Comet tail

They become visible through different phenomena: the dust reflects sunlight directly, and the gases glow from ionization.

In the outer Solar System, comets remain frozen and are extremely difficult or impossible to detect from Earth due to their small size.

The streams of dust and gas thus released form a huge, extremely tenuous atmosphere around the comet called the coma, and the force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous tail to form, which points away from the Sun.

[5] While the solid nucleus of comets is generally less than 30 km across, the coma may be larger than the Sun, and ion tails have been observed to extend 3.8 astronomical units (570 Gm; 350×10^6 mi).

The comet and its induced magnetic field form an obstacle to outward flowing solar wind particles.

[13] Venus possesses a similar tail due to the induced magnetosphere formed by interaction of the solar wind with the venusian atmosphere.