In an extraordinary and unprecedented finding, astronomers have identified a new interstellar object (ISO) traveling within our Solar System — the third one from outside confirmed to visit. Similar to ʻOumuamua in 2017, this visitor is on a fast-moving, hyperbolic path, indicating it is not gravitationally bound to the Sun and will pass once through, then leave into interstellar space.
Discovery and Designation
The object, officially designated 3I/ATLAS (also known as C/2025 N1), was first observed by the ATLAS (Asteroid Terrestrial-impact Last Alert System) survey telescope in Chile on 1 July 2025.
Soon after, follow-up observations and orbit calculations confirmed that its trajectory is hyperbolic — that is, its path is not a closed ellipse, and it is traveling fast enough to escape the Sun’s gravitational pull.
The "3I" prefix indicates that this is the third interstellar object known to pass through our Solar System, following 1I/ʻOumuamua (2017) and 2I/Borisov (2019).
Trajectory, Speed, and Path
Speed and Motion
3I/ATLAS is traveling very, very fast: when first spotted, its excess (unbound) speed with respect to the Sun was approximately 58 km/s (~ 130,000 mph or ~210,000 km/h).
As it gets closer to the Sun, gravitational acceleration will continue to boost its instantaneous velocity.
Orbital Path
It is highly hyperbolic in nature, which means the object is just passing by and will not be captured by solar gravity.
It seems to have originated from close to the direction of the constellation Sagittarius, heading toward the central part of our galaxy.
When at closest approach (perihelion), 3I/ATLAS will go within the Martian orbit, but still well away from Earth (~1.8 astronomical units from Earth at minimum) — collision risk zero.
Physical Characteristics and Activity
Observations are that 3I/ATLAS is comet-like in its appearance: it has a coma (a gas-and-dust envelope) and possibly a weak tail. This indicates it must have volatile ices that evaporate when heated by the Sun.
The diameter of its nucleus is difficult to quantify due to the bright coma blocking the center. The latest estimates put the diameter of the nucleus between 0.32 km to ~5.6 km.
The object's appearance is not like that of any other common asteroid; instead, it is more similar to known comets, with changing outgassing as it heads toward perihelion.
Significance: Why This Matters
Rare Visitors
Interstellar objects that travel through our Solar System are very uncommon. With ʻOumuamua and 2I/Borisov being the only other verified so far, every new ISO presents a rare opportunity to research material outside our stellar neighborhood.
Exploring Distant Origins
Since 3I/ATLAS has a extraheliodic origin, its composition and activity could still hold secrets about the context within its parent star system. From factors like the ices/dust/organics ratios, one could uncover how planetary systems elsewhere develop.
Testing Models & Theories
Its speed, path, and outgassing history are recorded, offering a test to models of the behavior of interstellar objects when they enter solar systems. The information improves our knowledge of how many similar objects there are that drift through the galaxy and how easily they can be detected.
In the future: Observation and Prospects
3I/ATLAS will come closest to the Sun on approximately 30 October 2025 at around 1.4 astronomical units (~210 million km) from the Sun.
Once past perihelion, the object will return into interstellar space — never to be seen again.
Along its journey, astronomers will use ground-based observatories, space telescopes, and potentially coordinated campaigns to measure brightness changes, spectral features, dust production, and so on.
Any atypical behavior — e.g., non-gravitational acceleration, fragmentation, or unexpected chemical signatures — would be particularly fascinating.
Echoes of ʻOumuamua and Borisov
Whereas ʻOumuamua brought global attention for its unusual shape and unexplained acceleration, and 2I/Borisov was a closer likeness to a normal comet, 3I/ATLAS provides a transition between unfamiliarity and familiarity. Its higher velocity and lightness could make it one of the most intensively examined interstellar visitors to date.
All of these travelers open our window into the
universe — reminding us that our Solar System is not alone, but is a part of an
active galaxy with objects moving in and out on astronomical timescales.
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