In a groundbreaking discovery, NASA has confirmed the arrival of a massive interstellar object, officially named 3I/ATLAS, hurtling through our solar system at an extremely high velocity.
The fast-mover was detected on July 1, 2025, by the NASA-funded ATLAS (Asteroid Terrestrial-impact Last Alert System) telescope in Rio Hurtado, Chile. This comet marks only the third known interstellar visitor to our cosmic neighbourhood, following ‘Oumuamua in 2017 and Comet 2I/Borisov in 2019.
The comet, initially dubbed A11pl3Z, is speeding toward the sun at an astonishing 68 kilometres per second, arriving from the direction of the constellation Sagittarius. Currently located about 670 million kilometres from Earth, 3I/ATLAS is on a hyperbolic trajectory, meaning the sun’s gravity does not bind it and will exit the solar system after its visit.
NASA assures that the comet poses no threat to Earth, maintaining a safe distance of at least 240 million kilometres during its closest approach in December 2025.
Astronomers estimate 3I/ATLAS to be approximately 20 kilometres in diameter, making it significantly larger than its interstellar predecessors.
For comparison, ‘Oumuamua was estimated at 100-200 meters in length, and Comet 2I/Borisov’s core was about 800 meters across. This makes 3I/ATLAS roughly 100–200 times larger than ‘Oumuamua and 50–100 times larger than Borisov’s core.
However, its size is comparable to the meteorite that struck the Yucatán Peninsula 65 million years ago, which formed the Chicxulub crater and is widely linked to the extinction of the dinosaurs. That meteorite, estimated at 10-15 kilometres in diameter, had a devastating impact, releasing energy equivalent to billions of atomic bombs.
The scale of 3I/ATLAS is approximately 10 times the mass of the Yucatan Chicxulub impactor and is composed mainly of water ice and volatiles, making it less dense but still formidable. The speed of 3I/ATLAS is estimated to be three times faster than that of a typical meteor, underscoring the immense energy it would carry if it were to impact a planet, although no such risk exists for Earth.
The comet’s brightness, currently at magnitude 18.8, suggests it may become visible to amateur telescopes as it nears its closest approach to the sun on October 30, 2025, at 1.4 astronomical units.
Astronomers worldwide are now racing to study 3I/ATLAS using ground-based observatories like the Rubin Observatory in Chile and potentially the James Webb Space Telescope. These observations aim to refine estimates of its size, composition, and surface properties, which could reveal clues about its origin in another star system.
Harvard astronomer Avi Loeb noted that the comet’s brightness may stem from a reflective coma of gas and dust, complicating size estimates, but its potential mass is “surprising” as high-mass objects are expected to be rarer.
Unlike the Chicxulub impactor, which caused catastrophic climate changes leading to a mass extinction, 3I/ATLAS is regarded as a harmless visitor in our solar system.
Sources: The Debrief, NASA, UIS Journal
