Astronomers want to build an ‘Ultimately Large Telescope’ on the Moon

Nasa may announce the discovery of water on the moon (Getty Images/iStockphoto)

Astronomers want to build an "Ultimately Large Telescope" on the Moon.

The equipment would allow scientists to see deep into the universe in a way no other telescope can, allowing people to study the very first stars in the universe, watching as they switched on even before galaxies were formed.

Such a time has been theoretically proposed but never directly seen, because we do not have sensitive enough equipment to see early enough in cosmic time.

But a new study suggests that building a vast telescope on the Moon would allow scientists to study stars at their very beginning. The research will be published in The Astrophysical Journal.

The proposed telescope would be built specifically so that it could be transported to the Moon, where it would sit inside a crater, spinning around and peering into the early universe.

“Throughout the history of astronomy, telescopes have become more powerful, allowing us to probe sources from successively earlier cosmic times – ever closer to the Big Bang,”  professor and team member Volker Bromm, a theorist who has studied the first stars for decades, said in a statement.

“The upcoming James Webb Space Telescope [JWST] will reach the time when galaxies first formed. But theory predicts that there was an even earlier time, when galaxies did not yet exist, but where individual stars first formed -- the elusive Population III stars.

“This moment of ‘very first light’ is beyond the capabilities even of the powerful JWST, and instead needs an ‘ultimate’ telescope.”

The stars that came into existence first are unique: perhaps as much as 100 times larger than the Sun, they were born from a mix of hydrogen and helium gasses.

The calculations in the study suggest that if a liquid mirror telescope were built on the surface of the Moon, it would be able to see them, effectively looking back in time to a point 13 billion years ago. Researchers at the University of Arizona had actually proposed a similar facility in 2008 – called the Lunar Liquid-Mirror – but Nasa did not pursue the project, amid a lack of clear science about the earliest stars and what the telescope might see.

To allow the telescope to be more easily carried, it would be built out of liquid rather than glass. Its mirror would be made out of a metallic, reflective liquid that would sit on top of a spinning vat, keeping it in the right shape so that it functions as a mirror.

An image from the original proposal for a liquid telescope on the Moon. Rather than the 20-meters shown here and in the original proposal, the ‘Ultimate’ telescope could be 100 meters in size (Roger Angel et al./Univ. of Arizona)

It would be stationary on the Moon’s surface, the researchers suggest, perhaps placed inside a crater on the north or south pole. It would keep looking at the same patch of sky, collecting as much light as possible.

“We live in a universe of stars,” Bromm said. “It is a key question how star formation got going early in cosmic history. The emergence of the first stars marks a crucial transition in the history of the universe, 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.

“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.”