ESO Press Release 2413 – 26 September 2024
“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 [and the Vatican Observatory] who led the overall project.
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 [1] 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.
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 [2]. 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 [3] 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.
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
Vatican Observatory Astronomers on the research team
Dante Minniti is Professor and Director of the Astrophysics Doctorate at Universidad Andrés Bello, Chile, and an adjunct scholar with the Vatican Observatory.
Until 2014 he was Professor at the Department of Astronomy and Astrophysics at Pontificia Universidad Católica in Chile. He did the undergraduate studies in Astronomy at the Universidad de Córdoba (Argentina), and obtained his PhD in 1993 at the University of Arizona (USA) and on 1998, another PhD at the Universidad de Córdoba (Argentina). He was Postdoctoral Fellow of the European Southern Observatory in1993-1996, and a Lawrence Livermore National Laboratory Postdoctoral Fellow in 1996-1998. He is a member of the MACHO Collaboration since 1996, and of the SuperMACHO Collaboration since 2001.
Rev. David A. Brown, S.J. completed his doctoral studies in astrophysics at the University of Oxford in England in 2008. His thesis dealt with exploring binary star interactions in different environments (metallicities), which might produce subdwarf B (sdB) stars, and their possible implications for various phenomena including the UV-upturn. Fr. Brown joined the Vatican Observatory in November 2008, where he continues to work on various aspects of stellar evolution. He also serves as caretaker of the telescopes of the Vatican Observatory in Castel Gandolfo.
Rev. Richard A. D’Souza, S.J. graduated with a degree in Physics from St. Xaviers’ college in Mumbai in 2002, and received his Masters in Physics from the University of Heidelberg, where he worked at the Max Planck Institute for Astronomy for his thesis work.
In 2012, he started his doctoral studies in Astronomy at the Max Planck Institute for Astrophysics, in Garching, Munich, graduating in 2016. In 2016, he joined the staff of the Vatican Observatory.
He researches the formation and evolution of galaxies – in particular, through observations and simulations.
Click to view the very large list of all research team members.
I reached out to Fernando Comerón, Deputy Director for Science at European Southern Observatory, for a comment:
“As you may have read in the announcement, the VISTA telescope will be updated with a new instrument, 4MOST. In fact, rather than upgrading, 4MOST is replacing VIRCAM, the infrared camera with which those gigantic surveys were made. This will finally make honor to the full name of the telescope, as VISTA stands for “Visible and Infrared Survey Telescope for Astronomy,” but since it started in 2008 until now it could observe only in the infrared with VIRCAM. Moreover, with 4MOST the telescope will be able to obtain spectra, and not only images like VIRCAM, and a huge number of them (2400 spectra) in a single observation.
With VIRCAM, VISTA has had for these years the largest format infrared camera on a large telescope in the world. The recent move from infrared imaging to visible spectroscopy is a big change for VISTA, but infrared imaging continues and is now breaking new ground from space, where the European Euclid satellite is already delivery unique images with a sensitivity and resolution unavailable from the ground. So 4MOST ensures that VISTA will continue doing unique observations for many more years.”
Notes
[1] The dataset is too large to release as a single image, but the processed data and objects catalogue can be accessed in the ESO Science Portal.
[2] One way to measure the distance to a star is by comparing how bright it appears as seen from Earth to how intrinsically bright it is; but the latter is often unknown. Certain types of stars change their brightness periodically, and there is a very strong connection between how quickly they do this and how intrinsically luminous they are. Measuring these fluctuations allows astronomers to work out how luminous these stars are, and therefore how far away they lie.
[3] Vía Láctea is the Latin name for the Milky Way.
More information
This research was presented in a paper entitled “The VISTA Variables in the Vía Láctea eXtended (VVVX) ESO public survey: Completion of the observations and legacy” published in Astronomy & Astrophysics (https://doi.org/10.1051/0004-6361/202450584). Data DOI: VVV, VVVX.
Cover Image: This collage highlights a small selection of regions of the Milky Way imaged as part of the most detailed infrared map ever of our galaxy. Here we see, from left to right and top to bottom: NGC 3576, NGC 6357, Messier 17, NGC 6188, Messier 22 and NGC 3603. All of them are clouds of gas and dust where stars are forming, except Messier 22, which is a very dense group of old stars. The images were captured with ESO’s Visible and Infrared Survey Telescope for Astronomy (VISTA) and its infrared camera VIRCAM. The gigantic map to which these images belong contains 1.5 billion objects. The data were gathered over the course of 13 years as part of the VISTA Variables in the Vía Láctea (VVV) survey and its companion project, the VVV eXtended survey (VVVX). Credit: ESO
