SUN'S SIZE

The Sun, as viewed from Earth, appears to have a diameter of about 1.39 million kilometers (864,340 miles). However, when we talk about how much of the Sun's surface we can see, it is important to note that we are limited by our perspective from Earth. Due to the Sun's immense distance from us, we can only observe its outermost layer, known as the photosphere.

The photosphere represents the visible surface of the Sun, and it extends about 500 kilometers (310 miles) below the Sun's visible edge. Therefore, the portion of the Sun's surface that we can see from Earth is a relatively thin layer, comprising only a small fraction of its total volume.

In terms of the Sun's size compared to other stars, it is considered an average-sized star. While the Sun may appear to be quite large to us, it is dwarfed by some of the largest stars known to exist. For instance, the star UY Scuti is estimated to be over 1,700 times larger in radius than the Sun, making it one of the largest known stars.

However, it is important to note that the Sun is still an incredibly significant and vital star for us. Its size and characteristics make it possible for life to exist on Earth, and its energy sustains us and the entire planetary system.