The Sun: Our Nearest Star and the Heart of Your Sign

What is the Sun?

The Sun is a star: a ball of hot gas, mostly hydrogen and helium, that makes its energy by fusing hydrogen into helium in its core. It is about 1.39 million km across, 109 times Earth’s width, and holds more than 99.8% of all the mass in the solar system. Earth orbits it at an average of 149.6 million km, a distance astronomers call one astronomical unit (au), so its light reaches us about 8 minutes and 20 seconds after it leaves the surface. The Sun is about 4.6 billion years old.

Where the Sun is in the sky

The ecliptic is the path the Sun appears to follow across our sky over a year, the plane of Earth’s orbit seen from Earth. Positions along it are measured in degrees, from 0° at the March equinox to 360°. The zodiac divides it into twelve equal 30° parts named after signs: Aries covers 0° to 30°, Taurus 30° to 60°, and so on. The signs are counted from the equinox, not from the star patterns they were named after; those constellations now sit about 24° further along, because Earth’s axis slowly wobbles (precession).

The Sun defines the ecliptic, so it is always on it (0° latitude). As Earth moves around its orbit, the Sun seems to move about 1° a day against the background stars and spends about 30 days in each sign, going all the way around in one year. It always moves forward: it never goes retrograde. Its entry into Aries, Cancer, Libra and Capricorn marks the March equinox, the June solstice, the September equinox and the December solstice.

The Sun in astrology

In astrology the Sun stands for your core self: identity, vitality, will and the way you shine. Your Sun sign, the sign the Sun was in when you were born, is the sign you read for in a daily horoscope. The Sun rules Leo. As it moves through the signs, it lights up a different area of life for each sign each month, shown below.