The object, named 3I/Atlas, was first detected in July and is racing toward the Sun at nearly 61 kilometers per second (about 200,000 kilometers per hour). What makes it truly extraordinary is its origin—3I/Atlas is only the third known interstellar object ever observed, following the groundbreaking discoveries of ‘Oumuamua in 2017 and 2I/Borisov in 2019.
“This is a once-in-a-generation opportunity,” said Dr. Rebecca Allen, co-director of Swinburne’s Space Technology and Industry Institute. “We’ve never had an object like this to study before.”
The comet’s name reflects its background: the “3” signifies it is the third interstellar object discovered, the “I” stands for “interstellar,” and “Atlas” comes from the Asteroid Terrestrial-impact Last Alert System, the telescope network that first spotted it.
Though some space enthusiasts may be tempted to speculate about extraterrestrial technology—as they did with ‘Oumuamua—scientists are confident 3I/Atlas is a comet.
“There’s no evidence it’s anything other than a really fun space rock that came from outside the solar system,” said Dr. Laura Driessen, a radio astronomer at the University of Sydney. “Which, to be honest, is cool enough.”
Images from the Hubble Space Telescope show 3I/Atlas as a hazy “snowball,” surrounded by a coma of dust and gas formed as sunlight warms its surface. A faint comet tail has also been detected.
That dusty glow carries vital information. As the comet edges closer to the Sun, its gases will become more pronounced, giving scientists the chance to study its chemical signatures.
“Spectroscopy allows us to use light to decode exactly what this material is made of,” explained Allen. “It might reveal whether this comet formed in a solar system similar to ours—or in one that was completely different.”
Preliminary measurements suggest 3I/Atlas is relatively small, between 320 meters and 5.6 kilometers in diameter. Unlike familiar comets such as Halley’s, which loop around the Sun on predictable orbits, 3I/Atlas is on a hyperbolic path. Moving too fast to be captured by the Sun’s gravity, it will swing through the inner solar system—passing between Earth’s and Mars’ orbits—before vanishing back into interstellar space.
“This is a flyby,” Allen said. “It won’t be back. Once it exits, it’s gone forever.”
For backyard astronomers hoping for a dazzling show, expectations should be tempered. According to Con Stoitsis, comet and meteor director at the Astronomical Society of Victoria, 3I/Atlas will brighten as it approaches the Sun but will remain faint.
