A pioneering radio astronomy facility southwest of Valencia County: The Very Large Array

(Editor’s note: This is the third part of Nature Observation Columns)

The Very Large Array (VLA) west of Socorro is a radio astronomy facility worth visiting to ponder the vastness of the Universe.

The plains of San Agustin, located about an hour southwest of Valencia County, provide unique characteristics that have been found ideal for radio astronomy. Cosmic radio waves are billions of a billion times fainter than radio waves used to broadcast information on Earth, and radio telescopes must be placed where they can collect these faint cosmic radio waves without any radio interference from nature or humans, when even small cell phones carried by visitors to the site can interfere with the radio signals from space.

The Plains are ringed by mountains, which act like a natural fortress of rock that keeps out much of the radio interference from cities. The desert climate of the San Agustin Plain is also critical to the success of the VLA.

Humidity is a real problem in radio astronomy, because water molecules distort the radio waves passing through them and also give off their own radio waves that interfere with observations at certain frequencies.

From 1973 to 1980 the National Radio Astronomy Observatory (NRAO) built the array of dish-shape antennas that dot the landscape along Route 6 between Magdalena and Datil. Each of the VLA’s 28 antennas — including the one that is a spare — is an 82-foot diameter dish with eight receivers tucked inside.

Each antenna is loaded on a 94-feet tall, 230-ton structure that can be moved among locations lined up in a three-legged “Y” pattern of rail lines from 11 to 13 miles long.

Among its discoveries, the VLA observations showed in 1991 that ice collects on the floors of deep craters at Mercury’s poles, where it can remain permanently shaded from the Sun. In 2011, astronomers found a black hole a million times more massive than the Sun in a star-forming dwarf galaxy.

Plans are underway for what is called the Next Generation VLA, or ngVLA. The antennas will have a new design and there will be 263 of them instead of 27, with all the antennas working together as one huge telescope. A prototype has been built and can be seen at the VLA site.

The ngVLA plan, to be completed in 2035 proposes to have 150 fixed antennas concentrated in New Mexico, with all 113 others placed from Hawaii to New Hampshire. The ngVLA antennas will be constructed in Socorro, providing a boost to the local economy.

The VLA can be visited daily except major holidays, and tickets for visitors can be purchased online at public.nrao.edu/visit/very-large-array/. Be prepared for spectacular views of very advanced astronomy technology.