Astronomers have followed 3I/ATLAS since its discovery on July 1. Hubble photographed it on July 21 from 277 million miles away, revealing a teardrop-shaped cloud of dust wrapped around its icy core.

Perihelion is the point at which an orbiting body is closest to the sun. The word comes from Greek and literally means around (peri) the sun (helios).

Somewhere in the orbit of Venus, scientists believe a hidden population of asteroids is circling the Sun—nearly invisible to Earth-bound telescopes and possibly capable of striking our planet with ...