Kathrine Frich
For as long as humans have looked to the skies, space has stirred curiosity, fear and imagination.
The idea that life might exist beyond Earth remains one of science’s most enduring questions.
That fascination has been reignited by a fast-moving interstellar visitor whose behaviour is puzzling some researchers as it approaches the inner solar system.
The object, known as 3I/ATLAS, has been labelled by some commentators as a “potentially hostile alien threat”, a description that reflects speculation rather than any confirmed danger.
Watching the skies
Theoretical physicist Avi Loeb has been closely tracking 3I/ATLAS as it travels toward Earth.
According to NASA, the object is only the third known interstellar body discovered passing through the solar system.
Loeb has previously argued that some of its characteristics are unusual enough to raise questions about whether it is purely natural.
As the object draws nearer, fresh observations have added to that debate.
The comet is expected to make its closest approach to Earth on 19 December, prompting increased scrutiny from astronomers around the world.
A colour shift
Loeb recently highlighted what he described as a striking change in the object’s appearance after it passed perihelion, the point in its orbit closest to the Sun.
Writing on Medium, he said:
“The post-perihelion image combines exposures through four filters, blue, green, orange, and red, and its peak brightness is centered on the nucleus 3I/ATLAS.”
He added: “The color of the glowing halo appears green, possibly as a result of diatomic carbon (C2) molecules which emit green light.”
By contrast, earlier observations showed something different.
“A pre-perihelion image, posted on September 4, 2025, from the twin 8.1-meter telescope Gemini South in Chile, displayed a red colour of the glow around 3I/ATLAS,” Loeb wrote.
Possible explanations
Addressing the shift, Loeb suggested a change in the material released by the object as it neared the Sun.
“The change in colours from red to green means that the molecular composition of the plume of gas shed by 3I/ATLAS had changed near the Sun,” he said.
He also pointed to a glow surrounding the object that he had not previously observed, describing it as a “plume of gas” that he believes may be linked to gamma rays.
According to Loeb, the burst was first detected around the time 3I/ATLAS was discovered and was later followed by a supernova event.
He wrote: “A seven-hour gamma-ray burst should therefore coincide to within 17 degrees of the arrival direction of 3I/ATLAS once per 670 years.”
Scientists says that none of these observations confirm the presence of alien technology or life.
Most researchers maintain that natural explanations are far more likely.
Sources: NASA, Medium
