Blog: The digital revolution has brought a new era to radio astronomy

Dr. Keith Vanderlinde discusses the evolution of radio telescope design

The Australian Telescope Compact Array in New South Wales. VM Quezada/Unsplash

By Adam A. Lam

Why do radio telescopes look drastically different from optical telescopes? The answer, according to Dr. Keith Vanderlinde, is largely due to the large wavelengths of radio waves that these telescopes are designed to detect.

Dr. Vanderlinde—Associate Professor at the David A. Dunlap Department of Astronomy & Astrophysics and the Dunlap Institute—explored the design of radio telescopes and the future of radio astronomy at his October Star Talk with the Astronomy & Space Exploration Society.

Radio telescopes have typically appeared as massive structures of an antenna fixed to a parabolic dish. “There are two reasons that we make larger and larger telescopes,” he explained. “One is just to make a larger light bucket.” The larger surface area of the telescope’s dish, he continued, increases the sensitivity of the instrument.

The second reason stems from the challenge faced by radio telescopes in capturing images with high enough optical resolution. Resolution—the shortest length between two separate points in an image—is dependent on the colour (wavelength) of light (electromagnetic radiation) under observation, noted Dr. Vanderlinde.

The key measure of resolution, explained Dr. Vanderlinde, is the size of the “collecting area… in units of wavelengths.” Since radio waves have the longest wavelengths across the electromagnetic spectrum, he noted, radio telescopes must be built to large sizes for reasonable resolution.

This is why the Green Bank Telescope—a radio telescope 100 metres wide—still has a resolution around 20 times worse than the human eye, explained Dr. Vanderlinde. Historically, he added, the large size of radio telescopes have made the instruments vulnerable during natural disasters. Increased telescope size is also limited by prohibitive cost, he continued, along with physical space limitations.

In the 2000s, scientists and engineers began to address this challenge by designing aperture arrays. In this type of radio telescope, Dr. Vanderlinde explained, the integration of additional radio detectors boosts the instrument’s sensitivity as if the surface area of the telescope’s dish has increased. Contemporary radio telescopes, he noted, continue to harness the advantages of adding detectors in order to increase image resolution. This has made radio astronomy increasingly affordable.

“Previously, all the cost was in steel, [and] steel has been pretty stable in price,” he said. “Electronics are not stable in price; they drop drastically. If you can’t afford your telescope today, wait 18 months and it’ll cost half as much. If you can’t afford it, then wait another year and a half, and will be a quarter what it originally was.”

He continued: “Within a fairly small amount of time, you can afford to do almost anything. Because of this sort of digital revolution that we’re living in.”

To learn more about the physics behind radio astronomy, along with the impact of consumer technology on radio astronomy, you can watch our recording of Dr. Vanderlinde’s Star Talk on the ASX Society’s YouTube Channel.

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Blog: What are astronomers learning from the oldest light in the universe?

Dr. Adam Hincks discusses the history and future of research on the origins of the universe

A map of the early universe with CMB observation. NASA / WMAP Science Team

By: Adam A. Lam

Close to 14 billion years ago, the universe began with the Big Bang. A few hundred thousand years later, the oldest light in the universe accessible to us—named cosmic microwave background (CMB)—was emitted. This light, existing before the formation of the universe’s first stars, is a focus of astronomers who study the origins and evolution of the universe.

Dr. Adam Hincks, Assistant Professor at the University of Toronto with a joint appointment between the David A. Dunlap Department of Astronomy & Astrophysics and St. Michael’s College, is one such scientist.

“If you want [to study] the oldest light in the universe, you can’t look in optical wavelengths,” he said at his August Star Talk with the Astronomy & Space Exploration Society. “You can’t look using visible light that our eyes can see.”

Light, also known as electromagnetic radiation (EMR), travels at around 300,000 kilometres per second. But—as Dr. Hincks notes—EMR can be classified into different types, according to the frequency of the radiation. To visualize an example, he pictured the static of an “old analog television.” One per cent of that static you would see, he explained, is microwave radiation that originates from space.

This microwave radiation includes the CMB, which astronomers consider to be the oldest detectable EMR in the universe. At the time, Dr. Hincks explained, the universe consisted of hydrogen and helium in hot conditions at a nearly uniform density. Due to their heat, he continued, the gases emitted thermal radiation—known as CMB.

In 1964, astronomers Drs. Robert Woodrow Wilson and Arno Penzias discovered CMB with a radio telescope. “They found that no matter where they pointed this telescope at at the sky, they saw the same brightness everywhere in microwaves,” said Dr. Hincks. This reflects the uniform density of the hydrogen and helium that emitted the CMB, supporting the Big Bang Theory.

Closer to the present, in 1989, NASA launched a satellite named the Cosmic Background Explorer (COBE), which—as Dr. Hincks explained—can take precise measurements to study CMB. “It turns out that by looking at the precise details of [from observations of CMB],” said Dr. Hincks, “we can determine some pretty fundamental things about our universe.” These fundamentals the universe’s age, geometry, and composition—including the study of dark matter.

“About a quarter of the universe is made up of what we call dark matter,” he said. “This matter isn’t made up of the atoms that we know about: the atoms from the periodic table that you saw hanging in your chemistry classroom… We don’t know exactly what it is, but we know it’s there because we can very clearly see its gravitational effects.”

Dr. Hincks continued to explain the ambitious research projects undertaken by scientists and engineers across the globe to better study CMB. Highlights by Dr. Hincks include the active Atacama Cosmology Telescope, manufactured in Vancouver, Canada with the involvement of over a dozen institutions including the University of Toronto, along with the Simons Observatory currently in construction.

To learn more about the importance, history, and future of CMB research, you can watch our recording of Dr. Hincks’s Star Talk on the ASX Society’s YouTube Channel.

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