Telescope images show growing tail on interstellar comet 3I-Atlas
Gemini South observations reveal a widening coma and an extending tail as the visitor from another star approaches perihelion
Astronomers say new telescope images show a growing tail on a comet that originated beyond the solar system, confirming the object is becoming more active as it speeds toward the sun.
The most detailed pictures yet of the interstellar visitor, taken late last month by the Gemini South telescope in Chile and released Thursday by NSF’s NOIRLab, show a wide coma of dust and gas surrounding an icy nucleus and a tail that is noticeably more extended than in earlier observations. NOIRLab said the images indicate increased activity as the comet heats while moving inward through the solar system.
Designated 3I-Atlas, the comet is the third confirmed interstellar object detected passing through the solar system. As of Thursday, NASA listed the object at about 238 million miles (384 million kilometers) from Earth. It is expected to reach its closest point to the sun, or perihelion, at the end of October and to make its nearest approach to Earth in December at roughly 167 million miles (269 million kilometers) away, a distance greater than that between Earth and the sun.
The first two known interstellar objects were 1I/‘Oumuamua, discovered in 2017, and 2I/Borisov, discovered in 2019. Like those visitors, 3I-Atlas offers researchers a rare chance to study material formed around another star. Early observations of 3I-Atlas have focused on its coma and tail, which are produced as sunlight warms volatile ices and releases gas and dust.
Gemini South’s images, captured with powerful optical instrumentation, provide a clearer view of the comet’s structure and activity than earlier, lower-resolution shots. Astronomers said the photographs reveal both dust and gas components in the coma and show the tail extending farther from the nucleus than in prior images, consistent with increased sublimation of ices as solar heating intensifies.
NASA and ground-based observatories are tracking 3I-Atlas as it moves through the inner solar system. Scientists emphasized that the object poses no threat to Earth; its projected paths place it well outside Earth-crossing trajectories. Observations in the coming weeks and months are expected to refine measurements of the comet’s composition, activity levels and trajectory.
The arrival of 3I-Atlas continues to draw attention from astronomers who study small bodies and interstellar material. Each interstellar visitor has exhibited different characteristics: ‘Oumuamua showed an unusual elongated shape and non-gravitational accelerations, while Borisov displayed a more typical cometary appearance with clear cometary emissions. 3I-Atlas joins that small but scientifically important class of objects, and ongoing monitoring aims to place its properties in context with previously observed interstellar interlopers.
Data from Gemini South and other observatories will feed into models used to understand how objects formed around other stars compare with those in the solar system, and to track changes in 3I-Atlas as it reaches and passes perihelion. Scientists say coordinated observations across wavelengths will help determine the proportions of dust, ices and gas being released and how that activity evolves as the comet recedes from the sun after its closest approach.