Britannica Sources used in this answer

How does the solar wind create comet tails that point away from the Sun?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Space weather Earth's full North Polar auroral oval, in an image taken in ultraviolet light by the U.S. Polar spacecraft over northern Canada, April 6, 1996. In the colour-coded image, which simultaneously shows dayside and nightside auroral activity, the most intense levels of activity are red, and the lowest levels are blue. Polar, launched in February 1996, was designed to further scientists' understanding of how plasma energy contained in the solar wind interacts with Earth's magnetosphere.

The solar wind—a stream of protons and electrons flowing outward from the Sun—is the primary force responsible for creating the ion tails of comets that point directly away from the Sun.12

As a comet approaches the Sun, gas and dust are released from its nucleus to form a coma. Molecules within this coma are ionized through charge exchange with the solar wind. Once these particles become ionized, they are captured by the Sun’s magnetic field and accelerated away from the Sun at high velocities, typically around 400 km per second. Because this solar wind velocity is significantly higher than the comet's orbital speed, the resulting plasma tail is pushed into a straight, narrow configuration that extends directly away from the Sun.1

In contrast, the comet's dust tail is shaped by radiation pressure, which pushes tiny dust grains into a broader, curved path that also generally points away from the Sun but follows the comet's orbit.1