This composite image shows more than 84 million stars in the Milky Way galaxy. (European Southern Observatory )
Astronomers from the European Southern Observatory have released a striking new image of the Milky Way galaxy that shows more than 84 million stars, 10 times more than previous studies have provided. The zoomable image, constructed by computer-merging thousands of individual images, contains more than 9 billion pixels and would, if printed at the resolution of a typical book, measure 30 feet long and 23 feet tall.
The individual images used in the composite were obtained with the 4.1-meter (161-inch) Visible and Infrared Survey Telescope for Astronomy (VISTA) at ESO's Paranal Observatory in Chile. The survey was conducted at infrared wavelengths because visible light emanating from the stars near the center of the Milky Way galaxy is obscured by dust and gas surrounding the cluster of stars. VISTA is the largest telescope ever used to explore the central core of the Milky Way and it was used, in part, because that portion of the galaxy is visible only from the southern hemisphere. A team led by Chilean astronomers Roberto Saito and Dante Minniti reported their findings in the journal Astronomy & Astrophysics.
The team identified 173 million individual objects in the photo composite. Eighty-four million of them could be positively identified as stars; the remainder were more distant objects, such as other galaxies, or could not be unambiguously identified.
Using the data on which the image was based, the team was able to construct a diagram that charts the individual stars' brightness versus their colors. That allows the researchers to draw more information about the age and size of each star. The chart, for example, identifies red dwarf stars, which are thought to be valuable targets in the search for low-mass extrasolar planets. A separate study of the images, not yet completed, will search for pulsars, binary stars, starspots and other variable objects.