Interstellar comet 3I/ATLAS has experienced a significant increase in brightness as it approaches perihelion, the point in its orbit closest to the sun, on October 30. This unique object, which is the third interstellar comet ever discovered, was first identified on July 1, 2025, and is believed to have originated from outside our Solar System.
After passing just inside the orbit of Mars, the comet could not be observed from Earth. However, astronomers from the European Space Agency (ESA) have utilized ground-based telescopes in locations such as Hawaii, Chile, and Australia to track its trajectory. Observations have also been made by several space telescopes, including the NASA/ESA Hubble Space Telescope and the NASA/ESA/CSA James Webb Space Telescope. Other satellites monitoring the comet include the National Oceanic and Atmospheric Administration”s GOES-19 weather satellite and NASA“s Polarimeter to Unify the Corona Heliosphere (PUNCH) mission, along with the Solar and Heliospheric Observatory (SOHO) from NASA and ESA, according to reports from Universe Today.
Despite some speculation regarding the possibility of comet 3I/ATLAS being an alien spacecraft, most astronomers assert that it is a natural space rock from an unknown star system. A study released on October 28 on the preprint server arXiv indicated that the comet exhibited rapid brightening as it neared perihelion. The research team estimates that the comet will reach a brightness of approximately magnitude 9 at perihelion, making it visible with high-quality backyard telescopes, although still too faint for unaided human eyes.
The study utilized data from space-based solar instruments such as GOES-19 and SOHO, revealing that the comet is “distinctly bluer than the sun.” This observation aligns with the understanding that gases emitted from the comet contribute significantly to its brightness as it approaches the sun. As comets get closer to the sun, their surface ices sublimate into gases, forming a surrounding envelope that enhances their visibility. Solar radiation then ionizes these gases, further increasing brightness.
What sets comet 3I/ATLAS apart is its extraordinary speed, exceeding 130,000 mph (210,000 km/h), and its straight, flat trajectory through our solar system. Earlier statements from NASA indicate that 3I/ATLAS is traveling at the highest velocity recorded for any solar system visitor. This rapid movement suggests that the comet has been drifting through interstellar space for billions of years, with its speed increasing over time. Some experts believe that 3I/ATLAS could be the oldest comet observed, potentially around 3 billion years older than our Solar System, which is estimated to be 4.6 billion years old.
Additionally, this comet may be the largest interstellar object seen to date, although researchers are still refining measurements of its size. Data from the Hubble Space Telescope suggests that 3I/ATLAS could have a maximum width of about 3.5 miles (5.6 km).
According to NASA, the comet is expected to be visible again to Earth-based telescopes by early December. It may also be observable by spacecraft orbiting Jupiter as it approaches the gas giant in March 2026.
