25 October 2012

84 million stars captured in biggest Milky Way catalogue

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The European Southern Observatory’s VISTA telescope has created the largest catalogue of our galaxy, in a nine gigapixel, zoomable, colour image of more than 84 million stars – 10 times more than any previous studies.
ESO VISTA image Milky Way 84 million stars

SYDNEY: The European Southern Observatory’s VISTA telescope has created the largest catalogue of our galaxy, in a nine gigapixel, zoomable, colour image of more than 84 million stars – 10 times more than any previous studies.

The Milky Way image is one of the biggest astronomical images ever produced. It is so large that, printed at the resolution of a “typical book” it would be nine metres long by seven metres tall, according to a statement released by the ESO.

The team of international astronomers behind the study focussed on a concentrated cluster of ancient stars surrounding the Milky Way’s centre, called the ‘bulge’, which is a characteristic of most spiral galaxies and key to understanding their formation.

“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,” said lead author of the study Roberto Saito, from Pontificia Universidad Católica de Chile, in a statement.

Star census

The ESO’s 4.1-metre VISTA (Visible and Infrared Survey Telescope for Astronomy) telescope in Cerro Paranal, Chile, uses a large mirror, wide field of view and ultra-sensitive infrared detectors which make it possible to see past the dust clouds obscuring the stars at the Milky Way’s centre.

Using data from the enormous colour image, astronomers can study different properties of the 84 million stars, including their temperature, 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,” explained study co-author Dante Minniti, also from Pontificia Universidad Católica de Chile.

Prime candidates for exoplanets

One noteworthy find already made from the image is the large number of red dwarf stars in this part of our galaxy – prime candidates around which to search for exoplanets.

“So it’s a whole new catalogue or collection of stars that we can now look for planets,” commented Amanda Bauer, an expert in galaxies and galaxy formation at the Australian Astronomical Observatory, who was not involved in the study. Exoplanets would be searched for using the ‘transiting method’ – looking for a planet temporarily blocking light from its star.

Bauer also said that being able to determine the age of the stars at the galaxy’s centre would be of vital importance to our understanding of the formation of galaxies in the distant universe.

“Figuring out how old stars are in the centre of the galaxy is a critical thing that we can’t look at in the distant universe, so to be able to understand that in our own galaxy – how these stars got into the centre – is just a fascinating prospect,” she said. “I’m really looking forward to seeing what some of the analyses determine from these stars.”

The ESO will make all the data publically available through its data archive. “So we expect many other exciting results to come out of this great resource,” Saito added.

With the European Southern Observatory
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