In the twinkling holiday markets and bonhomie of Midtown’s pedicab Santas, there is something of the summer of 2020 — when we picnicked in Central Park but knew we’d be missing friends come fall.

New full-color images of interstellar comet 3I/ATLAS capture a rare visitor in vivid detail just days before it makes its closest pass by Earth, revealing a shifting palette of reds and greens that ...