April saw the release of the Detailed Science Case for MSE, 2019 edition, the culmination of many months (and in some cases, years) of effort by 263 scientists across the MSE community. This new document is a comprehensive revision of the original DSC, first released in 2016, and captures the key science ambitions of the MSE community for this transformational facility.

As described in the DSC, major pillars in the science program for MSE include (i) the ultimate Gaia follow-up facility for understanding the chemistry and dynamics of the distant Milky Way, including the outer disk and faint stellar halo at high spectral resolution (ii) galaxy formation and evolution at cosmic noon, via the type of revolutionary surveys that have occurred in the nearby Universe, but now conducted at the peak of the star formation history of the Universe (iii) derivation of the mass of the neutrino and insights into inflationary physics through a cosmological redshift survey that probes a large volume of the Universe with a high galaxy density.

Special thanks go out to the various science working groups who worked on developing the science cases presented in each chapter, especially the co-leads of each group who organized the effort. These include Maria Bergemann & Daniel Huber (Exoplanets and stellar astrophysics), Sivarani Thirupathi & David Yong (Chemical nucleosynthesis), Carine Babusiaux & Sarah Martell (The Milky Way and resolved stellar populations), Manoj Kaplinghat & Ting Li (Astrophysical tests of dark matter), Aaron Robotham & Kim-Vy Tran (Galaxy formation and evolution), Sara Ellison & Yue Shen (Active Galactic Nuclei and supermassive black holes), Will Percival & Christophe Yeche (Cosmology), Adam Burgasser & Daryl Haggard (Time domain astronomy and the transient Universe).

Project Scientist Jennifer Marshall was effusive in her praise of the science team . “Its tremendously exciting to see the science of MSE presented so clearly and comprehensively”, said Jennifer. “The team have done a fantastic job. Whether its exoplanets or neutrinos, the Milky Way galaxy or high redshift quasars, MSE really is poised to transform our understanding across all fields of astronomy. We can’t wait to get this facility on sky to start making these science goals a reality”.