Sense of the stars: New telescopes poised to unlock the universe

Advances in technology over the last 20 years are giving birth to a new generation of telescopes that will open up the skies.

CSIRO
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Michael Muller

For nearly as long as we've walked the Earth, humans have tried to make sense of the stars.

We've come a long way from the pits dug 10,000 years ago as a lunar calendar in a field in Scotland. Over the past 30 years alone, telescopes have helped discover the age of the universe, provide visual proof of black holes, confirm nearly 3,500 planets outside the solar system (and photograph them for the first time), see the formation of planets and reveal the life cycle of stars.

Now, three new sky-gazing tools are poised to tell us even more. Each will play a unique role in deciphering the mysteries of astronomy and astrophysics. With them, scientists will have a clearer view into the beginning of time, see the atmospheres of planets outside our solar system and explore the light and radio properties of black holes.

Mirror, mirror

For the Giant Magellan Telescope Organisation, a remote site in Chile, far from the ambient light of human habitation, will be home to the first of a new generation of extremely large telescopes. These optical telescopes will be far larger than anything we've seen to date.

With a diameter of 24.5 metres (80 feet) and a collecting area of 368 square metres (3,961 square feet), the GMT will open a new era of optical astronomy, able to capture images 10 times sharper than those of the Hubble Space Telescope. It's the culmination of decades, if not centuries, of astronomical technology.

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The Giant Magellan Telescope Organisation

The first telescopes -- like those used by Galileo Galilei in 1609 -- were known as refracting, where a convex lens at either end of a long tube magnifies the images in the night sky. Reflecting telescopes with metal mirrors came next in 1721. (William Herschel used one of these of his own invention to discover Uranus as well as Saturn's sixth and seventh moons, Enceladus and Mimas, in the 18th century.) Reflecting telescopes with glass, rather than metal, mirrors became popular in the 20th century.

Glass mirrors produce much clearer images than metal mirrors and won't tarnish as easily. But until the 1990s, their upper limit was about 5 metres (16 feet) in diameter. Any larger, and the glass would crack under its own weight. That changed about 30 years ago, when several breakthroughs made it possible to construct glass mirrors that were about 8 metres (25 feet) across.

"You could take a number of smaller mirrors, polish them as segments or sections of one parent optical surface, align them carefully and combine the light to a single focus," said Patrick McCarthy, director of the Giant Magellan Telescope Organisation.

It doesn't take too giant a leap to get from that point to using multiple mirrors to build an even bigger telescope. This is how the GMT will work: an array of seven 8.4-metre (27-foot) mirror segments that will combine into one giant reflector, cast from borosilicate glass, made from a mixture of silica and boric oxide, that doesn't have the fragility or temperature sensitivity of older glass mirrors.

GMT's mirrors are constructed. The ground is broken in Chile's Atacama Desert, one of the highest and driest spots on Earth. And the telescope is due for first light -- that magical moment when a new telescope takes its first image of the cosmos -- in 2022.

An eye in the sky

NASA and the European Space Agency's James Webb Space Telescope, scheduled to launch into Earth orbit in 2018, has a much smaller mirror. Yet, at 6.5 metres (21 feet) in diameter and with a collecting area of 25 square metres (270 square feet), it will be the largest reflecting telescope in space, outstripping its predecessor, the Hubble Space Telescope's 2.4-metre (7.8-foot) diameter reflector.

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The James Webb Space Telescope mirrors undergoing cryogenic testing.

NASA/Ball Aerospace

Space has its own set of challenges. Because of the extreme cold under which the JWST will operate, the reflector is not made out of borosilicate glass, but gold-coated beryllium, which is better able to handle these temperatures. This material has been used before, such as the Spitzer Space Telescope in orbit around the sun since 2003. But there's a bit more to the JWST.

"The science objectives drive what the engineering has to achieve. This means a very large aperture telescope -- so large that it has to fold-up to fit into its launch vehicle and hence unfold once in space," said JWST deputy project manager Paul Geithner.

"It also calls for a telescope that is exquisitely sensitive to infrared light, which means a telescope and instruments working at extremely cold temperatures to suppress self-emitted infrared energy, as well as demanding very sensitive and low-noise infrared light detectors."

All of these things, he adds, required the development of large lightweight deployable cryogenic-compatible optics, large shields that protect the telescope from the sun, improved testing facilities and big advances in infrared light detectors.

It's all about the data

Meanwhile, the Square Kilometre Array, being built by an organisation comprising 10 countries, including Australia, Canada, China, South Africa and the UK, is the world's most ambitious radio telescope project.

Planned to start making observations in Australia and Africa in 2020, the SKA will consist of radio telescope antennas that combine for a total collecting area of a square kilometre, or 1000,000 square metres (10 million square feet). This will make it the biggest telescope ever built, 10 times more sensitive than largest single-dish telescope, the Arecibo Observatory, and 50 times more sensitive than the most powerful interferometer telescope, the Jansky Very Large Array in New Mexico.

We've had the technology to build the antennas for decades. The reason it's taken so long, says George Heald of Australia's Commonwealth Scientific and Industrial Research Organisation Astronomy and Space Science division (CSIRO), is less to do with the actual telescope and more to do with data. Until now, we simply didn't have the computing power.

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The Australian Square Kilometre Array Pathfinder, a telescope array consisting of 36 antennas, both tests and demonstrates the technology that will be used in the Square Kilometre Array.

CSIRO

"One of the primary reasons that it's becoming possible now is computing. At the heart of the telescope is the computer that connects everything together. The computing capacity within this Square Kilometre Array is absolutely essential and it's now becoming feasible," he said.

"Associated with that is the data flow. There is a massive amount of data which is flowing around from the telescopes to the central computing. That data flow, in principle, surpasses global internet traffic."

By necessity, the telescope needs to be built in a remote location, far from the cell phone, GPS and wireless internet signals that will interfere with the radio data the antennas collect. Even microwave ovens can be disruptive.

That, however, presents another challenge: How do you power something on such a large scale? The CSIRO is using an on-site solar array to power the Australian Square Kilometre Array Pathfinder, a telescope constructed from 2009 to 2012 to test technologies to be deployed in the SKA.

Onwards and ever upwards

On first glance, building so many telescopes might be considered overkill, but each telescope -- the ground-based optical telescope, the orbital optical telescope and the radio telescope -- has its role in explaining the cosmos.

For instance, the JWST will be able to see much more clearly into the early universe, looking at early galaxies in the infrared with a phenomenal level of sensitivity. However, it will only be able to see from the red end of the spectrum to the infrared. The GMT will be able to detect a wider range of light, and in addition has the ability to get a sharper, wider field of view very quickly. And the SKA will look into the radio spectrum.

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Giant Magellan Telescope Organisation

"Radio and optical go very much hand in hand," Heald said. "In particular if the radio can probe the material from which stars are forming and in optical we probe the actual stars themselves then we can link the two things together and learn a lot more about the evolution of galaxies through time."

There's so much out there that is yet to be discovered. The beginning of the universe is 13.8 billion light-years distant. The Hubble Space Telescope has found a galaxy 13.4 billion light-years away. Both the GMT and the JWST are expected to be able to see as far as the Big Bang.

The exciting new field of gravitational astronomy opened by the Laser Interferometer Gravitational-Wave Observatory offers new opportunities for optical and radio astronomy too. Telescopes such as the GMT and the SKA could be used to probe the light and radio properties of black holes and colliding galaxies picked up by gravitational wave detectors.

Beyond humanity

And, of course, there's the ongoing search for extraterrestrial life. Telescopes such as the GMT are powerful enough to see the atmospheres of exoplanets. With weaker telescopes, light from the parent star renders any atmosphere too faint to be seen. Analysing the chemical signatures of these atmospheres may reveal whether or not these exoplanets are capable of supporting life.

"One of the big topics now in astronomy is trying to understand what the chemical signature life planet that had biological processes," McCarthy explained. For instance, the methane and oxygen produced by geological processes on Jupiter are in different ratios from the methane and oxygen caused by biological processes on Earth.

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Full-scale model of the JWST at SXSW in Austin, Texas, 2013.

NASA

"The detection of water, free oxygen, carbon dioxide, and methane and such in the atmosphere of a rocky planet in its parent star's 'habitable zone' [not so close to the star that it's too hot for life, not so far that it's too cold] -- these would be game-changing in our perspective of ourselves in the universe," Geithner said.

The SKA, on the other hand, would be looking for radio signals, such as those that emit from our advanced Earth civilisations. "One of the cool things that would be interesting to find would be signs of extraterrestrial intelligence. That's one of the projects that the square kilometer array will be would be looking at. It would be sensitive to civilisations within the relatively nearby region of our own galaxy," Heald said.

All three agreed that what they're most excited about is what they don't expect to find, the questions they haven't even thought to ask yet.

"The prospect of discovering the unknown and pushing back the boundaries is why I'm willing to spend more than 10 years working on the GMT, because I'm confident that for 50 years, it will contribute to science, and it will lead to new discoveries, and young people will find things that either no one thought about, or that other people told them couldn't exist," McCarthy said.

Heald added, "What often happens when we build telescopes on an entirely new scale like this is that we end up discovering things that we never anticipated. We end up finding the answers to questions that we never knew that we should be asking."

This story appears in the fall 2016 edition of CNET Magazine. For other magazine stories, click here.

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