By the end of the decade, five new telescopes will be completed which are each hugely more powerful than any before them and may answer vital questions about our universe. Robin McKie hails the new space race

Astronomers are taking part in a new space race – to build the world's largest telescope. Four rival projects are now under way and should see a series of giant observatories operating on mountain tops in Hawaii and Chile by the end of the decade.

Each telescope will be at least 10 times more powerful than any operating on Earth today and will revolutionise our knowledge of the universe by peering further and further back into the dim recesses of the cosmos. Among the objects that astronomers hope to study will be the first stars and galaxies that formed after the Big Bang – the birth of the universe 13.7 bn years ago. It is also hoped the new super-telescopes will be able to spot Earth-like planets in orbit round other stars and give early warnings of asteroids or meteorites heading on a collision course with Earth.

Each instrument is scheduled for construction by around 2018. However, precise completion dates are being kept secret by each construction team to prevent their competitors from gaining an advantage.

"Being first matters," says Gary Sanders, a designer on one of the super-telescopes. "When you open a window, the first to look through it sees the most exciting things."

Sanders's observatory project is known as the Thirty Metre Telescope or TMT. The number refers to the effective diameter of the telescope's mirror and is a measure of its light gathering power. By contrast, the Keck Observatory – which is the world's most powerful at present – has two telescopes, each with a mirror that has a diameter of 10 metres.

Constructing a giant telescope is difficult, however, because a 30-metre mirror made of normal reflecting material starts to bend and distort under its own weight. The TMT designers believe they can get round this problem by creating a mirror that is made up of 492 small hexagonal segments.

The TMT will be built on Mauna Kea, in Hawaii. In the middle of the Pacific Ocean, the mountain is surrounded by thousands of miles of thermally stable seas. In addition, the 13,796ft summit has no nearby mountain ranges to disturb the upper atmosphere. Few city lights pollute Hawaiian night skies, and for most of the year, the atmosphere above the mountain is clear, calm and dry. Hence its popularity with astronomers who have already built several telescopes there, including the Keck Observatory.

By contrast, the other three super-telescopes will be built in the mountains of Chile which also benefit from having extremely clear and calm atmospheric conditions. The Large Synoptic Survey Telescope (LSST) will use a complex system of mirrors to create what will, in effect, be a super-digital camera that will be able to build up a full-colour image of the entire visible sky over a few nights. This star map will be made available to the public via Google.

Then there is the Giant Magellan Telescope (GMT) which will have seven separate mirrors, each 8.4 metres in diameter. Six will be arranged like petals around the seventh. This configuration will have the light-gathering power of a 24.5-metre telescope.

And finally, the European Extremely Large Telescope (E-ELT) will have a 42-metre mirror constructed from 1,000 hexagonal segments and should be able to gather 15 times as much light as the Keck. It will not only be able to track down Earth-like planets round other stars but detect whether they have oceans and continents.

These telescopes all exploit state-of-the-art technology: wafer-thin reflecting materials for their mirrors and highly sophisticated guidance systems that will allow several mirrors to combine the light they gather into a single image. These techniques come at a price, however, with the cost of each telescope likely to reach $1bn or more.

That may seem a hefty price for a scientific instrument. It is cheap compared to the next space telescope's price tag, however. Nasa's James Webb Space Telescope, which has 6.5-metre mirror and is set for launch in 2014, will hover in space, outside Earth's atmosphere – which blurs images – but will cost an incredible $7bn, almost twice the total for all four new ground-based observatories put together.

And of course when things go wrong on Hawaii, an engineer with a spanner or a screwdriver will be able to put things right. With its space shuttle fleet set for the scrap heap next year, Nasa will have no way to repair its new telescope if it goes wrong. In space, no one can hear you gnash your teeth.