Washington: Scientists have produced a detailed three-dimensional map of the stars that form the inner regions of our Milky Way galaxy.
They found a box/peanut shaped bulge with an elongated bar and a prominent X-structure, which had been hinted at in previous studies.
This indicates that the Milky Way was originally a pure disk of stars, which then formed a thin bar, before buckling into the box/peanut shape seen today.
By using a large number of so-called "red clump" giant stars from the new VVV survey scientists at the Max Planck Institute for Extraterrestrial Physics produced the 3-dimensional map of the galactic bulge.
The scientists used the VVV near-infrared survey of the bulge conducted with the VISTA telescope in Chile, which covers the inner regions of the Milky Way and is able to observe stars thirty times fainter than previous bulge surveys.
The observations were carried out by the VVV team, who then made their images and star catalogues available to the international community as science data products in the European Southern Observatory science archive facility.
Red clump giant stars were chosen for this study as they can be used as a standard candle: at this stage in the star`s lifetime their luminosity is approximately independent of their age or composition.
The amount of gas and dust obscuring the stars is calculated directly from the observed colours of the red clump stars, so that their brightness distribution without obscuration can be measured.
Because red clump stars have nearly the same intrinsic brightness, this gives approximate distances to each star.
The good spatial coverage of the VVV survey allowed measurements across the whole inner region of the Milky Way, and from these the three-dimensional measurement of the structure of the bulge was constructed.
Photo: European Southern Observatory