The Heidelberg Joint Astronomical Colloquium this 2023 summer semester takes place on Tuesdays at 16:00 at the large lecture hall (gHS), Philosophenweg 12. Anybody unable to attend the colloquium in person is invited to participate remotely using Zoom through the link: https://zoom.us/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 (Meeting ID: 942 0262 2849 Passcode: 792771). The colloquium is organised jointly by the Center for Astronomy at Heidelberg University (ZAH), the Max Planck Institute for Astronomy (MPIA), the Max Planck Institute for Nuclear Physics (MPIK), and the Heidelberg Institute for Theoretical Studies (HITS). For further information please contact Richard Tuffs (Richard.Tuffs@mpi-hd.mpg.de) or Ralf Klessen (klessen@uni-heidelberg.de).