This is a tremendous achievement: Astronomers using the European Southern Observatory’s VISTA telescope have created the most complete infrared map of the Milky Way, containing more than 1.5 billion cosmic objects. Created from 500 terabytes of data collected over 13 years, this map is changing our understanding of the galaxy by revealing hidden stars, moving celestial bodies and distant clusters.

A turning point in astronomy

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

“We made so many discoveries that we have forever changed the way we think about our galaxy,” says astrophysicist Dante Minniti of Universidad Andres Bello in Chile, who led the entire project.

Revealing hidden cosmic features

This record-breaking map includes 200,000 images taken by VISTA, ESO’s Research Telescope for Visible and Infrared Astronomy. The main purpose of the telescope, located at ESO’s Paranal Observatory in Chile, is to map large areas of the sky. The team used VISTA’s VIRCAM infrared camera, which can look through the dust and gas permeating our galaxy. It can therefore see radiation in the Milky Way’s most hidden places, opening a unique window into our galactic environment.

This massive data set covers an area equivalent to 8,600 full moons in the sky and contains nearly 10 times more objects than the previous map published by the same team in 2012. It often contains newborn stars embedded in dust cocoons. and globular clusters – dense groups of millions of the oldest stars in the Milky Way. Observing infrared light means VISTA can also detect very cold objects that shine at these wavelengths, such as brown dwarfs (“failed” stars that lack stable nuclear fusion) or non-rotating planets that float freely around the star.

A new dimension of galactic understanding

Observations began in 2010 and ended in the first half of 2023, covering a total of 420 nights. By repeatedly observing each area of ​​the sky, the team was able to not only determine the location of these objects, but also track how they moved and whether their brightness changed. They mapped stars whose brightness varies periodically, which could be used as cosmic rulers to measure distances.

This gave us a precise 3D view of the Milky Way’s inner regions that were previously hidden by dust. The researchers also tracked hypervelocity stars, which are fast-moving stars ejected from the Milky Way’s central region after a close encounter with the supermassive black hole lurking there.

Legacy and future prospects

The new map includes data collected by VISTA Variables during the Vía Láctea Survey (VVV) and its companion project, the VVV eExtended Survey (VVVX). “The project was a tremendous effort made possible by the presence of a great team around us,” says Roberto Saito, an astrophysicist at the Federal University of Santa Catarina in Brazil and lead author of a paper about its completion published today in the journal Astronomy & Astrophysics. of the project.

VVV and VVVX research has already resulted in more than 300 scientific papers. Once the surveys are completed, scientific study of the data collected will continue for decades. Meanwhile, ESO’s Paranal Observatory is preparing for the future: VISTA will be upgraded with the new 4MOST instrument, and ESO’s Very Large Telescope (VLT) will receive the MOONS instrument. Together they will provide the spectra of millions of objects studied here, and countless discoveries can be expected.