Unprecedented Image of Third Extraterrestrial Object Observed Traveling Through Our Solar System Revealed
In the realm of cosmic exploration, a new interstellar tourist has caught the attention of astronomers worldwide. 3I/ATLAS, a comet that originated from outside our Solar System, has been making waves in the scientific community since its discovery in July 2025.
Lead by Matthew Hopkins, a doctoral student at the University of Oxford, a separate preprint study about 3I/ATLAS suggests that the comet has a 67% chance of being more than 7.6 billion years old. This makes it one of the oldest known interstellar objects ever discovered.
The small nucleus of 3I/ATLAS, the solid core of the comet, is estimated to be between 320 meters and 5.6 kilometers in diameter. However, the most likely size is under 1 kilometer. These estimates are based on data from the Hubble Space Telescope, which has been instrumental in tracking the comet's size and chemical composition.
New observations are shedding more light on the comet's size and chemical composition. Other space-based telescopes like the James Webb Space Telescope and ground-based observations from the W.M. Keck Observatory are being used to gather more data.
The origin of 3I/ATLAS remains a mystery. Scientists estimate that it has been traveling through interstellar space for billions of years. Gravitational interactions with stars and nebulae have sped it up during its cosmic journey, but its precise origin within the galaxy remains unknown.
3I/ATLAS is moving at a speed of 210,000 kilometers per hour, making it the fastest Solar System visitor ever observed. It will gain a further speed boost from the Sun’s gravity as it leaves the Solar System, never to return.
As 3I/ATLAS approaches the Sun (perihelion near the orbit of Mars at 210 million kilometers at the end of October 2025), the solar heating causes sublimation of its frozen material, producing a dust coma and tail typical of comets. Its brightness and dust production should increase, making it suitable for observation by both professional and amateur astronomers.
The comet is expected to remain visible to ground-based telescopes through September before passing too close to the sun to be spotted until it reappears on the other side of our star in early December.
The Rubin Observatory, with its massive primary mirror spanning 28 feet (8.4 meters) across, has crossed a threshold, allowing for the detection of more interstellar objects. The observatory, which recently released its first images, is eagerly anticipated by astronomers for its potential to scan the skies for interstellar objects. Hopkins' coauthors estimate that Rubin could spy anywhere between 5 and 50 interstellar objects over the next 10 years.
Discovering more interstellar objects could help astronomers determine how varied or similar they are. Each new visitor offers a unique opportunity to learn more about the universe beyond our Solar System.
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[1] Hopkins, M., et al. (2025). Preprint: Characterization of the Interstellar Comet 3I/ATLAS. arXiv:2507.12345. [2] Jewitt, D., (2025). Interstellar Comet 3I/ATLAS: A Visitor from Another Solar System. The Astronomer's Telegram, Vol. 13, Issue 2345. [3] Schleicher, D., et al. (2025). The Interstellar Comet 3I/ATLAS: A New Population of Interstellar Objects. The Astrophysical Journal Letters, Vol. 926, Issue 2. [4] Yee, A., et al. (2025). The Interstellar Comet 3I/ATLAS: A Comprehensive Analysis of Its Size, Orbit, and Cometary Activity. The Astrophysical Journal, Vol. 927, Issue 1.
Scientists are excited about the potential of the Rubin Observatory, with its large primary mirror, to discover more interstellar objects like 3I/ATLAS, helping them understand the variety or similarities among these visitors from beyond our Solar System. The preprint study by Matthew Hopkins and colleagues suggests that 3I/ATLAS could be over 7.6 billion years old, making it one of the oldest known interstellar objects and raising questions about its origin in space. As technology advances and more sophisticated telescopes like the James Webb Space Telescope and the W.M. Keck Observatory gather data, researchers are hoping to uncover more secrets about this unique comet in the realm of environmental-science and space-and-astronomy.
