Pre-discovery Activity of New Interstellar Comet 2I/Borisov beyond 5 au
Pre-discovery Activity of New Interstellar Comet 2I/Borisov beyond 5 au
Comet 2I/Borisov, the first unambiguous interstellar comet ever found, was discovered in August 2019 at $\sim3$ au from the Sun on its inbound leg. No pre-discovery detection beyond 3 au has yet been reported, mostly due to the comet's proximity to the Sun as seen from the Earth. Here we …