In ancient times, and until about a century ago, astronomers were essentially astrometrists, measuring the effemerides of the stars. It had also several practical applications, such as calendars, navigation, and agriculture. Since the beginning of the human history, measuring the positions of the celestial objects was of fundamental importance to understand the structure of the visible sky. The description of the celestial sphere is probably one of the oldest fields of scientific investigation. We summarize the future directions in space astrometry that are proposed or under investigation by the scientific community, their main challenges and the expected outcome.Īstrometry is concerned with the measurements of the positions and motions of celestial objects, going from planets and other Solar system objects, through stars within our Galaxy, to, at least in principle, to galaxies and clusters of galaxies within the Universe. While both options have the potential to bring us in a new era of discovery, they have to face enormous issues.
The next big advance in space astrometry would be either to improve the astrometric accuracy of one order of magnitude, or to move to a different wavelength domain. We briefly outline the properties of Gaia first and second data release, and the accuracies expected end-of-mission. ESA space missions Hipparcos first and then Gaia point out the outstanding contribution that space astrometry can provide to our knowledge in many fields of astrophysics, going from the Milky Way formation and evolution, to stellar astrophysics, extra-galactic astrophysics, and fundamental physics. Nowadays a major breakthrough is on the way due to astrometric sky surveys from space. Over the centuries astrometry has greatly contributed to the advance of the knowledge of the Universe. This contribution focuses on the importance of astrometry and on its future developments.
Astronomical Observatory of Padova, National Institute for Astrophysics (INAF), Padova, Italy.
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