Colloquium on Jan. 8, 2026

Synergistic Detection of Dark Objects with Gaia Astrometry

Speaker: Fabo Feng (SJTU)

Venue: SWIFAR Building 2111

Time: 16:00 PM, Thursday, Jan. 8, 2026

Abstract:

Gaia, the most precise astrometric survey to date, is transforming our understanding of dark objects in the Galaxy. By combining Gaia and Hipparcos astrometry, hundreds of exoplanets and substellar companions have been detected and confirmed. Their absolute mass measurements reveal a brown dwarf desert extending to ≈20 au, likely marking the transition between planetary and stellar formation pathways, while the three-dimensional orbits of giant companions in hot- and warm-Jupiter systems indicate that at least one third undergo Kozai–Lidov oscillations. Beyond planets, Gaia astrometry enables the detection of stellar-mass black holes, providing key constraints on their mass function and formation. Moreover, reprocessing Gaia astrometric data with gravitational-wave models will enable the detection of low-frequency gravitational waves with sensitivity comparable to pulsar timing arrays, potentially leading to the first detection of a nearby supermassive black hole binary. The upcoming Gaia DR4 (expected by the end of 2026) will significantly enhance astrometric precision and time coverage, further advancing studies of exoplanets, dark companions, black holes, and gravitational waves.