NASA Study Finds Near-Earth Asteroid 1998 SH2 Is Actually an Active Comet

What was once thought to be a plain asteroid has turned out to be something far more dynamic. NASA scientists have confirmed that near-Earth object 1998 SH2, long catalogued as an asteroid, is in fact an active comet. The revelation came after the object exhibited non-gravitational acceleration — a sudden change in its trajectory that could not be explained by gravity alone.

This shift in course, detected by telescopes and orbital tracking systems, is a classic signature of cometary activity. When a comet approaches the Sun, its icy nucleus heats up, releasing gas and dust. That outgassing acts like a small thruster, altering the object's path. 1998 SH2 had been quiet for decades, but new observations caught it in the act.

Asteroid or Comet? The Blurred Lines

The classification of objects in our solar system is not always straightforward. 1998 SH2 was originally labelled an asteroid because it lacked the bright coma and tail typical of comets. But recent data from NASA and the scientific journal Nature revealed that the object had been shedding material all along, just not enough to be easily noticed.

Researchers have termed objects like this 'dark comets' — asteroids that show cometary behaviour without the usual dramatic display. They are difficult to spot because their outgassing is faint, often only detectable by the subtle push it gives to their orbit.

What the Discovery Means

This finding is not just a curiosity. Active comets that were once considered asteroids can tell us about the early solar system. They carry pristine ice and organic material from billions of years ago. When one of these objects approaches Earth, it becomes a natural laboratory.

Non-gravitational acceleration is the key clue. For 1998 SH2, the measured change in speed was small but unmistakable. This data, published in Nature, matched computer models of comet outgassing. The object had a tail, but it was visible only in certain wavelengths of light, escaping routine surveys.

Solving Interstellar Mysteries

The study of 'dark comets' may also help explain where some interstellar objects come from. When comets from other star systems pass through our solar system, they often show irregular motion. If we understand how our own dark comets behave, we can better interpret the behaviour of visitors like 'Oumuamua.

Scientific American reported that these findings could "help solve interstellar mysteries." The logic is straightforward: if a dark comet from our own solar system can change course without a visible tail, the same could be true for objects from beyond. This makes tracking their origin far more complex.

For now, 1998 SH2 continues to orbit the Sun. It will remain classified as both an asteroid and a comet — a dual identity that scientists say is more common than previously thought.

What comes next is closer observation. NASA and other space agencies are expected to retrain telescopes on 1998 SH2 during its next close approach. The hope is to catch more of these dark comets before they slip by unnoticed.