Galaxy Story

The Galaxy in Which We Live

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Past, Present and Future of Our Galaxy

Many puzzles about our Milky Way remain to be solved.

Here are some examples:

Did the central bulge form before or after the disk? How many spiral arms does the Galaxy contain, what do they look like and what is their origin? What is the mysterious dark matter that affects the motions of stars in our Galaxy? When were stars in our Galaxy born? Did the Milky Way form by the collapse of a cloud of material or by accretion of smaller building blocks?

At present, we have accurate spatial and dynamical information for stars in a reduced area of the Galaxy, around the Sun. This has been achieved with the data gathered by the Hipparcos satellite, launched by ESA in 1989. But clearly, conclusions about the large-scale structure and dynamics of our Milky Way need a much deeper and more extensive survey.

Gaia, a satellite that the European Space Agency will launch about 2011, will finally be able to solve these questions. For more information about Gaia and its planned mission, click the Gaia website link below.

Click on the Thumbnail below to see how Gaia will greatly increase our knowledge about the Milky Way:

Measuring the Milky Way


ESA Science Home page