Radio Astronomy in the Desert

A Visit to the Very Large Array in New Mexico

the Very Large Array radio telescope
The Very Large Array in compact configuration. NRAO

If you drive across the Plains of San Agustin in central west New Mexico, you'll come across an array of radio telescopes, all pointed toward the sky. This collection of big dishes is called the Very Large Array, and its collectors combine to make a very large radio "eye" on the sky. It's sensitive to the radio part of the electromagnetic spectrum (EMS).

Radio Waves from Space?

Objects in space give off radiation from all parts of the EMS.

Some are "brighter" in some parts of the spectrum than others. Cosmic objects that give off radio emissions are undergoing exciting and energetic processes. The science of radio astronomy is the study of those objects and their activities. Radio astronomy reveals an unseen part of the universe we cannot detect with our eyes, and it's a branch of astronomy that began when the first radio telescopes were built in the late 1920s by Bell Labs physicist Karl Jansky.

More about the VLA

There are radio telescopes around the planet, each tuned to frequencies in the radio band that come from naturally emitting objects in space. The VLA is one of the most famous and its full name is the Karl G. Jansky Very Large Array. It has 27 radio telescope dishes arranged in a Y-shaped pattern. Each antenna is large — 25 meters (82 feet) across. The observatory welcomes tourists and provides background information about how the telescopes are used.

Many people are familiar with the array from the movie Contact, starring Jodie Foster. The VLA is also known as the EVLA (Expanded VLA), with upgrades to its electronics, data handling, and other infrastructure. In the future it may get additional dishes. 

The VLA's antennas can be used individually, or they can be hooked together to create a virtual radio telescope up to 36 kilometers wide!

That allows the VLA to focus in on some very small areas of sky to gather details about such events and objects as stars turning on, dying in supernova and hypernova explosions, structures inside giant clouds of gas and dust (where stars might be forming), and the action of the black hole at the center of the Milky Way Galaxy. The VLA has also been used to detect molecules in space, some of them precursors to pre-biotic (related to life) molecules common here on Earth. 

VLA History

The VLA was built in the 1970s. The upgraded facility carries a full observing load for astronomers around the world. Each dish is moved into position by railroad cars, creating the correct configuration of telescopes for specific observations. If astronomers want to focus on something extremely detailed and distant, they can use the VLA in conjunction with telescopes stretching from St. Croix in the Virgin Islands to Mauna Kea on the Big Island of Hawai'i. This larger network is called the Very Large Baseline Interferometer (VLBI), and it creates a telescope with a resolving area the size of a continent. Using this larger array, radio astronomers have succeeded in measuring the event horizon around our galaxy's black hole, joined the search for dark matter in the universe, and explored the hearts of distant galaxies.


The future of radio astronomy is big. There are huge new arrays built in South America, and under construction in Australia and South Africa. There's also a single dish in China measuring 500 meters (about 1,500 feet) across. Each of these radio telescopes is set well apart from the radio noise generated by human civilization. Earth's deserts and mountains, each one with its own special ecological niches and landscapes, are also precious to radio astronomers. From those deserts, astronomers continue to explore the cosmos, and the VLA remains central to the work being done to understand the radio universe, and takes its rightful place with its newer siblings.