Listening In on Deep Space

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Since the dawn of mankind our ancestors have looked to the heavens and wondered what lay in the boundless expanse above. The light and movements from the sky have inspired countless stories, theories, and ideologies, remaining a central focus of man’s advancement toward modern intellect and understanding.

Borne from the curiosity of those earliest stargazers, humanity has built up libraries of knowledge about the cosmos, subjects so intricate and vast they would take several lifetimes for the average among us to comprehend it all. And yet for all our scientific certainties, there is still so much we do not know and cannot see. Modern telescopes have the power to peer into deep space, glancing at far off stars and galaxies, but even the sight of these distant celestial bodies begs us to push further, to seek and find that which is beyond our already fathomless field of vision.

The subject of astronomy conjures up images of scientists with eyes trained to telescopes, but as our technology has advanced, so has our collection of data from outer space—and it isn’t always visual. Astronomers can use different kinds of electromagnetic radiation to map the cosmos, most notably radio waves. Whereas optical astronomy involves looking through a telescope at the light of celestial objects (as one might imagine Galileo did), radio astronomy is accomplished through the collection of radio emissions from these objects in much the same way.

“You can think of radio waves as a flavor of light that has wavelengths your eyes can’t see,” astronomer Jim Jackson tells BTRtoday. Jackson is the head of the School of Mathematical and Physical Sciences at Newcastle University in Australia, recently relocating from Boston University in part for the access to radio telescopes Down Under. He explains that even optical astronomers no longer look through telescopes anymore; computers are the eyes, as the images are processed numerically and the data is stored digitally.

“It’s the same with radio telescopes,” Jackson says. “There are receivers at the back of these telescopes to collect the data, which are digitized, and then the computers will process those signals.”

The very idea of processing radio waves from outer space seems counterintuitive since we can’t hear them, but they do allow astronomers to look at things optical telescopes might not otherwise focus on.

“Radio waves look at colder things, or they look at radio emissions caused by moving charges like electrons,” Jackson explains. “It looks at either very energetic things like black holes, or cold gas clouds floating around in space.”

Just like the industrial versions of their optical cousins, radio telescopes are large. Until recently, the largest resided at the Arecibo Observatory in Puerto Rico, which measures more that 300 meters wide and whose dish is comprised of more than 38,000 perforated aluminum plates. The original design was completed in 1963, but it still stands as one of the most significant tributes to astronomical study around the world.

Not long ago, however, Arecibo was overtaken as the world’s largest radio telescope to the Five-hundred meter Aperture Spherical Telescope (FAST) in China’s Guizhou Province. In comparison, FAST measures 500 meters across—an enormous gap that potentially creates worlds of distance between the two.

“Think of a telescope as a bucket collecting light or radio waves, which are like droplets of rain,” Jackson says. “The bigger the bucket, the more you collect. So you can see fainter objects, which tend to be more distant or perhaps less massive than more luminous objects.”

FAST’s size also creates greater resolving power, which is directly proportional to the diameter of a telescope. “If you make a telescope twice as big in diameter, you can see twice the detail in the sky. You can separate objects, you can clear picture, you can see things that are crowded together and begin to separate them,” Jackson says.

The obstacles creating large telescopes—let alone one of FAST’s size—are legion. Environmental factors such as wind and temperature come into play, as the former can create interference while the latter can cause the large metal plates which comprise the telescope’s dish to expand and retract. This can distort the shape of the object from which radio emissions are being received.

This wasn’t lost on the designers of FAST, who knew they needed an expansive valley in order to create the space necessary for the project. That involved clearing a village of 65 people back in 2009, as well as some 9,000 more who live within three miles of the newly completed telescope.

It’s hard to imagine such a reductive measure being utilized in the United States without major uproar. Controversial though it may have been to uproot citizens, however, the difficulties of manmade radio interference were too stark to ignore with a project of this size.

“More and more, telescopes have to be built in remote sites, not because the weather’s better, but because there’s less radio interference,” Jackson says.

The idea is that this telescope will allow mankind to see further and more clearly into deep space than ever before, and certain aspects of its design accentuate that. Unlike Arecibo, which is mostly fixed and can only view objects directly overhead, FAST allows for real-time shape adjustment via the cables from which it is suspended. Its receiver moves around as well, ensuring the highest precision while allowing the exploration of larger swaths of sky.

“This is a telescope I want to use,” says Jackson, who has used a number of the world’s most powerful telescopes, including Arecibo. “The sensitivity is going to be similar to Arecibo for things that go overhead, but this one has the advantage that you can look at more of the sky. It would be better if it were further south, because then you could look at more sky, but nevertheless the ability to steer the telescope receiver around is really important.”

As Jackson sees it, FAST is a major accomplishment on many levels—in science, engineering, and in bringing another major world power into the astronomical field.

“To me, the major achievement of this telescope is that it brings China into the world astronomy game big time,” he says. “This is a huge achievement for them. It makes the international community even stronger. It’s opening up a new, powerful international partner in the field, and I applaud it.”