S348: 21st Century Astrometry – Crossing the Dark & Habitable Frontiers

The Gaia mission is designed for astrometry, but is also outlining dark matter and identifying exoplanets (ESA)

Understanding the nature of dark matter and finding habitable exoplanets in nearby star systems will transform modern science and have far-reaching consequences. Because dark matter and exoplanets are expected to leave an imprint on the kinematical and dynamical properties of normal matter, astrometry promises to be among the most exquisite techniques to probe their existence. The IAU Symposium 348 is a first step toward joining different communities and fostering bridges to enable such fundamental questions to be answered from astrometric measurements.

Astrometry is currently facing new challenges and crossing new frontiers thanks to increased levels of precision and accuracy. Building on the Gaia mission’s success, new missions are proposed to do further space-based astrometry (e.g., nano-JASMINE, Theia, GaiaNIR, LEGOLAS, AGP). There are also plans to build on astrometry results using non-astrometric missions and ground-instruments (e.g., HST, Euclid, JWST, WFIRST, GRAVITY on VLTI, MICADO on ELT, VERA). Together, these facilities are expected to bring the faint Universe to our fingertips.

The detection of ultra-faint dwarf galaxies and micro-arcsecond per year level measurements of their internal kinematics will be ground-breaking for dark matter. Precision next-generation astrometric facilities are expected to probe the very nature of this elusive component of our Universe. Also, in the near future, Gaia will reveal thousands of Jupiter-like exoplanets, and future missions (aiming at sub-micro-arcsecond performance) will enable census and system characterization of Earth-mass planets within the nearest FGK stars’ habitable-zones, paving the way for exobiology missions. Finally, these measurements will also empower studies of gravity, inflation, matter’s behaviour within nature’s most extreme environments and the determination of the Hubble constant to unprecedented accuracy.

During S348, we will witness keynote contributions on all such subjects. We will hear about how modern astrometry has been impacting dark matter studies using dwarf galaxies’ internal and global kinematics, as well as the Milky Way’s kinematics, as laboratories, and how the Milky Way itself is structured and evolving through cosmic time.

We will also learn how novel studies promise to probe different regimes of gravitational field strengths, ranging from Black Holes to gravitationally lensed and multiply imaged quasars (which can also give us the Hubble constant) to wide binary stars. Since astrometry provides fundamental measurements used to study the densest regimes of matter, we will hear about constraining the equation of state of compact objects and providing information about white dwarfs and pulsars.

One S348 session is dedicated to the fundamental step of measuring cosmological distances in the Universe, and will include results of the calibration of different standard rulers to derive the Hubble constant from the construction of cosmic distance ladders.

In another session, we will learn how astrometry is fundamental to the study of extrasolar planets, and how dynamic studies of multi-planet systems are dependent on astrometric measurements. Exciting prospectives considering the recent and forthcoming data from Gaia and other space missions will be presented and discussed, with a special focus on the detection and characterisation of rocky planets similar to Earth at Habitable Zone distances from their parent stars.

Finally, hypervelocity stars are important probes of the gravitational potential of the Milky Way, and we will see how they are being looked for and how they are being used to study the potential of the Milky Way.

The above studies depend on the use and development of sophisticated statistical and analytical tools, and information technology. Recognizing this, S348 will dedicate a session to a review and discussion about how modern methods, such as Bayesian analysis, Machine Learning, Information Field Theory, and modern computational databases, are being used to enable astrometry to tackle all these challenging scientific problems.

The science program of S348 will also keep an eye on exciting new space mission concepts. These concepts are driving astrometry towards new questions without neglecting its long-standing fundamental place in defining the reference frame used in astronomy and beyond — an issue to be discussed during the IAU Division A: Fundamental Astronomy meeting on 27 August.

Inheriting from astrometry’s past, remaining anchored to its promising and fulfilling present, yet with a sharp eye towards its exciting future, S348 will lay down paths for us to address together some of the most profound questions of modern science.

ALBERTO KRONE-MARTINS is an astronomer at the Universidade de Lisboa working with Gaia, Signal Processing, Statistics, and Machine Learning pushing Astrometry toward new horizons as Gravitational Lensing.


CÉLINE BOEHM is the director of the Physics School of the University of Sydney and a Professor from University Durham, a well-known Dark Matter specialist, and proponent of viable Dark Matter candidate particles.


ALESSANDRO SOZZETTI is a senior astronomer at Istituto Nazionale di Astrofisica (INAF) – Turin Observatory where he pushes exoplanet studies and discoveries with the responsibility of organizing the exoplanet processing of the Gaia mission.


ALAIN LEGER is a distinguished astronomer from IAS France, who first identified the “unidentified” IR emission in interstellar dust, and helped creating the DARWIN, Corot, NEAT and Theia mission concepts.