Astronomers Discover Third Interstellar Comet: 3I/ATLAS

On July 1, 2025, astronomers utilizing the Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Río Hurtado, Chile, identified a new interstellar comet, designated 3I/ATLAS. This marks only the third known interstellar object to traverse our solar system, following the discoveries of 'Oumuamua in 2017 and 2I/Borisov in 2019.

The detection of 3I/ATLAS underscores the increasing capability of current astronomical surveys to identify objects originating from beyond our solar system. This discovery provides a unique opportunity to study material from other star systems, offering insights into the formation and evolution of planetary systems.

3I/ATLAS is traveling at approximately 37 miles per second (about 133,200 miles per hour) from the direction of the Milky Way's center. As of early August 2025, it is approximately 420 million miles from Earth, situated within Jupiter's orbit. The comet poses no threat to Earth, as its closest approach will be about 150 million miles away.

The comet exhibits a faint coma, indicating cometary activity. Estimates suggest its nucleus is between 10 and 30 kilometers in diameter. Observations from the Gemini North telescope in Hawaii have captured images revealing the comet's compact coma—a cloud of gas and dust surrounding its icy nucleus.

3I/ATLAS is expected to reach its closest approach to the Sun (perihelion) on October 29, 2025, at a distance of approximately 1.357 astronomical units (about 126 million miles). At perihelion, it will be moving at its maximum velocity of 68.3 kilometers per second (about 152,800 miles per hour) relative to the Sun.

Astronomers are conducting detailed observations using larger telescopes to study the comet's composition and trajectory. The Hubble Space Telescope captured images of 3I/ATLAS on July 21, 2025, and plans to perform ultraviolet spectroscopy in November 2025 to determine the composition of its gas emissions. The James Webb Space Telescope is scheduled to observe the comet in August and December 2025, aiming to detect compounds such as water, carbon monoxide, carbon dioxide, and ammonia.

The discovery of 3I/ATLAS provides a rare opportunity to study material from another star system, potentially offering insights into the formation of exoplanets and the early stages of planetary systems. Researchers are particularly interested in tracing the comet's origins and understanding more about our galaxy's planetary systems through its composition and behavior.

A recent, unreviewed research paper led by Harvard astronomer Avi Loeb suggests that 3I/ATLAS's high speed and unique trajectory might indicate an artificial origin, possibly as alien technology. However, this claim is widely refuted by experts, who emphasize that observations so far indicate typical cometary behavior.

The discovery of interstellar objects like 3I/ATLAS captivates public interest and underscores the dynamic nature of our solar system. It highlights the importance of global astronomical collaborations and the need for continued investment in space observation technologies. Additionally, such discoveries can inspire educational initiatives and public engagement in science.

The Asteroid Terrestrial-impact Last Alert System (ATLAS) is a global network of robotic telescopes designed to detect near-Earth objects that could pose a threat to our planet. Funded by NASA, ATLAS systematically surveys the night sky every 24 hours, identifying and tracking asteroids and comets. The system's ability to detect interstellar objects like 3I/ATLAS demonstrates its significant contribution to planetary defense and astronomical research.

The detection of 3I/ATLAS marks a significant milestone in the study of interstellar objects, offering a unique glimpse into the materials and processes of distant star systems. As astronomers continue to observe and analyze this comet, the data gathered will undoubtedly enrich our understanding of the cosmos and the myriad objects that traverse it.