The mass of the sun changes due to the constant fusion of hydrogen atoms in its core, which transforms into helium and releases energy. This process is known as nuclear fusion and it is responsible for the sun's energy output and gradual decrease in mass.
The sun's mass is estimated to decrease by about 4 million tons per second due to fusion reactions. This may seem like a significant amount, but in comparison to the sun's overall mass of approximately 2 nonillion tons, it is a very small change.
While the sun's mass is primarily decreasing due to nuclear fusion, it is possible for it to experience an increase in mass. This can occur when the sun absorbs matter from other celestial bodies, such as when it captures comets or absorbs material from a nearby star.
The sun's mass is directly related to its energy output and therefore, its lifespan. As the sun's mass decreases, its core becomes denser and hotter, causing it to expand and become a red giant. This expansion will eventually lead to the end of the sun's life as it runs out of fuel for fusion.
While the sun's changing mass does not have a direct impact on Earth, it does affect the amount of energy and radiation that reaches our planet. A decrease in the sun's mass could result in a decrease in solar energy, potentially leading to a cooler climate. However, the effects of the sun's mass changes on Earth's climate are very complex and still being studied by scientists.