What has puzzled researchers about 'Oumuamua's acceleration?

• A. It cannot be entirely explained by the gravitational pull of nearby bodies, indicating a nongravitational influence.
• B. It is fully explained by gravitational interactions.
• C. It accelerates due to dark matter.
• D. It slows down as expected from air resistance.

Answer: (B)

The key idea is whether gravity from the Sun and other bodies can fully explain an object's change in speed and direction. When researchers tracked 'Oumuamua, they found a small, persistent acceleration that did not fit the path expected from gravity alone. That extra push suggests a nongravitational influence was at work.

Two common ideas to explain such a push are outgassing, where ices vaporize and eject gas like a tiny rocket, and solar radiation pressure, where light from the Sun pushes on a very thin, reflective object. The puzzling part is that no visible coma or tail appeared to accompany the acceleration, which made it tricky to pin down the exact cause. Nevertheless, the measurements indicated that gravity alone couldn’t account for the observed trajectory, pointing researchers toward nongravitational forces as the explanation.