How Big Is The Sun?
QUICK ANSWER
The Sun has a diameter of about 865,000 miles (1.4 million km), roughly 109 times wider than Earth. About 1.3 million Earths could fit inside the Sun by volume. The Sun contains 99.8 percent of all the mass in our solar system, vastly more than every planet, moon, and asteroid combined.
The Sun is enormous. It's about 109 times wider than Earth, contains over a million Earths by volume, and accounts for 99.8 percent of all the matter in our solar system. Compared to other stars, though, the Sun is fairly average. Many stars are vastly larger.
How big is the Sun compared to Earth?
Huge. According to NASA, the Sun has a diameter of about 865,000 miles (1.4 million km), compared to Earth's 7,918 miles. That makes the Sun about 109 times wider than Earth. By volume, about 1.3 million Earths could fit inside the Sun. The mass ratio is even more extreme: the Sun is about 333,000 times more massive than Earth. If Earth were the size of a marble, the Sun would be a beach ball about 8 feet across.
How does the Sun compare to other planets?
It dwarfs everything. The Sun is about 10 times wider than Jupiter, the biggest planet in our solar system. Mercury, the smallest planet, would be barely visible against the Sun's disk. The Sun contains 99.8 percent of all the mass in our solar system. All the planets, moons, asteroids, and comets combined make up the remaining 0.2 percent. Jupiter alone is about 70 percent of that non-Sun mass, with Saturn another 20 percent. The inner rocky planets are essentially rounding errors in the solar system's mass distribution.
How does the Sun compare to other stars?
Average to small. The Sun is classified as a yellow dwarf, which sounds modest but is technically misleading. The Sun is bigger than about 80 percent of stars in our galaxy, since most stars are smaller red dwarfs. But there are stars vastly larger than the Sun. Betelgeuse, a red supergiant in the constellation Orion, is about 700 times wider than the Sun. UY Scuti, one of the largest known stars, is about 1,700 times wider. The Sun is large for an everyday star but small compared to the giants.
Is the Sun changing size?
Slowly, yes. The Sun has been gradually growing larger over its 4.5-billion-year lifetime as it converts hydrogen into helium in its core. The growth is too slow to notice on human timescales but adds up over billions of years. In about 5 billion years, the Sun will expand dramatically into a red giant, growing large enough to engulf the inner planets. After the red giant phase, the Sun will shed its outer layers and shrink down to a white dwarf about the size of Earth.
The Sun is about 109 times wider than Earth and contains 99.8 percent of the mass in our solar system. Compared to the planets it dwarfs them all; compared to other stars it's about average. The Sun has been slowly growing throughout its lifetime and will eventually expand into a red giant before shrinking to a small white dwarf at the end of its life.
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