Find out in this animated video how Gaia carries out the Galactic Census of one billion stars.
Gaia will do even more than this – by repeating the measurements for five years, Gaia will also see all those one billion stars move. That is, we will know where the stars are now, and how they are moving through space. That extra information allows us to calculate stellar orbits, determine their place of origin, and crucially, weigh the Milky Way. Available measurements tell us that there is much more to our Galaxy than just the stars and gas – Gaia will also measure the Dark Matter, which holds the Milky Way together.
Figure on the right: Top panel: the parallactic ellipse, caused by the motion of the earth around the Sun. The size of the ellipse decreases linearly as distance increases. Second panel: The star’s “proper motion”, caused by its orbit in the Milky Way. Third panel: wobbles in the motion of a star caused by the gravitational pull on the star of its planets. Fourth panel: all effects combined, illustrating the motion which Gaia will measure.
Question: Gaia will measure the size, shape and distance of the stars in the Milky Way in a five-year cycle. What else do you think we can measure in the future? Share your thoughts using our Comments facility.
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