Revolutionary New Radio Array Will Capture Unprecedented Images

For all the pretty pictures that optical telescopes have provided over the decades, there remains a burgeoning, but underappreciated area of astronomy that is finally on the cusp of getting the recognition it deserves. And that is radio astronomy. Astronomy that observes in the radio portion of the electromagnetic spectrum, ranging from 1 Hz to 3000 GHz.

Anyone who has seen the film “Contact” is acquainted with how astronomers use large moveable radio dishes to search for potential radio signals from far-flung extraterrestrial civilizations. But what is less appreciated is that radio astronomers now have the capacity to make images from their observations that have even better resolution than the best optical telescopes.

People don’t understand that we make images, Eric Murphy, project scientist for the Next Generation Very Large Array (ngVLA), told me by phone from Charlottesville, Va. We’re studying the same astrophysical phenomena but at different parts of the electromagnetic spectrum than at optical wavelengths, he told me from his office at the National Radio Astronomy Observatory (NRAO) headquarters.

To that end, astronomers are eagerly awaiting the NRAO’s ngVLA which will replace the observatory’s existing Very Large Array (VLA) outside of Socorro, New Mexico. Among other things, it will have ten times the sensitivity and ten times the resolution of the existing VLA whose 27 dishes have been operational since 1980.

The ngVLA is not a VLA upgrade, but rather the construction of a completely new flagship radio telescope on the high desert plains of St. Agustin, says Murphy.

Its 244 (18-meter) antennas will cover microwave frequencies ranging from 1.2 GHz to 116 GHz and will be spread over 8,860 kilometers. Some 19 (6-meter) dishes will make up a short-spacing array at the heart of the telescope. The array will also include stations in other locations throughout the state of New Mexico, west Texas, eastern Arizona, and northern Mexico.

Current estimates for ngVLA are roughly $2.3 billion for construction with an annual operational budget of $93 million, 75-percent of which will be paid by the U.S. National Science Foundation. The remainder will come from outside partners.

Full construction could begin by 2027 with full scientific operations by 2037.

At any given time, the ngVLA antennas will move data volumes equal to some 20 percent of the entire internet back to a central signal processor, says Murphy. From there, the data will be digested and turned into what he terms high level products for science.

As for the two or three most important science drivers for the ngVLA?

Terrestrial planet formation: Unveiling the formation of solar-system analogs on terrestrial scales, says Murphy. Being able to study the formation of earthlike planets in hundreds of nearby solar system analogs on scales smaller than the distance between the Earth and the Sun, he says.

Astrochemistry: Being able to detect predicted, but as yet unobserved, complex prebiotic molecules that are the basis for our understanding of chemical evolution toward amino acids and other biogenic molecules, says Murphy.

Merging supermassive black holes: Having the ability to identify and characterize the physical properties of gravitational wave sources such as merging supermassive black holes before they merge, says Murphy. No other existing or planned facility will have the capability to achieve this, he says.

Current state of the art ground-based gravitational wave detectors will get a heads up before two such supermassive black holes actually touch each other, says Murphy. Thus, the ngVLA would be able to look at these sources and watch them merge, he says.

How has technology advanced since the original VLA was constructed?

The electronics and digitizing of the systems is where much of the efficiencies and sensitivities has been gained, says Murphy. But with ngVLA, we are also trying to make high precision antennas more cheaply to allow us to buy more of them, he says.

Since the 1980s, data processing has been turned on its head.

Today, we’re not just giving raw data to folks, says Murphy. We’re actually giving them data products so they can do their science, he says. You don’t need to be a radio expert to use the telescope or to take the data from the telescope and analyze it, says Murphy.

ngVLA will also be able to observe different targets at the same time then use a correlator on the backend that will receive all the data and keep it separate. The data will then be processed independently for various users.

That’s not possible with optical astronomy, says Murphy.

The top science driver is studying terrestrial planet formation, says Murphy. We’ll be able to watch earthlike planets forming in distant solar systems as protoplanetary material evolves in real time, he says.

ngVLA will also allow us to trace the influence of chemistry on the physical evolution of a system from a molecular cloud to a solar system, says Murphy. It will enable the detection of predicted, but as yet unobserved, complex prebiotic species that are the basis of our understanding of chemical evolution towards amino acids and other biogenic molecules, he says.

As for the biggest technical challenge?

These molecules are likely precursors to biogenic molecules, says Murphy. But to detect them you literally have to sort through millions of lines of high frequency spectra, he says.

Astrochemistry and detection of prebiotic molecules will really drive most of ngVLA’s computing, says Murphy. To look for molecular line transitions of these very long chain, carbon molecules in space, you need to sift through all these narrow lines over millions of channels, he says.

These prebiotic molecules have line features that are spread densely throughout our observing range, says Murphy. To process that volume of data will require a system that is equivalent to one of the most powerful supercomputers in the world today, he says. But the expectation is that when we are up and fully running in the late 2030s, this should not be problematic, Murphy notes.

And for fans of the film “Contact”?

SETI (Search for Extraterrestrial Intelligence) astronomers will use the ngVLA to search for E.T.’s own radar, communications and propulsion emissions. The hope is that the ngVLA will enable the detection of such hypothetical offworld technology out to unprecedented distances.

Even though radio SETI will not be the ngVLA’s first priority, who knows what this new technology might find lurking around other sunlike stars?

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