We can’t see God, but later this month we’re going to get pretty close. On Wednesday December 22 astronomers will launch the largest and most advanced cosmic observatory ever seen. It is named the James Webb space telescope, after Nasa’s second boss, who was head of the agency under John F Kennedy and Lyndon Johnson. Two decades and £7.3 billion in the making, it will transform our understanding of the universe and our own beginnings — and possibly our search for life.
Equipped with a 6.5m gold-plated hexagonal mirror, the telescope — an international venture between Nasa, the European Space Agency (ESA) and the Canadian Space Agency — will collect more light than any other space telescope, magnifying our view of the heavens as never before, from galaxies and planets to the dawn of the universe itself. “We have built a space-time machine,” says Mark McCaughrean, senior adviser for science and exploration at the ESA.
The telescope was devised in the mid-1990s. Nasa launched the Hubble space telescope in 1990, itself a revolution in our cosmic knowledge, but already astronomers were dreaming of what might come next. Could something much grander in design and ambition be launched in the early 21st century, something that could surpass Hubble and unravel the deepest secrets of the cosmos?
The answer was the James Webb. Due to be launched in 2011 at a fraction of its present cost, the project has been beset by delays and budget overruns. That is testament not to mismanagement but to the technological leap in its design.
“We came up with a dream,” says McCaughrean. “Maybe we underestimated the difficulty of building the dream. But we made it happen.” In all, tens of thousands of people have worked on the project. A petition earlier this year to have the device renamed, because of Webb’s alleged complicity in the 1960s when federal employees at Nasa and elsewhere were fired for being gay or lesbian, was unsuccessful.
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The initial plan was to fly the telescope from its construction site in California to the launch site in French Guiana, on the northeast coast of South America. But the telescope was too heavy for the 56 miles of unstable roads from the airport to the take-off site. Instead it was shipped in October via the Panama Canal and then up French Guiana’s Kourou River, which had been dredged to ensure the ship and its heavy cargo did not get stuck. The timing of the voyage was kept secret to avoid the attention of pirates.
From here, the telescope will be launched into space and over 30 days will travel a million miles from our planet, away from our sun, beyond the moon to a region called Lagrange Point 2, or L2, where the gravity of our star and Earth cancel each other out, allowing the telescope to remain in a stable location.
En route the telescope will unfurl 18 gold-plated hexagonal mirror segments, creating its vast honeycomb-shaped mirror, protected from the sun’s glare by five tennis-court-sized blankets made of Kapton, a plastic insulating film that will keep the temperature below minus 220C.
It will also deploy its instruments and components as it travels, a nerve-racking period involving hundreds of moving parts, the failure of any one of which would end the telescope’s mission before it has begun. Then it will spend a further five months testing its instruments before its glorious observations of the universe commence. The public are due to see the first pictures next summer.
The telescope will observe the universe in infrared, allowing it to peer through dust and gas in a way other telescopes, such as Hubble, cannot: they mostly observe in visible and ultraviolet, with some near-infrared.
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The new telescope will be able to investigate the formation of planets around infant stars, squinting through the dense discs of dust and gas that surround such objects to witness the moments that newly forming worlds carve out gaps as they orbit, perhaps providing clues to how our Earth came to be.
It will look so far into space that it will act as a time machine, allowing scientists to peer back to the earliest moments of the cosmos. Some of the light it will see will have been emitted by stars nearly 13.5 billion years ago, shortly after the Big Bang.
Scientists hope to examine these first stars to form in the universe, inside the earliest galaxies. In turn, this will reveal what these galaxies looked like and how they evolved, something that simply hasn’t been possible before.
“That is something that I think is going to completely surprise us,” says Hannah Wakeford, a lecturer in astrophysics at Bristol University.
In our own solar system the telescope will perform the role of a dancing space probe, casting its gold-plated eye across our sun’s reaches. It will take detailed images of planets such as Jupiter and Saturn, but also Uranus and Neptune, worlds that have been fleetingly visited only once, by Nasa’s Voyager 2 spacecraft in the late 1980s. It will hunt for icy bodies in a region of the outer solar system called the Kuiper belt, and may be able to spy asteroids and comets from other solar systems passing through our own.
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Perhaps its showstopper, though, will be the role it plays in looking for signs of life on other worlds. The telescope will study a few known planets in other solar systems, exoplanets, in great detail. By watching as the planets drift in front of their stars, it will be able to see the light from those stars passing through any atmosphere present. That will allow some simple molecular analysis of these atmospheres to be made.
It won’t spy little green men waving from craters, but this scrutiny may unearth gases, such as carbon dioxide and methane, that could indicate a planet’s habitability.
“On our planet, most of our methane comes from life,” says Victoria Meadows, a professor in astronomy at the University of Washington in the US. “Carbon dioxide plus methane would potentially be an indicator that we [are looking at] something like the early Earth” — or possibly even a world similar to our own today.
The main focus of these studies at first will be Trappist-1, a fascinating planetary system 40 light years from our own. Here, seven Earth-sized worlds orbit a dwarf star 20 times dimmer than the sun. Yet the planets orbit closer than Mercury orbits our star — near enough that three of them are believed to be in the system’s habitable zone, where liquid water, and maybe life, could exist. “For astrobiologists it is the No 1 most important target for [the Webb telescope],” Meadows says.
All this is only a snapshot of the science that will be performed. From distant galaxies to habitable planets and much, much more, the telescope will have a transformational effect on astronomy. Just as Hubble is revered as one of the great telescopes that changed our vision of the cosmos, so will the Webb telescope be lauded. Scientific answers to questions such as where we come from and whether we are alone in the universe have never been so tantalisingly within reach.
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“We built a cathedral,” says McCaughrean. “It says something quite remarkable about bringing people together. We can solve amazing challenges if we put our minds to it.”
