Astronomers are advocating for a massive liquid mirror telescope built directly on the Moon to observe the Universe's earliest stars.
Population III stars, the first to ignite a few hundred million years after the Big Bang, formed from primordial hydrogen, helium, and lithium. Heavier elements were later forged in their cores and those of their descendants. What did these pioneering stars look like, and how did they shape cosmic evolution?
Detecting them remains a profound challenge. Upcoming observatories like the James Webb Space Telescope (JWST) promise unprecedented views, yet even JWST may struggle to capture their faint, redshifted light.
To address this, astronomers propose a Moon-based telescope, an idea first floated in 2008 by University of Arizona researchers. NASA evaluated it then but shelved it due to limited Population III science at the time.
A lunar site offers pristine observing conditions, free from Earth's atmosphere and light pollution. The team envisions a liquid mirror telescope—a cost-effective, lightweight alternative to traditional glass mirrors for space transport.
Picture a 0.5 to 1 mm layer of mercury in a rotating parabolic container. Precisely balanced rotation creates a stable, perfectly parabolic surface where no liquid molecules shift relative to each other, yielding an exceptional optical mirror.
Positioned at a lunar pole inside a crater, the mirror would span at least 100 meters. Powered by a nearby solar array, it would relay data via lunar orbiters to Earth.
Dubbed the "Ultimate Large Telescope," this instrument would stare at one sky patch to gather maximal light, revealing these stars as "mini-halos." It's currently a conceptual proposal; lunar dust poses a key challenge.
Meanwhile, NASA's NIAC program explores converting a lunar crater into a radio telescope, potentially unlocking new cosmological insights into the early Universe.
