A new survey promises the most complete map of radio-emitting celestial sources ever made. It will reveal thousands of new objects after seven years of observation.
The iconic antennas of the Karl G. Jansky Very Large Array (VLA) have started scanning the sky as part of a new survey that will yield the most detailed map of celestial radio-emitting sources to date.
The VLA Sky Survey (VLASS) will require seven years of constant VLA operation (a total of 5,500 observation hours) to cover 80% of the Earth’s sky from its location in New Mexico’s desert. It will scan the sky three times, each scan separated by about 32 months, which will allow astronomers to watch sources evolve, as well as look for short-lived events.
“The recently improved Jansky Very Large Array is far more sensitive than ever, so the VLASS will provide a valuable radio deep-sky resource for the foreseeable future,” says Sarah Burke-Spolaor (West Virginia University). Burke-Spolaor has a special interest in fast radio bursts, signals emitted from unknown sources in faraway galaxies — although they last for less than a second, they’re as powerful as millions of Suns. VLASS could find more of these rare and mysterious bursts.
Astronomers expect that the survey will find around 10 million new objects, four times more than what’s currently known.
The VLA has 27 antennas, each spanning 82 feet. They can move along a Y-shaped track, each arm 13 miles long, to achieve a maximum resolution equivalent to a single dish with a 22-mile diameter. The new survey will gather cosmic radio emissions at 2 and 4 Gigahertz.
Originally built in 1973 and operated by the National Radio Astronomy Observatory (NRAO), the VLA just underwent a major overhaul that lasted a decade and finished in 2011. After its electronic components were replaced, the telescope’s sensitivity increased by a factor of 10. Each antenna now generates 100 times more data than it used to. To handle all the extra information, the telescope also received a new correlator, a supercomputer that combines the signals coming in from all the individual antennas into a single image. When it finally reopened, the VLA was renamed after Karl G. Jansky, the father of radio astronomy.
If everything goes as expected, the new survey will enable astronomers to discover and study new cosmic explosions, such as supernovae or neutron star collisions. It will also reveal supermassive black hole jets, spewing out of the center of galaxies. These observations will allow astronomers to discern details that are otherwise hidden from visible-light telescopes by clouds of dust.
“The most exciting thing for me is the very likely chance to discover something we really weren't expecting to find, like a new type of astrophysical source or explosion that is best found at radio wavelengths,” says Jason Hessels (Netherlands Institute for Radio Astronomy).
NRAO is already committed to making all the survey’s data publicly available as soon as they’re acquired. They will also make available processed data, ready for scientific use, within weeks to months after the observations are made.
“I'm super impressed with the initiative they're taking to release science-ready data products to the world within only weeks to months after the observations,” says Hessel. “Radio astronomy has been somewhat restricted to experts that know exactly how to calibrate and image the data. By lowering the bar and releasing already calibrated and imaged data products they'll ensure that the survey has the maximum possible scientific impact.”