WHAT’S THE STORY?

FINAL testing has begun for the most powerful telescope ever built which, it is hoped, will not only provide insights into the dawn of time but also detect proof of alien life.

Scientists believe a new golden era of astronomy has begun with the ultimate testing of £7.7 billion James Webb Space Telescope (JWST), due to be launched next year. As the Hubble’s much more powerful successor, the JWST is the best chance to date of discovering life beyond Earth.

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“What we didn’t know five years ago is that perhaps 10 to 20 per cent of stars around us have Earth-size planets in the habitable zone,” said Matt Mountain, director and Webb telescope scientist at the Space Telescope Science Institute in Baltimore. “It’s within our grasp to pull off a discovery that will change the world forever.”

The JWST will be able to see further back in time than the Hubble — back to the light created after the Big Bang by the very first stars and galaxies.

“This is potentially a game-changer,” said physics and astronomy professor Paul Delaney of Canada’s York University. “If it is operating properly for four or five years, [it] could literally revolutionise many of the fundamental questions in astronomy – many of which have only been asked in the last 10 or 20 years since Hubble.”

HOW DOES IT WORK?

ALONG with the European Extremely Large Telescope, scheduled to begin its work in 2024, the JWST could provide “awe-inspiring images that give an idea of how small we are in the universe”, according to astronomer Daniel Brown of Nottingham Trent University.

“We are replaying looking at us in the early, early, earliest beginnings,” he said.

While the Hubble uses ultraviolet and optical wavelengths to gather information about the universe, the JWST will study space mostly in infrared, which will enable it to peek through the dust that obscures newly formed planets and stars and reveal what lies underneath. This means it will be able to gather seven times more information from the universe’s distant reaches than the Hubble.

As the telescope will be operating at about 225 degrees below zero Celsius, its 6.5 metre primary mirror has just been sealed in a giant freezer in Houston for 100 days of cryogenic tests to make sure its scientific instruments can cope.

The massive thermal vacuum chamber is so huge that it will take 10 days to suck the air out and around a month for the temperature to sink low enough for the tests.

IS IT NEW?

CHAMBER A at NASA’s Johnson Space Centre was previously used to test the Apollo spacecraft and is so big that its door alone weighs 36 tonnes.

“If there is a problem, we want to know about it right now,” said Delaney. “One side of it facing away from the sun is going to be literally at the temperature of space. The other side facing the sun will be gently cooked at a couple of hundred degrees.”

Several innovative technologies have been developed for the JWST. These include a primary mirror made of 18 separate segments that unfold and adjust to shape after launch. The mirrors are made of ultra-lightweight beryllium.

The biggest feature is a tennis court sized five-layer sunshield that attenuates heat from the sun more than a million times. The telescope’s four instruments – cameras and spectrometers – have detectors that are able to record extremely faint signals. One instrument, the NIRSpec, has programmable microshutters, which enable observation up to 100 objects simultaneously and the JWST also has a cryocooler for cooling the mid-infrared detectors of another instrument (MIRI) so they can work.

WHAT WILL IT ORBIT?

UNLIKE the Hubble Space Telescope, the JWST will not be in orbit around the Earth but will actually orbit the sun, 1.5m kms away from Earth at what is called the second Lagrange point or L2. This lets the telescope stay in line with Earth as it moves around the sun and allows the satellite’s large sunshield to protect the telescope from the light and heat of the sun.

JWST is an international collaboration between NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA). It will be launched next October, six years before the European Extremely Large Telescope (E-ELT) which began construction last month at a 3,000m high site in Chile’s Atacama desert.

The latter will be able to provide images 15 times more exact than those taken by Hubble as it will be able to gather eight million times more light from space than the first telescope invented in 1610 by Galileo.

Hopes are high that the information it collects will revolutionise astronomy.

“It is possible that E-ELT will find evidence for life on other worlds,” said Tim de Zeeuw, director of the European Southern Observatory.