Astronomers have officially identified a new interstellar object, designated 3I/ATLAS, that is currently traversing the outer solar system. Previously referred to as A11pl3Z, this object has now received an esteemed classification, with the “I” denoting its interstellar origins.
Located between the asteroid belt and Jupiter, 3I/ATLAS is approximately 416 million miles from the Sun, which is four and a half times the distance between Earth and our star, according to NASA. Its trajectory indicates it is rapidly nearing the inner solar system, speeding along at about 130,000 miles per hour — an astonishing velocity that Harvard’s Avi Loeb humorously compared to driving a thousand times over the highway speed limit.
Paul Chodas, director at NASA’s Jet Propulsion Laboratory’s Center for Near Earth Object Studies, remarked, “If you trace its orbit backward, it seems to be coming from the center of the galaxy, more or less. It definitely came from another solar system. We don’t know which one.”
3I/ATLAS marks the third confirmed interstellar visitor to enter our solar system. The first, ‘Oumuamua, was spotted in 2017 and gained notoriety for its elongated shape. The second, a comet named Borisov, was notable for disintegrating during its approach.
Early observations suggest that 3I/ATLAS is another comet, potentially making it the second known rogue comet. Its discovery involved an international collaborative effort; it was flagged as an asteroid by a Chilean telescope linked to the Asteroid Terrestrial-impact Last Alert System (ATLAS) on Tuesday. The International Astronomical Union’s Minor Planet Center swiftly added it to the list of confirmed near-Earth objects, a move endorsed by NASA.
Following this, over 100 observations were collected from telescopes worldwide, including reports of potential cometary activity, leading to its designation as 3I/ATLAS. Chodas confirmed to the New York Times, “There’s no uncertainty” regarding its interstellar roots, as its velocity indicates it cannot originate from our solar system.
Astronomers theorize that 3I/ATLAS likely formed as a comet around a distant star before being ejected from its original system, possibly due to gravitational interactions.
Determining the size of 3I/ATLAS remains a challenge. If it were a rocky asteroid, estimates suggest it would need to be around 12 miles wide to reflect current brightness levels. However, as a comet, measuring size is complicated due to its surrounding coma – a halo of gas and dust that amplifies its brightness as sunlight heats the object. For instance, Borisov’s coma was estimated to extend nearly 100,000 miles, about 14 times Earth’s size.
Chodas noted, “You can’t infer the size of the solid object from the brightness of the coma. So it’s too early to say how big this object is.”
Fortunately for astronomers, 3I/ATLAS will remain observable for a considerable period, unlike previous interstellar visitors such as ‘Oumuamua, which disappeared within weeks. Chodas stated, “It’ll be easily observable for astronomers around the world. It should be visible well into next year to large telescopes.”
The object is predicted to reach its closest approach to the Sun around October 30, coming within approximately 130 million miles, placing it inside Mars’ orbit.
