Astronomy Practice Exam 2026 – Complete Preparation Guide

The corona is correctly identified as the Sun's outer atmosphere, which consists of thin, hot gases. It is a region that extends millions of kilometers into space and is characterized by a relatively low density and high temperature, which can reach temperatures of about 1 to 3 million degrees Kelvin.

The unique properties of the corona make it an intriguing subject of study. Despite being farther from the core of the Sun, where nuclear fusion occurs, it exhibits such high temperatures that they are still not fully understood; one key aspect is the presence of the solar wind, a stream of charged particles released from the corona. The corona becomes visible during a solar eclipse when the brighter light from the Sun's surface is obscured, revealing its delicate structure and any solar activity occurring there.

Other choices describe different layers or components of the Sun or its phenomena rather than accurately depicting the corona. Thus, understanding the corona is vital to grasping solar dynamics and the behavior of the Sun as a whole.