A mysterious visitor from beyond the solar system
Astronomers around the world are closely tracking 3I/Atlas, an interstellar comet that has baffled scientists with its unusual trajectory, brightness, and behaviour. Some researchers have even speculated whether it might be an alien probe, sparking viral theories and public fascination.
First detected on July 1, 2025, by the ATLAS Survey Telescope in Chile, the comet has since been observed by the James Webb Space Telescope, Hubble, and the Very Large Telescope.
How do we know 3I/Atlas is from interstellar space?
Unlike comets that originate in the solar system, 3I/Atlas is traveling on a hyperbolic trajectory, indicating it came from outside our solar system. Its unusual speed and path set it apart from ordinary comets.
How fast is 3I/Atlas moving?
The comet is racing through space at nearly 221,000 km per hour (60,000 km/second), far faster than most solar system objects.
How old is 3I/Atlas?
According to a July 2025 study led by Matthew Hopkins, 3I/Atlas is estimated to be between 7.6 and 14 billion years old. This makes it older than the solar system itself, which formed about 4.6 billion years ago.
How big is 3I/Atlas?
Its exact size remains debated:
- Hubble observations: Nucleus likely between 0.32 and 5.6 km in diameter.
- Harvard’s Avi Loeb: Claims the nucleus could be as large as 46 km.
- Recent studies: Suggest its solid nucleus must be larger than 5 km, with a mass exceeding 33 billion tons.
When was 3I/Atlas first seen?
Though officially spotted on July 1, 2025, archival data shows NASA’s TESS telescope captured it as early as May 2025, when its brightness unexpectedly increased fivefold in less than a month, far more than the predicted 1.5 times.
What anomalies has it shown?
Scientists are puzzled by several features:
- Unusually high mass for a comet.
- Lack of a cometary tail for a long period.
- Extremely high velocity.
- Brightness anomalies, with Loeb even suggesting it may be emitting its own light.
- A trajectory that crosses paths with several planets in the solar system.
Is 3I/Atlas a threat to Earth?
No. NASA confirms the comet will not collide with Earth. Its closest approach will be in December 2025, at a safe distance of 1.8 AU (273 million km).
Where is 3I/Atlas now?
Currently, 3I/Atlas is about 523 million km (3.5 AU) away, moving inside Jupiter’s orbit. It is expected to reach perihelion (closest point to the Sun) on October 30, 2025.
Conclusion
Whether it is an ancient cosmic wanderer or something more mysterious, 3I/Atlas is giving astronomers a rare chance to study a true interstellar visitor. While alien theories grab attention, scientists stress that the object poses no danger to Earth.