Lightcurves of asteroids: spin, 3-D shape, density

International audienceThe study of the physical properties of asteroids, spin and 3-D shape, is the first step in understanding their formation and the mechanisms that dictate their evolution. The 3-D shape is indeed required to compute precisely the density, the only quantity that tells us about the internal structure from remote sensing, which is at the crux of the question of the location of formation. Bodies accreted far from the Sun contain volatiles elements (ices) and are less dense. Similarly, the spin orientation is key in triggering the orbital Yarkovsky drift effect, which ultimately delivers meteorites to the Earth. Observations by amateur astronomers and professional astronomers are complementary to study these properties. Lightcurves provided by amateurs combined with high-angular resolution images obtained by professionals with 8m class telescopes allow detailed modeling of asteroids. In this proceeding, we describe the motivations to study asteroid physical properties, describe several on-going professional-amateur observing campaigns, and illustrate then with a few results