Most detailed infrared map ever of our Milky Way captured

Astronomers have published a gigantic infrared map of the Milky Way containing more than 1.5 billion objects ― the most detailed one ever made. Using the European Southern Observatory’s VISTA telescope, the team monitored the central regions of our Galaxy over more than 13 years. At 500 terabytes of data, this is the largest observational project ever carried out with an ESO telescope.

“We made so many discoveries, we have changed the view of our Galaxy forever,” says Dante Minniti, an astrophysicist at Universidad Andrés Bello in Chile who led the overall project.

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 8600 full moons. The Milky Way comprises a central bulge — a dense, bright and puffed-up conglomeration of stars — and a flat disc around it. Red squares mark the central areas of our galaxy originally covered by VVV and later re-observed by VVVX: most of the bulge and part of the disc at one side of it. The other squares indicate regions observed only as part of the extended VVVX survey: even more regions of the disc at both sides (yellow and green), areas of the disc above and below the plane of the galaxy (dark blue) and above and below the bulge (light blue). The numbers indicate the galactic longitude and latitude, which astronomers use to chart objects in our galaxy. The names of various constellations are also shown. Credit: ESO/VVVX survey

This record-breaking map comprises 200 000 images taken by ESO’s VISTA ― the Visible and Infrared Survey Telescope for Astronomy. Located at ESO’s Paranal Observatory in Chile, the telescope’s main purpose is to map large areas of the sky. The team used VISTA’s infrared camera VIRCAM, which can peer through the dust and gas that permeates our galaxy. It is therefore able to see the radiation from the Milky Way’s most hidden places, opening a unique window onto our galactic surroundings.

This gigantic dataset covers an area of the sky equivalent to 8600 full moons, and contains about 10 times more objects than a previous map released by the same team back in 2012. It 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. Observing infrared light means VISTA can also spot very cold objects, which glow at these wavelengths, like brown dwarfs (‘failed’ stars that do not have sustained nuclear fusion) or free-floating planets that don’t orbit a star.

This image from ESO’s VISTA telescope captures a celestial landscape of vast, glowing clouds of gas and tendrils of dust surrounding hot young stars.

The observations began in 2010 and ended in the first half of 2023, spanning a total of 420 nights. By observing each patch of the sky many times, the team was able to not only determine the locations of these objects, but also track how they move and whether their brightness changes. They charted stars whose luminosity changes periodically that can be used as cosmic rulers for measuring distances. This has given us an accurate 3D view of the inner regions of the Milky Way, which were previously hidden by dust. The researchers also tracked hypervelocity stars — fast-moving stars catapulted from the central region of the Milky Way after a close encounter with the supermassive black hole lurking there.

The new map contains data gathered as part of the VISTA Variables in the Vía Láctea (VVV) survey and its companion project, the VVV eXtended (VVVX) survey. “The project was a monumental effort, made possible because we were surrounded by a great team,” says Roberto Saito, an astrophysicist at the Universidade Federal de Santa Catarina in Brazil and lead author of the paper published today in Astronomy & Astrophysics on the completion of the project.

This image shows a detailed infrared view of Messier 17, also known as the Omega Nebula or Swan Nebula, a stellar nursery located about 5500 light-years away in the constellation Sagittarius.

The VVV and VVVX surveys have already led to more than 300 scientific articles. With the surveys now complete, the scientific exploration of the gathered data will continue for decades to come. Meanwhile, ESO’s Paranal Observatory is being prepared for the future: VISTA will be updated with its new instrument 4MOST and ESO’s Very Large Telescope (VLT) will receive its MOONS instrument. Together, they will provide spectra of millions of the objects surveyed here, with countless discoveries to be expected. (ESO)