The apparent size of the Sun (with a physical diameter of about 865,000 miles [1.4 million kilometers]) varies with its distance from the observer. On Earth, where we average a distance of 93 million miles (150 million km) from our star, the angular diameter of the Sun is about half a degree (0.5°).
Mercury orbits the Sun at an average distance of about 36 million miles (58 million km). As a result, the angular diameter of the Sun from Mercury is much larger: about 1.4°. Venus’ average distance from the Sun is about 67 million miles (108 million km), and the Sun’s angular diameter from this planet is about 0.7°.
It is worth noting that the planets’ orbits are not quite circular. Between perihelion and aphelion, the angular diameter of the Sun as seen from Earth changes by about 3 percent. On Mercury, that change is nearly 53 percent, while on Venus, it’s a little over 1 percent.
Alison Klesman
Associate Editor
