Friday 3rd April 2020 7.30 pm, Michael Perryman (ESA/Gaia Project Scientist 1995 – 2008) Hipparcos and Gaia – Space Astrometry: unravelling the formation and evolution of our galaxy

The Hipparcos satellite project of the European Space Agency was dedicated to measuring the accurate positions of more than 100,000 stars. Doing so from space represented a fundamentally new discipline in space science. With the publication of the scientific results from the Hipparcos mission in 1997, ESA adopted the Gaia mission, a follow-on and vastly more advanced star-mapping satellite, in 2000. Gaia was launched in 2013 and continues to operate from its advantageous location at the Sun-Earth Lagrange point, L2. Gaia is measuring the positions of more than two billion stars in our Galaxy with extreme accuracy, and is set to revolutionise many areas of astronomy and astrophysics. The talk will explain why the measurement of star positions is of such scientific importance. It will review the two thousand year history of this branch of astronomy, called astrometry, explain why these measurements are being made from space, illustrate how the very exacting measurements are made in practice, and present some of the many areas of astronomy that are being impacted by these new experimental insights.