Astronomers spotted the 31/ATLAS an interstellar comet currently traversing our Solar System. It is the third interstellar visitor after ‘Oumuamua (2017) and 2I/Borisov (2019) this object is generating buzz for its peculiar path, infrequent origin and newly developing cometary features the scientists are observing with interest.
Is 31/ATLAS Confirmed as an Interstellar Object?
The 31/ATLAS survey telescope at Rio Hurtado in Chile detected the object on 1 July 2025. Its hyperbolic orbit or not gravitationally bound to the Sun verifies that it originated from beyond our Solar System.
31/ATLAS: Distance, Brightness & Visibility
At discovery 3I/ATLAS was approximately 670 million kilometers from the Sun outside Jupiter’s orbit. It is now observable with ground-based telescopes and will continue to be so up to September 2025 and it is getting brighter as it nears perihelion.
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31/ATLAS: Size & Physical Properties
31/ATLAS Observations indicate its nucleus might range from 0.32 km to 5.6 km in diameter and this largely depends on how much light is from its coma (the gas and dust halo).
It is traveling at about 60 km/s relative to the Sun with a course that will carry it nearest the Sun on October 30, 2025, at a distance of approximately 1.4 astronomical units barely within the orbit of Mars. It is not a threat to Earth.
31/ATLAS: Coma & Tail Development
Although at first sight it seems to be faint, it has acquired a coma the bright envelope surrounding a comet and a brief tail as verified through observations with telescopes like Gemini South.
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Tail development is anticipated to persist with growing solar heating. Spectroscopy particularly with JWST finds 3I/ATLAS to be dominated by carbon dioxide in its coma together with water, carbon monoxide and other dust particles. The CO₂ and H₂O ratio appears unusually high relative to most Solar System comets.
31/ATLAS the observation window & visibility
Its discovery period up to late 2025 3I/ATLAS will remain in sight of ground‑based telescopes. It is visible from September until its nearness to the Sun makes it hard to observe. It comes back into view from behind the Sun in early December. The object will not come close to Earth threateningly its nearest Earth‑Sun distance remains well and large.
How Unusual is it Polarizations & Rare Features?
Polarimetric observations indicate 3I/ATLAS possesses an extremely deep negative polarization branch at low phase angles unusual in normal comets and asteroids. In late October the object will pass behind the Sun in our view, rendering observation less easy.
It will be seen again in early December still observable but far enough away from Earth to be safe. Scientists intend observing as much as possible both before and after perihelic transit.
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