Relative positions of 2I/Borisov and other solar system bodies during the VLT/MUSE observing campaign, shown in International Celestial Reference Frame coordinates at the scale of astronomical units (au). The trajectory of 2I follows the dashed line in the direction of the arrows. Green circles indicate the positions of 2I and Earth at each of the 16 observing epochs (Table 1). Colored symbols are additional events identified independent of our data: yellow diamonds represent 2I and Earth’s positions at discovery on 2019 August 30, orange triangles the outburst of 2020 March 4–9 (M. Drahus et al. 2020), and blue squares when the fragment was resolved by HST on 2020 March 30 (D. Jewitt et al. 2020). The black lines outward from the Sun (yellow circle) are the orbits of Mercury, Venus, Earth, and Mars.