Colloquium: The GaiaNIR mission and the hidden regions of our Galaxy
Our Galaxy contains many different types of stars and planets, interstellar gas and dust, and dark matter. These components are widely distributed in age, reflecting their formation history, and in space, reflecting their birth place and subsequent motion. Objects in the Galaxy move in a variety of orbits that are determined by the gravitational force, and have complex distributions of different stellar types, reflecting star formation and gas-accretion history. Understanding all these aspects in one coherent picture is being partially achieved by the Gaia mission, which surveyed around 1% of the Galaxy. The Gaia mission focused on astrometry which makes precise angular measurements of stellar positions, parallaxes/distances and proper motions on the sky. The field dates back to antiquity with the work of Hipparchus (190-120 BC) and Ptolemy (100-170 AD).
Despite these significant advancements, much more can be achieved by harnessing Near InfraRed (NIR) light using new state-of-the-art detectors to peer through the dust and gas to reveal the hidden regions of the Galaxy. A new all-sky NIR astrometric mission will expand and improve on the science of Gaia using basic astrometry. NIR astrometry is crucial for penetrating obscured regions and for observing intrinsically red objects that are otherwise difficult to detect. The new mission is aimed at surveying at least 15 billion stars in the Galaxy, revealing important new regions obscured by interstellar gas and dust while also significantly improving on the accuracy of the previous results from Gaia. The new mission would not launch until around 2045-2050 but work on developing the concept has already begun. This mission promises to revolutionise our understanding of the dynamics of our Galaxy, offering new insights into its hidden ecosystems and to reveal nature's true complexity and beauty in action.