The sun lies at the heart of the solar system, where it is by far the largest object. (1)It holds 99.8 percent of the solar system's mass and is (2)roughly 109 times the diameter of the Earth — about one million Earths could fit inside the sun.

The sun was born roughly 4.6 billion years ago. Many scientists think the sun and the rest of the solar system formed from a giant, rotating cloud of gas and dust known as the solar nebula. As the nebula collapsed because of its gravity, it spun faster and flattened into a disk. Most of the material was pulled toward the center to form the sun.

(3)The visible part of the sun is roughly 10,000 degrees F (5,500 degrees C), while temperatures in the core reach more than 27 million degrees F (15 million degrees C), driven by nuclear reactions. One would need to explode 100 billion tons of dynamite every second to match the energy.

(4)The sun has enough nuclear fuel to stay much as it is now for another 5 billion years. After that, it will swell to become a red giant. Eventually, it will shed its outer layers, and the remaining core will collapse to become a white dwarf. Slowly, this will fade, to enter its final phase as a dim, cool object sometimes known as a black dwarf.

The sun and its atmosphere are divided into several zones and layers. The solar interior, from the inside out, is made up of the core, radiative zone and the convective zone. (5)The solar atmosphere above the zones consists of the photosphere, chromosphere, a transition region and the corona. Beyond that is the solar wind, an outflow of gas from the corona.

The core extends from the sun's center to about a quarter of the way to its surface. Although it only makes up roughly 2 percent of the sun's volume, it is almost 15 times the density of lead and holds nearly half of the sun's mass. Next is (6)the radiative zone, which extends from the core to 70 percent of the way to the sun's surface, making up 32 percent of the sun's volume and 48 percent of its mass.

Light from the core gets scattered in this zone, so that a single photon often may take a million years to pass through. (7)The convection zone reaches up to the sun's surface, and makes up 66 percent of the sun's volume but only a little more than 2 percent of its mass. Roiling "convection cells" of gas dominate this zone. Two main kinds of solar convection cells exist — granulation cells about 600 miles (1,000 kilometers) wide and supergranulation cells about 20,000 miles (30,000 kilometers) in diameter.

(8)The photosphere is the lowest layer of the sun's atmosphere, and emits the light we see. It is about 300 miles (500 kilometers) thick, although most of the light comes from its lowest third. Temperatures there range from 11,000 degrees F (6,125 degrees C) at bottom to 7,460 degrees F (4,125 degrees C) at top.

Next up is the chromosphere, which is hotter at up to 35,500 degrees F (19,725 degrees C) and is apparently made up entirely of spiky structures known as spicules typically some 600 miles (1,000 kilometers) across and up to 6,000 miles (10,000 kilometers) high. After that is the transition region a few hundred to a few thousand miles or kilometers thick, which is heated by the corona above it and sheds most of its light as ultraviolet rays.

At the top is the super-hot corona, which is made of structures such as loops and streams of ionized gas. (9)The corona generally ranges from 900,000 degrees F (500,000 degrees C) to 10.8 million degrees F (6 million degrees C) and can even reach tens of millions of degrees when a solar flare occurs. Matter from the corona is blown off as the solar wind.

(10)The strength of the sun's magnetic field is typically only about twice as strong as Earth's field. However, it becomes highly concentrated in small areas, reaching up to 3,000 times stronger than usual. These kinks and twists in the magnetic field develop because the sun spins more rapidly at the equator than at the higher latitudes and because the inner parts of the sun rotate more quickly than the surface. These distortions create features ranging from sunspots to spectacular eruptions known as flares and coronal mass ejections. Flares are the most violent eruptions in the solar system, while coronal mass ejections are less violent but involve extraordinary amounts of matter — a single ejection can spout roughly 20 billion tons (18 billion metric tons) of matter into space.

Energy from the Sun is very important to the Earth. The Sun warms our planet, heating the surface, the oceans and the atmosphere. This energy to the atmosphere is one of the primary drivers our weather. Our climate is also strongly affected by the amount of solar radiation received at Earth. That amount changes based on the Earth’s albedo, that is how much radiation is reflected back from the Earth’s surface and clouds.