A 'liquid-mirror telescope' on the moon could detect universe's first stars

Yes, a spinning vat of reflective liquid in a moon crater sounds awesome.

Amanda Kooser
Freelance writer Amanda C. Kooser covers gadgets and tech news with a twist for CNET. When not wallowing in weird gear and iPad apps for cats, she can be found tinkering with her 1956 DeSoto.
Amanda Kooser
2 min read
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This is the Giordano Bruno crater on the far side of the moon. A crater would be a prime place to build a lunar telescope.

NASA/Goddard/Arizona State University

NASA's much-delayed James Webb Space Telescope will be able to stare deep into the past, illuminating the birth of the universe's first galaxies. But some astronomers want to go back even further, to investigate the very first stars. A radical concept for a lunar telescope could take us there.

A team of astronomers at the University of Texas at Austin have revisited a concept for a liquid-mirror telescope on the moon that was originally floated over a decade ago, but got shelved by NASA. The researchers are set to publish a new paper on the idea in a future issue of The Astrophysical Journal.

Astronomers have theorized the very first stars formed 13 billion years ago, before galaxies came together. "This moment of first light lies beyond the capabilities of current or near-future telescopes. It is therefore important to think about the 'ultimate' telescope, one that is capable of directly observing those elusive first stars at the edge of time," said co-author Volker Bromm in a McDonald Observatory statement on Monday.

The moon telescope would be unusual, breaking from the use of solid mirrors like we see with James Webb. "The telescope's mirror would be a spinning vat of liquid, topped by a metallic -- and thus reflective -- liquid," the observatory said. Mercury is an example of a metal that works for this application. 

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This illustration shows what a liquid-mirror telescope on the moon might look like.

Roger Angel et al./Univ. of Arizona

The mirror would need to be 330 feet (100 meters) in diameter, and could be built into a lunar crater at one of the moon's poles. It could run on solar power.

A liquid-based telescope would be easier to transport to the moon than one made with more traditional materials. Its size and location would make it incredibly powerful. 

In keeping with some fun Earth-telescope naming conventions (check out the Very Large Array in the US and the Very Large Telescope in Chile), the moon observatory would be called the "Ultimately Large Telescope."

This isn't the only moon telescope concept scientists are investigating. NASA is funding research into a radio telescope idea that would transform a lunar crater into a dish. This would require using robots to deploy a wire mesh over a crater.

The first stars are the ultimate origin story. 

"The emergence of the first stars marks a crucial transition in the history of the universe," Bromm said, "when the primordial conditions set by the Big Bang gave way to an ever-increasing cosmic complexity, eventually bringing life to planets, life, and intelligent beings like us."