What force causes the ion (gas) tail of a comet to always point directly away from the Sun, regardless of the comet's direction of motion?

Answer and explanation

Correct answer: B. Solar wind and solar radiation pressure

  1. Step 1: As a comet nears the Sun, solar heating vaporizes volatile ices, forming a glowing envelope (coma) and releasing gas and dust.
  2. Step 2: The high-velocity solar wind (a stream of charged ions) and solar radiation pressure exert outward electromagnetic force on ionized gas molecules, pushing the ion tail directly away from the Sun.
Answer
Solar wind and solar radiation pressure
Why not the others: 'Gravitational repulsion from the Sun' Gravity is strictly an attractive force and pulls the comet toward the Sun; 'Centrifugal force from the comet's orbit' Centrifugal force acts outward from the orbital curvature center, not radially outward from the Sun; 'Friction with interplanetary dust' Friction with dust would trail behind the comet along its orbital velocity vector, not point radially outward from the Sun.

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