Telescope captures most detailed infrared map of our Milky Way ever

Astronomers have released a massive infrared map of the Milky Way containing more than 1.5 billion objects, the most detailed ever made. Using the European Southern Observatory’s VISTA telescope, the team has been monitoring the central regions of our galaxy for more than 13 years. At 500 terabytes of data, it is the largest observational project ever carried out with an ESO telescope.

An article detailing the results is published in the journal Astronomy and astrophysics.

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

This record-breaking map comprises 200,000 images taken by ESO’s Visible and Infrared Survey Telescope for Astronomy (VISTA). Located at ESO’s Paranal Observatory in Chile, the telescope’s primary objective is to map large areas of the sky. The team used VISTA’s VIRCAM infrared camera, which can peer through the dust and gas that permeate our galaxy. It is therefore able to see radiation from the Milky Way’s most hidden corners, providing a unique window into our galactic environment.

The massive dataset covers an area of ​​the sky equivalent to 8,600 full moons and contains about 10 times more objects than a previous map published by the same team in 2012. It includes newborn stars, often buried 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 cool objects that shine at these wavelengths, such as brown dwarfs (failed stars that do not have sustained nuclear fusion) or free-floating planets that do not orbit a star.

Observations began in 2010 and ended in the first half of 2023, for a total of 420 nights. By observing each part of the sky multiple times, the team was able to not only determine the location of these objects, but also track their movement and whether their brightness changes.

They mapped stars that change brightness periodically and can serve as cosmic rulers for measuring distances. This allowed us to get a precise 3D view of the Milky Way’s inner regions, which were previously hidden by dust. The researchers also tracked hypervelocity stars, fast-moving stars that are catapulted out of the Milky Way’s central region after a close encounter with the supermassive black hole that lurks there.

The new map contains data collected as part of the VISTA Variables in the Vía Láctea (VVV) survey and its complementary 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 Federal University of Santa Catarina in Brazil and lead author of the study.

The VVV and VVVX surveys have already produced over 300 scientific papers. Now that these surveys are complete, scientific exploration of the collected data will continue for decades to come. In the meantime, ESO’s Paranal Observatory is preparing for the future: VISTA will be upgraded with its new 4MOST instrument and ESO’s Very Large Telescope (VLT) will receive its MOONS instrument. Together, they will provide spectra for millions of objects studied here, with countless discoveries to look forward to.