A mysterious traveller from beyond our Solar System is paying Earth a rare visit. This interstellar comet 3I/ATLAS has captured the attention of astronomers and sky-watchers alike as it makes its closest approach to Earth on 29 October 2025. Racing through space at incredible speed, 3I/ATLAS is not just a spectacle of cosmic beauty but a scientific treasure, carrying ancient material formed around distant stars.
Unlike typical comets, this one originated far outside our Solar System, offering scientists an extraordinary glimpse into the building blocks of other worlds. While it poses no threat to Earth, its arrival presents a once-in-a-lifetime opportunity to study the mysteries of interstellar space and the origins of planetary systems.
How 3I/ATLAS was discovered: The third confirmed visitor from another star system
3I/ATLAS was first detected in July 2025 by astronomers using the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Hawaii. From its very first observations, the object stood out. Its speed was far greater than that of typical comets bound by the Sun’s gravity, and its orbit followed a hyperbolic trajectory, meaning it would pass through the Solar System just once before heading back into interstellar space.
Four major space observatories later confirmed its interstellar nature. Theoretical physicist Michio Kaku described it as a “mystery interstellar object” travelling through the Solar System on a hyperbolic path. Its composition and motion suggested it originated far beyond the outer edges of our planetary neighbourhood, possibly from another star system.
How close will 3I/ATLAS come to Earth
Despite the global buzz, 3I/ATLAS will not come anywhere near Earth in a threatening way. On 29 October 2025, it will reach its closest approach at about 1.8 astronomical units (167 million miles) from our planet. In cosmic terms, that’s a safe distance nearly twice the span between the Earth and the Sun.
This proximity still allows astronomers to observe it in great detail, using both ground-based telescopes and space observatories. The event marks an exciting period for researchers who will gather critical data about its composition, chemical structure, and activity near the Sun.
What makes 3I/ATLAS unique among comets
Unlike the countless comets that orbit the Sun in regular cycles, 3I/ATLAS is a one-time visitor. Its hyperbolic orbit means it was likely ejected from another star system, possibly after a gravitational interaction with a large planet. Once it passes near the Sun, it will continue its journey outward and never return.
The comet is already showing unusual activity. Astronomers have observed it ejecting massive jets of gas and dust toward the Sun, a striking feature that distinguishes it from typical Solar System comets. These jets are powered by the rapid sublimation of ice as the comet heats up, revealing complex chemistry that may differ from the compositions seen in comets native to our system.
Composition and structure of 3I/ATLAS
The nucleus of 3I/ATLAS is the solid core at its centre and is estimated to be less than one kilometre wide. Surrounding this small body is a vast cloud of gas and dust called the coma, which glows brightly as it interacts with sunlight.
Spectroscopic observations show that the comet contains carbon dioxide, hydrogen cyanide, and atomic nickel vapour, giving it a faint greenish-blue glow. These chemicals are typical in frozen objects that formed in extremely cold environments, suggesting 3I/ATLAS was born far from any star’s heat.
As it moves closer to the Sun, the rising temperature is causing its surface ices to vaporise, producing unique emissions that scientists are using to trace its molecular composition. These emissions could reveal ancient organic materials, perhaps even the same molecules that seeded the early Earth with the building blocks of life.
Scientists race to decode 3I/ATLAS’s mysterious tail and orbit
Astronomers worldwide are racing to study the comet as it approaches the point where it comes closest to the Sun. Harvard astrophysicist Avi Loeb, known for his controversial ideas about ʻOumuamua, has suggested that 3I/ATLAS’s unusual movement could hint at non-natural origins, though this is still speculative. Most experts, however, agree that the comet is a natural relic of planetary formation in another star system which is considered as a time capsule of materials from the galaxy’s distant past.
Can 3I/ATLAS be seen without a telescope
Unfortunately, 3I/ATLAS is not visible to the naked eye. Its current brightness level ranges from magnitude 12 to 14, which requires a large telescope of at least 8 inches (200mm) in aperture to observe clearly.
For now, the comet is temporarily hidden due to its proximity to the Sun, a period astronomers call solar conjunction. It is expected to reappear around December 2025, when it becomes visible again from the Northern Hemisphere under dark, clear skies.
Those equipped with suitable telescopes will be able to witness its elongated tail and glowing coma, especially as it brightens while leaving the Sun’s vicinity.
Safety and prevention tips for sky-watchers
3I/ATLAS on 29 October: Related FAQs
What does the name 3I/ATLAS mean?
“3I” stands for the third interstellar object ever detected, while “ATLAS” refers to the Hawaiian observatory system that discovered it.
How long will 3I/ATLAS stay in our Solar System?
It will remain visible for several months as it passes through the inner Solar System but will eventually leave permanently, never to return.
Can 3I/ATLAS impact Earth or other planets?
No, its orbit keeps it far from any planets, including Earth. It poses absolutely no collision threat.
Why are scientists so interested in interstellar comets?
They contain material from other star systems, offering clues about how planets and comets form elsewhere in the galaxy.
How is 3I/ATLAS different from ʻOumuamua and 2I/Borisov?
ʻOumuamua appeared asteroid-like and lacked a tail, while 2I/Borisov resembled a typical comet. 3I/ATLAS displays both cometary features and unique gas emissions, providing a new perspective on interstellar matter.
Also Read | CAUTION! Southern ocean is building a hidden ‘burp’ of heat that could warm the planet all over again
Unlike typical comets, this one originated far outside our Solar System, offering scientists an extraordinary glimpse into the building blocks of other worlds. While it poses no threat to Earth, its arrival presents a once-in-a-lifetime opportunity to study the mysteries of interstellar space and the origins of planetary systems.
How 3I/ATLAS was discovered: The third confirmed visitor from another star system
3I/ATLAS was first detected in July 2025 by astronomers using the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Hawaii. From its very first observations, the object stood out. Its speed was far greater than that of typical comets bound by the Sun’s gravity, and its orbit followed a hyperbolic trajectory, meaning it would pass through the Solar System just once before heading back into interstellar space.
Four major space observatories later confirmed its interstellar nature. Theoretical physicist Michio Kaku described it as a “mystery interstellar object” travelling through the Solar System on a hyperbolic path. Its composition and motion suggested it originated far beyond the outer edges of our planetary neighbourhood, possibly from another star system.
How close will 3I/ATLAS come to Earth
Despite the global buzz, 3I/ATLAS will not come anywhere near Earth in a threatening way. On 29 October 2025, it will reach its closest approach at about 1.8 astronomical units (167 million miles) from our planet. In cosmic terms, that’s a safe distance nearly twice the span between the Earth and the Sun.
This proximity still allows astronomers to observe it in great detail, using both ground-based telescopes and space observatories. The event marks an exciting period for researchers who will gather critical data about its composition, chemical structure, and activity near the Sun.
What makes 3I/ATLAS unique among comets
Unlike the countless comets that orbit the Sun in regular cycles, 3I/ATLAS is a one-time visitor. Its hyperbolic orbit means it was likely ejected from another star system, possibly after a gravitational interaction with a large planet. Once it passes near the Sun, it will continue its journey outward and never return.
The comet is already showing unusual activity. Astronomers have observed it ejecting massive jets of gas and dust toward the Sun, a striking feature that distinguishes it from typical Solar System comets. These jets are powered by the rapid sublimation of ice as the comet heats up, revealing complex chemistry that may differ from the compositions seen in comets native to our system.
Composition and structure of 3I/ATLAS
The nucleus of 3I/ATLAS is the solid core at its centre and is estimated to be less than one kilometre wide. Surrounding this small body is a vast cloud of gas and dust called the coma, which glows brightly as it interacts with sunlight.
Spectroscopic observations show that the comet contains carbon dioxide, hydrogen cyanide, and atomic nickel vapour, giving it a faint greenish-blue glow. These chemicals are typical in frozen objects that formed in extremely cold environments, suggesting 3I/ATLAS was born far from any star’s heat.
As it moves closer to the Sun, the rising temperature is causing its surface ices to vaporise, producing unique emissions that scientists are using to trace its molecular composition. These emissions could reveal ancient organic materials, perhaps even the same molecules that seeded the early Earth with the building blocks of life.
Scientists race to decode 3I/ATLAS’s mysterious tail and orbit
Astronomers worldwide are racing to study the comet as it approaches the point where it comes closest to the Sun. Harvard astrophysicist Avi Loeb, known for his controversial ideas about ʻOumuamua, has suggested that 3I/ATLAS’s unusual movement could hint at non-natural origins, though this is still speculative. Most experts, however, agree that the comet is a natural relic of planetary formation in another star system which is considered as a time capsule of materials from the galaxy’s distant past.
Can 3I/ATLAS be seen without a telescope
Unfortunately, 3I/ATLAS is not visible to the naked eye. Its current brightness level ranges from magnitude 12 to 14, which requires a large telescope of at least 8 inches (200mm) in aperture to observe clearly.
For now, the comet is temporarily hidden due to its proximity to the Sun, a period astronomers call solar conjunction. It is expected to reappear around December 2025, when it becomes visible again from the Northern Hemisphere under dark, clear skies.
Those equipped with suitable telescopes will be able to witness its elongated tail and glowing coma, especially as it brightens while leaving the Sun’s vicinity.
Safety and prevention tips for sky-watchers
- Avoid direct sunlight observation – Never point telescopes or binoculars toward the Sun while searching for the comet, as this can cause permanent eye damage.
- Use proper filters – Employ solar filters when observing near sunrise or sunset to protect your eyes and equipment.
- Plan viewing during dark hours – Choose nights with minimal moonlight and low light pollution for the best visibility.
- Follow official updates – Stay informed through NASA, ESA, or observatory announcements for accurate viewing times and locations.
- Keep equipment stable – Use a tripod or tracking mount to avoid blurring caused by Earth’s rotation.
3I/ATLAS on 29 October: Related FAQs
What does the name 3I/ATLAS mean?
“3I” stands for the third interstellar object ever detected, while “ATLAS” refers to the Hawaiian observatory system that discovered it.
How long will 3I/ATLAS stay in our Solar System?
It will remain visible for several months as it passes through the inner Solar System but will eventually leave permanently, never to return.
Can 3I/ATLAS impact Earth or other planets?
No, its orbit keeps it far from any planets, including Earth. It poses absolutely no collision threat.
Why are scientists so interested in interstellar comets?
They contain material from other star systems, offering clues about how planets and comets form elsewhere in the galaxy.
How is 3I/ATLAS different from ʻOumuamua and 2I/Borisov?
ʻOumuamua appeared asteroid-like and lacked a tail, while 2I/Borisov resembled a typical comet. 3I/ATLAS displays both cometary features and unique gas emissions, providing a new perspective on interstellar matter.
Also Read | CAUTION! Southern ocean is building a hidden ‘burp’ of heat that could warm the planet all over again
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