On October 30, the interstellar comet 3I/ATLAS is set to reach perihelion — its closest point to the Sun — at a distance of 1.35 astronomical units, or about 125 million miles (202 million kilometres). Perihelion marks the orbital point where an object is nearest to the Sun, a crucial phase for comets with highly eccentric orbits like 3I/ATLAS.

As comets draw closer to the Sun, rising temperatures cause the sublimation of surface ice, leading to outgassing and the formation of a bright coma around the nucleus. This activity also gives rise to two distinct tails: a dust tail and an ion tail, composed of charged particles swept away by solar wind. These processes peak during perihelion, significantly enhancing the comet’s brightness.

Unlike most comets in the solar system, 3I/ATLAS is not

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