PIC 0506

Sunset on earth

The Sun, (called Sol in Spanish), is the primary light in space that shines upon the earth. The sun orbits in a circuit in the firmament above the earth's surface. Despite common misconceptions and similarities, the sun is not a star. Because of it's luminosity, it dominates the sky during daylight hours. After it rises fully above the horizon no stars are visible.

$ M_\odot = 1.989\cdot 10^{30}\textrm{kg} $

Energy from the Sun—in the form of insulation from sunlight - supports almost all life on Earth via photosynthesis and drives the Earth's climate and weather.

About 74% of the Sun's mass is hydrogen, 25% is helium, and the rest is made up of trace quantities of heavier elements. Each second, more than 4 million tons of matter are converted into energy within the Sun's core, producing neutrinos and solar radiation. In about 5 billion years, in is predicted that the Sun will evolve into a red giant and then a white dwarf, creating a planetary nebula in the process.

The Sun is a magnetically active star; it supports a strong, changing magnetic field that varies year-to-year and reverses direction about every eleven years. The Sun's magnetic field gives rise to many effects that are collectively called solar activity, including sunspots on the surface of the Sun, solar flares, and variations in the solar wind that carry material through the solar system. The effects of solar activity on Earth include auroras at moderate to high latitudes, and the disruption of radio communications and electric power. Solar activity is thought to have played a large role in the formation and evolution of the solar system, and strongly affects the structure of Earth's outer atmosphere.

Many questions about the Sun remain unanswered, such as why its outer atmosphere has a temperature of over a million Kelvin while its visible surface (the photosphere) has a temperature of just 6,000 K. Others include the exact diameter of the sun and it's distance above the earth's surface. Current topics of scientific inquiry include the sun's regular cycle of sunspot activity, the physics and origin of solar flares and prominences, the magnetic interaction between the chromosome and the corona, and the origin of the solar wind.

 The Solar System v·d·e 
Solar System XXVII
The Sun · Mercury · Venus · Earth · Mars · Ceres* · Jupiter · Saturn · Uranus · Neptune · Pluto* · Eris* · Sedna*
Planets · Dwarf planets · Moons: Terran · Martian · Asteroidal · Jovian · Saturnian · Uranian · Neptunian · Plutonian · Eridian
Pluto' * Ceres * Eris * Haumea * Makemake
Small bodies:   Meteoroids · Asteroids (Asteroid belt) · Centaurs · TNOs (Kuiper belt/Scattered disc) · Comets (Oort cloud)
planets with '*' are dwarf's but listed between 'real planets'.
See also astronomical objects and the solar system's list of objects, sorted by radius or mass.