What inconsistency exists regarding 'Oumuamua's trajectory?

• A. It shows acceleration consistent with solar radiation pressure.
• B. It is inconsistent with hydrogen gas release from water ice.
• C. It supports hydrogen gas release as the cause.
• D. It indicates gravitational interactions with planets.

Answer: (A)

The key idea is that the path of this object cannot be explained by gravity alone. The data show a small, persistent acceleration as it moved away from the Sun, in a direction consistent with sunlight pushing on it. That kind of push fits solar radiation pressure, which would occur if the object has an unusually high surface-area-to-mass ratio—think a very thin, sail-like shape. If hydrogen gas release from water ice were driving the motion, we’d expect a visible coma or tail and spectral signs of gas, which weren’t observed, so that explanation doesn’t fit the trajectory. Gravitational interactions with planets would produce different, more noticeable deflections than what the data show.