Sometimes, space has a way of surprising even the people who spend their lives studying it. Astronomers believed they had been tracking a near-Earth asteroid called 1998 SH2 for nearly three decades. But when NASA pointed its radar toward the object in 2025, it simply wasn’t where it was supposed to be. That unexpected disappearance led scientists down a very different path, eventually revealing that the object wasn’t an asteroid after all, it was a comet hiding in plain sight. Here’s everything you need to know about the discovery.
A Routine Observation Turned Into A Space Mystery
The surprising discovery has been detailed in a new study published in Nature Astronomy. Researchers had followed the object’s orbit since 1998 and expected it to behave like a typical asteroid. However, during an observation campaign in August 2025, NASA’s Deep Space Network failed to detect it at its predicted location. That immediately raised questions.
The study says that scientists realised that 1998 SH2 was drifting slightly away from its expected orbit because something other than gravity was affecting its motion.
“After we measured the nongravitational perturbations affecting the motion of 1998 SH2 and recognised they weren’t compatible with the object being an asteroid, we suspected the object could be an active comet,” said Davide Farnocchia, a navigation engineer at NASA‘s Jet Propulsion Laboratory and lead author of the study.
The team concluded that the object was likely releasing tiny amounts of gas into space. Although the force was extremely small, it was enough to gradually alter its orbit over time.
Powerful Telescopes Finally Revealed The Truth
To test their theory, researchers turned to several observatories, including the Canada-France-Hawaii Telescope and the European Southern Observatory’s Very Large Telescope in Chile. “The images we collected from these observatories showed a weak but clear tail, thus confirming that 1998 SH2 is, in fact, a comet,” said Olivier Hainaut, an astronomer at the European Southern Observatory and co-author of the study.
Following the discovery, the object received a new comet designation: P/1998 SH2. The finding may also help explain a mysterious group of celestial objects known as dark comets, which resemble asteroids but behave more like comets. Researchers believe some of these objects could simply have tails too faint to detect with conventional observations.
Farnocchia said the discovery highlights why continuous monitoring of near-Earth objects remains critical, not only for understanding how these bodies evolve but also for improving planetary defence efforts by identifying potential Earth-impact risks more accurately.