The coolest radio telescope around just got better. Several orders of magnitude better. It may look exactly the same as it always did to most people, but the Expanded Very Large Array (EVLA) is changing what is possible at centimeter-wave astronomy.
Astronomers around the world have used the excellent sensitivity and spatial resolution of the array to chart the movement of hydrogen gas in galaxies, study molecules in star-forming regions in our galaxy, and map active galaxies out in the universe for billions of light-years. However, with 1970s-era technology, it was time for a change.
When describing this telescope out in the plains of New Mexico, you might get a nod of recognition if you say, "It's the Y-shaped array that was seen in the movie 'Contact.'" That part hasn't changed. If you take a really close look inside each of the 27 dishes, you'll find the first big upgrade: new receivers and feedhorns.
The feedhorns literally "feed" the radio radiation that has been collected by the dish to the receiver electronics. The old style is on the left and shiny new ones on the right.
When it was dedicated in 1980, the Very Large Array (VLA) covered certain narrow frequency bands in the centimeter-wave part of the radio spectrum. These bands, or "radio colors," were often referred to by their corresponding World War II-era letter designations. The new receivers break that mold by covering all frequencies from 1 to 50 GHz and several large chunks above and below that.
More frequency coverage means better sensitivity, a factor of 5 to 20 better than the old VLA. And that's just by collecting more of the radio light that is out there. What's even better is how the signal is processed.
The EVLA has a new supercomputer at the backend, called the WIDAR correlator. Every radio interferometer needs such a computer to bring all the signals together from the individual telescopes to produce a dataset. WIDAR (or, Wideband Interferometric Digital ARchitecture) is a beast, getting its own room in the control building and a big cooling system to keep it running comfortably.
WIDAR allows for the telescope to look at large swaths of the radio spectrum at one time, which boosts the sensitivity of the array by a factor of 10. Not only that, the spectrum can be split up into as many as 4,194,304 tiny little spectral channels, so astronomers can search for the faintest spectral lines of molecules in the spaces between the stars.
National Radio Astronomy Observatory (NRAO) scientists Rick Perley, Chris Carilli and Ran Wang unveiled some key results from the early phases of the EVLA's operation at a press conference at the American Astronomical Society meeting in Boston. Unfortunately, or fortunately, I'm spending all of my time on my research project at the moment, so I wasn't able to attend, but I've been following the EVLA's progress since I was a summer student at the NRAO in 2004. In addition, some of the results are already in preprint format, so I'll be following up with an in-depth look at some of these incredible images.
When one of the world's most powerful telescopes gets even more powerful, you can expect a lot of cool images and science to come down the pike fairly quickly. The universe will be forced to reveal even more of its secrets to curious and dedicated scientists.
Image Credits: Top – NRAO/AUI/Bob Tetro; Middle, Bottom – me
