An interstellar visitor is causing a stir, and its behaviour is becoming more baffling by the day. First spotted in July 2025, comet 3I/ATLAS is only the third object from beyond our solar system ever detected, and it is not acting like a typical comet.
As it whips past our Sun, new observations reveal a series of bizarre anomalies, forcing scientists to question our understanding of these celestial travellers.
Why Is Interstellar Visitor 3I/ATLAS Glowing Green?
3I/ATLAS was caught on camera glowing brightly as it shot across the sky, once again without a visible tail.
— Space and Technology (@spaceandtech_) November 10, 2025
(captured by: Chuck’s Astrophotography)pic.twitter.com/iPSg7u8tcc
Recent images from the Lowell Observatory in Arizona have captured the attention of astronomers worldwide. The pictures, taken by researcher Qicheng Zhang on 5 November 2025, show comet 3I/ATLAS glowing with an emerald hue.
This green colour, Zhang explains, is caused by hydrocarbon molecules breaking apart under the Sun's intense ultraviolet light.
This process creates pairs of carbon atoms, known as diatomic carbon (C2), which emit a green light when struck by sunlight. Zhang compares the reaction to human skin getting sunburnt, as UV rays break down molecules on the comet's surface.
The same images also appeared to show the comet without its signature tail. However, scientists at the Lowell Observatory assure that the tail is merely hidden, positioned directly behind the comet from our vantage point on Earth.
A faint glow to the left of the comet's coma, its thin atmosphere, hints at the dust tail we cannot see head-on.
What Unexplained Anomalies Surround Comet 3I/ATLAS?
While the green glow and 'hidden' tail have logical explanations, other characteristics of 3I/ATLAS are proving more difficult to decipher. Astrophysicists note that the comet brightened fivefold after its closest approach to the Sun, a phenomenon that is not fully understood.
It has also exhibited a strange 'anti-tail' pointing towards the Sun, rather than away from it.
Most puzzling is a discovery by NASA's Jet Propulsion Laboratory of a 'non-gravitational acceleration'. 3I/ATLAS is moving faster than the Sun's gravity alone can explain. While comets can get a propulsive kick from ice turning to gas and ejecting from the surface, this process should create a massive, visible tail.
Harvard astrophysicist Avi Loeb calculates that to achieve its current speed, the comet would need to have shed at least 13 per cent of its total mass.
Yet, images from Spain's R. Naves Observatory show no visible tail, challenging conventional comet models. Loeb stated that if 3I/ATLAS continues to show no tail, 'it is likely not a naturally-occurring comet'.
What Is the Origin and Significance of 3I/ATLAS?
Discovered on 1 July 2025 by an ATLAS telescope in Chile, 3I/ATLAS was quickly identified as an interstellar visitor due to its hyperbolic trajectory.
It follows in the footsteps of 'Oumuamua (2017) and Borisov (2019) as the third known object to enter our solar system from deep space.
Scientists believe the comet could be around 3 billion years older than our own solar system, offering a unique chance to study primordial material. Research suggests it may be covered by a radiation-hardened crust, formed over aeons of travelling through the cosmos.
NASA has confirmed the object poses no threat to Earth and will continue its journey out of our solar system at over 210,000 kilometres per hour. All eyes are now on NASA's Mars Orbiter, which has captured the highest-resolution images of the comet to date, though their release is delayed.
How Can You Observe Comet 3I/ATLAS?
As the comet moves higher above the horizon, it becomes accessible to more observers. For those hoping to catch a glimpse of this mysterious object, astronomers recommend using a 6-inch (15 cm) telescope.
Throughout November and December 2025, 3I/ATLAS will be visible just before sunrise, low in the eastern sky.
