The Sun

The sun is the real star of the show—literally! The closest star to Earth, it’s the source of all the heat and light that makes flowers bloom, songbirds croon, and sunbathers swoon. Life wouldn’t exist without it. It's also the center of our solar system and by far its largest object. More than a million Earths would fit inside the sun! Our star’s enormous gravity grips the planets, dwarf planets, asteroids, comets, keeping them from spinning into deep space. Put simply, we wouldn’t have a solar system without the sun.

Despite its importance in the grand scheme of things, the sun isn’t unique or particularly complex. It's average in size and middle-aged compared to the billions of other stars in our galaxy. And although the sun accounts for 99.8 percent of the total mass of the solar system, it's really just a big ball of gas. A process called nuclear fusion converts hydrogen to helium deep in the sun’s core, where temperatures hit a balmy 18 million degrees Fahrenheit (15.7 million degrees Celsius). Fusion creates energy that travels to the sun’s surface in a journey that lasts a million years. The core will run out of hydrogen gas eventually, which will put an end to our fun in the sun. But fear not: That day won’t come for at least another five billion years.

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