It Took Astronomers 13 Years to Create the Biggest Infrared Map of the Milky Way

A collage of six images of colorful nebulae and star clusters in deep space. Each nebula displays varying hues of red, blue, purple, and orange with innumerable stars scattered throughout the cosmic clouds.

Astronomers using the European Southern Observatory’s (ESO) VISTA telescope have created and published a massive infrared map of the Milky Way galaxy containing more than 1.5 billion objects, the most detailed map of its kind ever.

The team used VISTA’s infrared camera, VIRCAM, over 13 years to create the map, collecting 500 terabytes of data. It’s the largest observational project ever conducted using an ESO telescope.

A vast starry sky with two prominent nebulae glowing amidst numerous stars. The nebulae exhibit vibrant hues of red, purple, and pink, with swirling patterns of gas and dust against the dark backdrop of space.
NGC 3603 (left) and NGC 3576 (right) | Credit: ESO/VVVX Survey

VIRCAM, a shortening of VISTA InfraREd CAMera, is a wide field camera. Each of the camera’s 67 million pixels covers 0.34 arcseconds. The massive camera weighs three tons and has 16 special detectors sensitive to infrared light from 0.9 to 1.2 μm.

A dense star field in the Milky Way displays numerous bright stars scattered across the dark sky. Nebulous clouds of gas and dust create intricate patterns, with hints of purple and pink hues, providing a stunning contrast to the surrounding starry backdrop.
NGC 6357 | Credit: ESO/VVV Survey/D. Minniti. Acknowledgement: Ignacio Toledo

“We made so many discoveries, we have changed the view of our Galaxy forever,” says project leader Dante Minniti, an astrophysicist at Universidad Andrés Bello in Chile. VISTA is located at ESO’s Paranal Observatory in Chile, a popular location for ground-based telescopes due to high elevations and favorable atmospheric conditions.

A star map of the Milky Way galaxy with colored grid overlays. The background shows a detailed image of the Milky Way, while constellations and celestial coordinates are marked. The grid overlays in green, red, blue, and yellow span across different sections of the galaxy.
This image shows the regions of the Milky Way mapped by the VISTA Variables in the Vía Láctea (VVV) survey and its companion project, the VVV eXtended survey (VVVX). The total area covered is equivalent to 8,600 full Moons. Red squares mark the central areas of the Milky Way covered by VVV and later by VVVX. The other squares were covered only as part of the extended VVVX survey. | Credit: ESO/VVVX Survey

Thanks to its infrared capabilities, VIRCAM can see through dust and gas spread throughout the galaxy and see radiation that would otherwise be hidden in the far reaches of the Milky Way.

A photograph of the night sky featuring a dense cluster of stars in the center, surrounded by numerous smaller stars scattered across the dark expanse of space. The star cluster shines brightly, with various colors and intensities visible against the black background.
Messier 22 | Credit: ESO/VVVX Survey

The massive dataset covers an area of the sky equivalent to 8,600 full Moons, per the ESO, and includes 10 times more objects than a similar map released by the same team in 2012. The new dataset includes “newborn stars, which are often embedded in dusty cocoons, and globular clusters — dense groups of millions of the oldest stars in the Milky Way.”

A high-resolution image of a dense star field, showcasing thousands of stars of varying colors and brightness against a dark space background. Pockets of dark, nebulous regions are visible, contrasting with the light from the myriad of stars.
NGC 6188 | Credit: ESO/VVVX Survey

The observations, which began in 2010 and comprised 420 nights, hit the same patches of the night sky multiple times to get a detailed look at a diverse range of objects and monitor their movement and luminosity changes over time. The team charted stars whose brightness changes periodically as they can be used as a sort of cosmic ruler to measure distances, providing a 3D view of the inner regions of the Milky Way that were previously obscured by dust.

The new map includes data from the VISTA Variables in the Vía Láctea (VVV) survey and its companion project, the VVV eXtended (VVVX) survey. These two related surveys have resulted in over 300 scientific articles already. Vía Láctea is “Milky Way” in Latin, by the way.

An expansive view of outer space showcases countless tiny stars scattered across a dark canvas. At the center, a vibrant nebula emits radiant blue, purple, and orange hues, surrounded by dust clouds and several brighter stars.
Messier 17, also known as the Omega Nebula or Swan Nebula | Credit: ESO/VVVX Survey

“The project was a monumental effort, made possible because we were surrounded by a great team,” explains Roberto Saito, an astrophysicist at the Universidade Federal de Santa Catarina in Brazil and lead author of the paper published in Astronomy & Astrophysics.

The scientific work concerning the groundbreaking infrared map will continue for decades and will utterly reshape the scientific understanding of the Milky Way Galaxy and the Universe beyond.


Image credits: ESO/VVV Survey/VVVX Survey/D. Minniti. Acknowledgement: Ignacio Toledo

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