What surrounds the Sun, extending beyond the orbit of Pluto?

The correct answer is the Heliosphere. This is a vast bubble of solar wind and magnetic fields created by the Sun, which extends far beyond the orbit of Pluto. It acts as the Sun's protective shield, defining the boundary of the solar system and separating solar particles from the cosmic rays present in interstellar space.

The Heliosphere is significant because it helps protect planets, including Earth, from harmful cosmic radiation. Its outer boundary is known as the heliopause, where the solar wind slows down and merges with the interstellar medium. This structure directly correlates to the influence of solar activity on the surrounding space environment and is crucial for understanding space weather and its effects on satellites and other technologies.

The other options refer to different parts of the Sun or phenomena within our solar system but do not encompass the vast region that surrounds the Sun itself. For instance, the Photosphere is the visible surface of the Sun; the Atmosphere typically refers to the gases surrounding a planet like Earth; and the term Metrosphere is not a recognized term in this context.