Date: November 8, 2009

Title: Radio Astronomy: An Important Tool


Podcaster: Nitza Santiago

Organization: Columbia University Astronomy

Description: Radio astronomy is an indispensable tool used by scientists to study the Universe. Throughout the years astronomers have used it to learn more about different sources of radio emission such as stars and galaxies. It was through radio observations that scientists discovered the first planet outside the solar system, circling a distant pulsar. Additionally, scientists first discovered the cosmic microwave background using radio observations, which provided convincing evidence for the fiery birth of the Universe in the Big Bang. In this podcast, I’ll talk about what makes radio astronomy so important.

Bio: Nitza earned her B.S. in Physics and Electronics at the University of Puerto Rico at Humacao. Now she is part of the staff at Columbia University working as a research assistant. She intends to apply to graduate school to obtain a PhD in Astrophysics. Her research interests include radio observations of galaxies, galactic structure and star formation.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Angeliki Rossolatou, with gratitude to a very dear friend, who showed me the sky in another way than I was seeing (and loving) it before and made me interested in Astronomy!”


Hello everyone, and welcome to a special Sunday edition of Columbia Mondays! My name is Nitza Santiago and I am a research assistant at Columbia University in the City of New York. Today the topic of our podcast is “What makes radio astronomy so important.”

Most of us connect the word astronomy with stars, telescopes and visual “stargazing.” Using our eyes to observe the sky is an ancient activity, and it has produced many exciting and interesting results, but it is not the only way to perceive the Universe. One can star-gaze in other parts of the electromagnetic spectrum.

When we look up in the sky, we see light being emitted or reflected by galaxies, stars, and planets. Light itself is a strange entity, but for the purposes of this talk, we’ll consider light to simply be energy that is oscillating at a certain frequency which was emitted by an object. Visual astronomy, the kind of astronomy done with our eyes and Hubble Space Telescope uses light with a frequency of around 500 terahertz, that is, light oscillating 500 trillion times a second. But there are many frequencies of light bouncing around this Universe. It is extraordinary that when we look up we are only seeing a fraction of the light in the sky. Using sophisticated equipment, we are able to study many other frequencies of light that come to us from the cosmos. Radio astronomy is the field of astronomy that focuses on the lowest range of frequencies of light emitted by objects in the universe. These frequencies can be detected as low as 1MHz, only 1 million oscillations per second, far too low to be seen by one’s eye.

It started in 1931 when Karl Jansky, an engineer with Bell Telephone Laboratories, built the first radio antenna to identify an astronomical radio source. A few years later Grote Reber, an amateur astronomer, built the first single-dish radio telescope in his back yard in 1937, and pioneered much of this promising new field. From these beginnings, the new science of radio astronomy was born. However, it was not until the mid 1940’s that the astronomical community realized the importance of radio astronomy and began constructing instruments to do research.

Astronomers have employed a wide variety of designs for telescopes. Reber constructed his 32-foot parabolic antenna and over the next decade made the first observation of solar radio emission and completed the first radio map of our galaxy, the Milky Way. In 1945, astronomers from the University of Manchester constructed a 66.5-meter paraboloid at Jodrell Bank and used it to detect radio emission from galaxies outside from the Milky Way.

By 1958, an 85-foot radio dish was constructed in Green Bank, West Virginia. It was used to make significant leaps in planetary science research, yielding exciting results for Jupiter and Venus.

Meanwhile, Australian astronomers were creating a new radio telescope. In 1961 they constructed the Parkes 64-meter telescope, another successfully steerable parabolic reflector. Several years later, the radio transmissions from the 1969 Apollo 11 mission and the historic images of the first moon walk, were captured from the Parkes radio telescope.

In 1963, the largest single-dish radio telescope in the world was built in Arecibo, Puerto Rico. You may know it from the movies Contact or Goldeneye, but with this 305-meter telescope, many significant scientific discoveries have been made. In 1964 Gordon Pettengill’s team used it to determine the rotation rate of Mercury. In 1968, the discovery of the periodicity of the Crab Pulsar by Lovelace and others provided the first solid evidence that neutron stars exist in the Universe. In 1974 Hulse and Taylor discovered the first binary pulsar, for which they were later awarded the Nobel Prize in Physics.

In 1980, the Very Large Array (or VLA for short) was inaugurated in New Mexico, an array of 27 radio telescopes that work together as a single instrument. Several years later, in 1989, radio communications from the Voyager 2 spacecraft were received by the VLA telescope as it flew by Neptune. Objects that are commonly studied by the VLA include pulsars, supernova remnants, the Sun, planets, and black holes.

Nowadays, another array of radio telescopes is been built in Llano de Chajnantor Observatory in the Atacama desert in northern Chile. ALMA, the Atacama Large Millimiter/submillimiter Array will provide insights to star formation and galaxies in the early universe, as well as directly image planet formation.

The emissions that radio astronomers measure are extremely weak. Because radio astronomy receivers are designed to pick up such remarkably weak signals, these facilities are particularly vulnerable to interference from man-made emissions such as cell phones, satellites, televisions, radios and other computerized devices. This man-made technology is increasingly blocking out the signals from faint, distant astronomical sources in the same way light pollution blocks out our visual views of the stars.

Radio astronomy has provided astronomers with a view of the heavens that they could not see with their eyes alone. It has empowered astronomers to study stars, galaxies and black holes in unforeseen ways, unlocking clues about how our Universe works. As our instruments become larger and more complex, we will continue to probe different parts of the Universe in ways hidden from other regions of the electromagnetic spectrum.

This has been a podcast of Columbia University here in the City of New York.. For more information about public events of Columbia Astronomy visit Our next Columbia Monday podcast will be by Lia Corrales and David Tam on November 23rd entitled ”The Extraterrestrials in Your Back Yard”. Have a great day and keep listening

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365 Days of Astronomy
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