On October 30, 2025, an astronomical event awaits as comet 3I/ATLAS reaches its closest approach to the Sun, known as perihelion. This event places the comet a mere 1.35 Astronomical Units away from our star, approximately 202 million kilometers. At this proximity, the intensity of solar heat leads to the sublimation of the comet’s icy components, igniting activity within its coma and generating two distinct tails—one of dust and another of ions.
Why is it invisible from Earth?
Strikingly, despite its peak activity, 3I/ATLAS is currently hidden from Earth’s view. This situation arises from its alignment with the Sun, having entered solar conjunction at the end of September. In layman’s terms, the comet has maneuvered behind the Sun from our perspective, becoming lost in the immense glare of our star.
As a result, ground-based telescopes and even those orbiting Earth are unable to conduct observations during the perihelion phase. The comet is not expected to reappear in the morning sky until late November or early December. By then, its anticipated brightness will enable astronomers and astrophotographers to capture this fleeting spectacle, with instruments like the Hubble Space Telescope and the James Webb Space Telescope ready to uncover its mysteries.
Space missions stepping up
In a bid to avoid losing out on the opportunity to study 3I/ATLAS during its most vibrant phase, several space missions stationed at different points within the solar system have taken on the task of tracking this celestial wanderer. Notably, Martian missions are proving particularly valuable; orbiters around the Red Planet have a clear line of sight regarding the solar hemisphere where 3I/ATLAS resides. This positioning allows them to observe the comet away from the Sun’s glare.
Among other missions that have found their gaze fixed on 3I/ATLAS are the Psyche spacecraft, en route to the asteroid of the same name, and Lucy, which aims for Jupiter’s Trojan asteroids. Both spacecraft have positioned themselves advantageously to collect data on this interstellar comet. The JUICE mission, designed to explore Jupiter’s icy moons, is also in the general vicinity of the comet. Despite this, there’s a delay in data transmission, since the mission employs its main antenna as a shield against solar radiation, meaning comprehensive findings won’t debut until February of the following year.
The scientific intrigue surrounding perihelion
At perihelion, the focus turns to understanding the chemical makeup of 3I/ATLAS. Scientists are particularly keen to analyze the gases and dust released during this phase, as these emissions provide insights into the comet’s origin. Previous observations have already highlighted that 3I/ATLAS contains higher levels of carbon dioxide and nickel compared to comets born within our solar system.
Such distinctions are not merely academic; they hold pivotal implications. The composition of 3I/ATLAS serves as a time capsule, reflecting the chemistry of its molecular cloud from which it was born over seven billion years ago. This allows for direct comparisons with the biochemical evolution of our own solar system.
As the world waits for this stellar encounter, questions linger. What more will we discover about 3I/ATLAS as it unveils its secrets in the night sky? The next few years promise to be an exciting chapter for astronomy enthusiasts and scientists eager to unlock the mysteries woven into this celestial traveler’s path.
