick dish of hexagonal segments that form a shell to hold a thin layer of liquid mercury. There are walls on the edge of the dish so that the mercury doesn’t spill over the sides. Pressurized air is used between the truss and its bearings in order to minimize friction and allow the telescope to spin as fast as possible.

In liquid mirror telescopes made with ferrofluid, the ferrofluid consists of extremely small particles of magnetite (Fe3O4), each about 10 nm in diameter, which can be magnetized. The ferrofluid sits above several magnetic coils, so by controlling the current and magnetic field of each of these coils, the shape of the surface can be altered. A few researchers investigated this hypothesis through testing if the mirror could account for misaligned lenses (based on incoming light), as well as creating aberrations by placing Petri dishes in front of the mirror. The liquid mirror succeeded in correcting the distortion in both of these cases.

We’ve been trying to learn more about the sky and the stars ever since early civilizations, myths about the stars that humans have written since the beginning of time. Especially with the threat of climate change looming over us, the prospect of finding more about outer space is ever appealing, and we’ll need a viable way to learn more about it. While it’s possible to keep investing resources to build bigger and bigger telescopes that require more and more resources, it’s also quite possible that liquid magnetic telescopes are a cheaper and more reasonable alternative to keep sweeping the skies.

According to Atlas Obscura, NASA hopes to develop extracurricular liquid telescopes that could be placed on the moon. Besides that, there are plenty of other applications including cosmology, the structure of the universe, the evolution of galaxies, and supernovas. It’s a worthwhile investment to consider as the study of astronomy continues to expand.

Cover Photo: (NBC News)

Jessica Chung