NASA Confirms Third Interstellar Object, 3I/ATLAS, Passing Through Solar System

NASA has confirmed the discovery of 3I/ATLAS, marking it as the third known interstellar object to pass through our solar system. Initially detected in late June by the Asteroid Terrestrial-impact Last Alert System (ATLAS), the object was first cataloged as A11pl3Z. Subsequent analysis by NASA and the International Astronomical Union (IAU) reclassified it as interstellar, leading to its formal designation as 3I/ATLAS.

Traveling at approximately 60 kilometers per second, 3I/ATLAS is approaching from the direction of the constellation Sagittarius. Its hyperbolic trajectory indicates that it is not gravitationally bound to the Sun, suggesting a one-time passage through our solar system. As of early July, the object was about 416 million miles from the Sun. It is projected to reach its closest approach to the Sun, or perihelion, on October 30, passing just inside the orbit of Mars at 1.4 astronomical units (AU) from the Sun. The object will maintain a safe distance from Earth, with a minimum approach of 1.6 AU, or approximately 240 million kilometers.

Initial observations suggested that 3I/ATLAS resembled an asteroid, akin to the 2017 interstellar visitor 'Oumuamua. However, recent imagery and spectroscopic data from the IAU's Minor Planet Center reveal signs of cometary activity, including a faint coma and a short tail. This led to its full designation as C/2025 N1 (ATLAS). Professor Colin Snodgrass, a planetary astronomer at the University of Edinburgh, noted that the presence of a small comet-like tail implies that much of the object's brightness is due to the coma, suggesting that the solid nucleus may be smaller than initially estimated.

Astronomers are preparing for limited observation windows due to the object's current location and low brightness. As 3I/ATLAS approaches, it is expected to brighten, potentially becoming visible to amateur astronomers. NASA has indicated that the comet will be obscured by the Sun's glare by late September, temporarily limiting observations. It will reappear in December as it exits the solar system, offering a final opportunity for data collection. Scientists are planning observations using the Vera C. Rubin Observatory, the James Webb Space Telescope, and Mars-based rovers, which may capture images as the comet passes near the Red Planet.

While only three interstellar objects have been confirmed to date, scientists suspect that many more may pass through our solar system undetected. A 2022 study published in The Astrophysical Journal Letters estimated that as many as one interstellar object per year could traverse the inner solar system, most of them too small or faint to detect with current instruments. Dr. Mark Norris, senior lecturer in astronomy at the University of Central Lancashire, stated that the discovery of 3I/ATLAS provides additional evidence that such interstellar wanderers are relatively common in our galaxy.