Milky Way Galaxy 9-Gigapixel Image Shows 84 Million Stars

An incredible 9-megapixel image of the Milky Way has been created with images taken by the VISTA infrared survey telescope at ESO’s Paranal Observatory. The new image is essentially a catalogue of more than 84 million stars located in the central parts of the Milky Way.


This enormous dataset is an impressive leap over previous similar studies, containing more than ten times the stars of previous work. The researchers think that this work should go a long way in helping to further understand our galaxy.

The image allows those viewing it to zoom in to the central parts of the Milky Way to an incredible degree. It’s such a large image that if you “printed with the resolution of a typical book, it would be 9 metres long and 7 metres tall.”

“By observing in detail the myriads of stars surrounding the centre of the Milky Way we can learn a lot more about the formation and evolution of not only our galaxy, but also spiral galaxies in general,” explains Roberto Saito (Pontificia Universidad Catolica de Chile, Universidad de Valparaiso and The Milky Way Millennium Nucleus, Chile), lead author of the study.

The majority of spiral galaxies, including the Milky Way, possess an enormous concentration of truly ancient stars around the center, referred to as the bulge. Knowing more about how this formed is considered by researchers to be vital to understanding the galaxy as a whole. Looking into this incredibly dense, turbulent region is not easy though.

“Observations of the bulge of the Milky Way are very hard because it is obscured by dust,” says Dante Minniti (Pontificia Universidad Catolica de Chile, Chile), co-author of the study. “To peer into the heart of the galaxy, we need to observe in infrared light, which is less affected by the dust.”


“The large mirror, wide field of view and very sensitive infrared detectors of ESO’s 4.1-metre Visible and Infrared Survey Telescope for Astronomy (VISTA) make it by far the best tool for this job. The team of astronomers is using data from the VISTA Variables in the Via Lactea programme, one of six public surveys carried out with VISTA. The data have been used to create a monumental 108 200 by 81 500 pixel colour image containing nearly nine billion pixels. This is one of the biggest astronomical images ever produced. The team has now used these data to compile the largest catalogue of the central concentration of stars in the Milky Way ever created.”

In order to analyze this catalogue “the brightness of each star is plotted against its colour for about 84 million stars to create a colour-magnitude diagram. This plot contains more than ten times more stars than any previous study and it is the first time that this has been done for the entire bulge. Colour-magnitude diagrams are very valuable tools that are often used by astronomers to study the different physical properties of stars such as their temperatures, masses and ages.”

“Each star occupies a particular spot in this diagram at any moment during its lifetime. Where it falls depends on how bright it is and how hot it is. Since the new data gives us a snapshot of all the stars in one go, we can now make a census of all the stars in this part of the Milky Way,” explains Dante Minniti.

This new image, a colour-magnitude diagram of the bulge, will be a very useful tool for any research into this region. An interesting discovery has already been made with it, the large numbers of faint red dwarf stars. These stars are considered to be prime candidates for the search for possible exoplanets using the ‘transit method’.

“One of the other great things about the VVV survey is that it’s one of the ESO VISTA public surveys. This means that we’re making all the data publicly available through the ESO data archive, so we expect many other exciting results to come out of this great resource,” concludes Roberto Saito.

Source: European Southern Observatory – ESO

Image Credits: ESO/VVV Consortium/Nick Risinger, Ignacio Toledo, Martin Kornmesser

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