The Very Large Array Sky Survey (VLASS)

Mapping the Radio Universe

Most of the marvels of the universe are invisible to us without technological assistance. Visible light is only a small slice of the electromagnetic spectrum, ranging from tiny, high-energy gamma rays to long radio waves. So, imagine if you could put on radio glasses to view a range of light obscured from all but the most sophisticated telescopes. What would you see? You might be able to peer through dusty clouds and view the beginning stages of star formation or watch the intermittent lighthouse bursts from pulsars, if the neutron star happens to be pointing towards earth at the right angle. What would it be like to see an array of energetic particles dancing around the Sun’s corona?

On September 7, 2017, the Jansky Very Large Array (VLA) pointed its antennas toward the northern sky and began one of the largest all-sky radio observations in 40 years. From its vantage point in New Mexico, the VLA Sky Survey (VLASS) will map 80 percent of the sky in 3 phases over 7 years and is expected to catalog approximately 10 million new radio sources. The survey will collect data from powerful, cosmic sources that will allow the scientific community to image supernovae explosions, gamma-ray bursts, and the collisions of neutron stars that are obscured from visible-light telescopes by thick clouds of dust. The VLA’s ability to see through dust and clouds will make the survey an important tool in the discovery of new radio objects.

Optical Sky Milky Way Galaxy

9/7/2017 - The beginning. Move through each slider to visualize the multilayered view of sky we'll be observing over 7 years.

Epoch 1.1 B September 13, 2017 - January 29, 2018

The first observations in configuration B. As the sky survey progresses and we collect more data, we'll be able to compare this view 3 times over!

Epoch 1.1 BnA February 02, 2018 - February 19, 2018

Hybrid Configuration BnA. The telescopes gather data from two different vantage points, allowing us to balance the quality of the total image.

Epoch 1.2 B January 23, 2019 - June 03, 2019

There are 3 epochs over 7 years. Within 1 epoch we collect data four different ways in order to cover 80 percent of the sky.

Epoch 1.2 BnA June 07, 2019 - June 24, 2019

End of 1st Epoch.

Epoch 2.1 B May 27, 2020 - October 05, 2020

Beginning of Epoch 2. We expect to discover powerful cosmic explosions, such as supernovae, gamma ray bursts, and the collisions of neutron stars. This new cycle will allow us to monitor any change in the radio sources.

Epoch 2.1 BnA October 09, 2020 - October 26, 2020

The midpoint.

Epoch 2.2 B September 29, 2021 - February 14, 2022

All data is publicly available as soon as it passes quality assurance.

Epoch 2.2 BnA February 18, 2022 - March 07, 2022

At this point in the survey, we've viewed 80 percent of the sky twice over.

Epoch 3.1 B February 01, 2023 - June 12, 2023

Beginning of Epoch 3. We have two reference surveys in which to compare radio sources.

Epoch 3.1 BnA June 16, 2023 - July 03, 2023

Hybrid Configuration 3.1 BnA.

Epoch 3.2 B May 29, 2024 - October 07, 2024

The Penultimate View!

Epoch 3.2 BnA October 11, 2024 - October 28, 2024

THE END! Now, we have 3 complete, in-depth views over 80 percent of the sky. Data from all three phases will be combined to make even more detailed images.

Sky Surveys have been integral to astronomy for millennia.  As far back as the 2nd century BC, Hipparcos and astronomers of the Han dynasty have observed and recorded astronomical phenomenon and seasonal celestial changes from the night sky. Sky surveys are a way to map, in a systematic way, the universe and its constituents parts, opening up the observational impact of how celestial objects, especially those beyond our solar system, change with time. Within the last century, as technology has allowed for the expansion of observations beyond the traditional visible wavelength window, sky surveys have proved to be a fundamental part of multi-wavelength astronomy.

The Very Large Array Sky Survey (VLASS) represents our third radio survey project in the last twenty years. The VLA has undergone a complete technical transformation, since our last two surveys: the NRAO VLA Sky Survey (NVSS) and Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) in 1992. From 2001-2012, the original electronic system, designed and built during the 1970’s, has been replaced with state-of-the-art technology that vastly expanded the VLA’s observing capabilities. This major upgrade has transformed the VLA into a completely new scientific tool. Our next generation sky survey will harness the tremendously improved capabilities of the VLA, resulting in a unique and extremely valuable tool for frontier research over a diverse range of scientific fields.

VLASS is designed to produce a large collection of radio data available to wide range of scientists within the astronomical community. Our science goal is to produce a radio, all-sky survey that will benefit the entire astronomical community. As VLASS completes its three scans of the sky separated by approximately 32 months, new developments in data processing techniques will allow scientists an opportunity to download data instantly on potentially millions of astronomical radio sources. This data from all three cycles will be combined to make even more detailed radio images, creating the largest-ever celestial radio census.  Scientists will be able to compare images from the individual observation cycles, allowing for the discovery of newly-appearing sources or short-lived (transient) objects.

Fundamentally, astronomy is about exploring — making images of the sky to see what is out there, and our VLA sky survey is a new and powerful resource for this exploration.

VLASS Configurations

B Configuration

The antennas in the Very Large Array are used like the zoom lens in a camera. When they are in the B configuration, the telescopes extend over the 11 kilometers (7.08 mile) length of each arm. In this configuration, we have the second largest magnification and can see great detail. The size of the array gradually decreases with the C configurations until, in the D configuration, the telescopes are all placed within 0.6 kilometer (0.4 mile) of the center.

BnA Configuration

The BnA is a hybrid configuration. The north arm of the array is extended out into the A configuration location. This allows the VLA to image objects closer to the horizon.

The iconic “Y” shape of the VLA has a specific function. The wider an array, the bigger its eye is, and the more detail it can see out in space. The VLA’s unique shape gives us three long arms of nine telescopes each. It also gives our scientists the flexibility of stretching the arms when we need to zoom in for more detail. 

Check out these videos for more information on the different VLA configurations and the amazing machines that move the 230 ton antennas around.

Featured Sky Survey Image

The sharpest radio view ever made of such a large portion of the sky. A brand new galaxy has been discovered in radio wavelengths with the VLA Sky Survey! The galaxy, classified as 6C B191505.9+674609, resides near the constellation Draco in the northern hemisphere. No sources were detected in the optical (blue) or infrared (orange) images. The green, radio image from our last survey depicts a faint source – we know something was there. VLASS has the sensitivity to reveal the distinct features of the radio lobes from a supermassive black hole found at the heart of some galaxies!

VLASS Comparison

VLASS Blog