White paper for the Voyage 2050 long-term plan in the ESA Science Programme Faint objects in motion: the new frontier of high precision astrometry Contact Scientist: Fabien Malbet Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) Université Grenoble Alpes, CS 40700, F-38058 Grenoble cedex 9, France Email:
[email protected], Phone: +33 476 63 58 33 version 20190805 Faint objects in motion : the new frontier of high precision astrometry Faint objects in motion: the new on the most critical questions of cosmology, astron- frontier of high precision astrometry omy and particle physics. Sky survey telescopes and powerful targeted telesco- 1.1 Dark matter pes play complementary roles in astronomy. In order to The current hypothesis of cold dark matter (CDM) ur- investigate the nature and characteristics of the mo- gently needs verification. Dark matter (DM) is essential tions of very faint objects, a flexibly-pointed instrument to the L + CDM cosmological model (LCDM), which suc- capable of high astrometric accuracy is an ideal comple- cessfully describes the large-scale distribution of galax- ment to current astrometric surveys and a unique tool for ies and the angular fluctuations of the Cosmic Microwave precision astrophysics. Such a space-based mission Background, as confirmed by the ESA / Planck mission. will push the frontier of precision astrometry from ev- Dark matter is the dominant form of matter (∼ 85%) in idence of earth-massed habitable worlds around the the Universe, and ensures the formation and stability of nearest starts, and also into distant Milky way objects enmeshed galaxies and clusters of galaxies.