Infrared Space Observatory Image of the Inner Galaxy at 7 micron wavelength
Credit: ESA/ISO, CAM, S. Ganesh, A. Omont and the ISOGAL Team.

The Milky Way's centre is the busy core of a metropolis, crowded with huge populations of stars frantically dancing to the rhythm of gravitation. These stars are precious for astronomers: they hold many clues to unveil the past and future history of our galaxy. But the galactic centre has remained a fairly unexplored place so far, due to the thick dust covering it. The European Space Agency's infrared space telescope, ISO, has crossed that dusty barrier and has observed the stellar populations at the galactic centre with a very high resolution during more than 255 hours. The results already show 100 000 stars never seen before. Further analysis of the data could confirm that the Milky Way swallowed neighbouring galaxies in the past.

The Milky Way is a large spiral galaxy 130 000 light-years across, which began to form about 10 000 or 15 000 million years ago - shortly after the origin of the Universe. It is structured in a thin disk with spiral arms and a great bulge in the centre, which as seen from the Earth lies towards the constellation of Sagittarius. Our Solar System is in the edge of one of the arms, about 25 000 light-years from the centre: a very quiet area compared to the inner central bulge.

This observation has been discussed in details in the ESA Information Note entitled: "ISO shows what's in the centre of our galaxy: 100 000 Stars seen for the first time".

The figure above is also available in high-resolution (300 dpi) format: Postscript gzipped

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