säälin

Sólin (the Sun) is the star at the center of the Solar System and the primary source of light and heat for Earth. In Icelandic, sólin is the definite form of sól, the ordinary word for sun, used in everyday language as well as in scientific writing.

The Sun is a G-type main-sequence star (spectral type G2V) that formed about 4.6 billion years ago from a solar nebula. It has a diameter of about 1.39 million kilometers and a mass of roughly 1.989 × 10^30 kilograms, comprising about 74% hydrogen and 24% helium, with heavier elements making up the rest. Nuclear fusion in the core converts hydrogen into helium via the proton–proton chain, releasing energy that travels outward through the radiative and convective zones.

The visible surface, or photosphere, has a temperature around 5,500–5,800 K, giving the Sun its characteristic yellow-white color. Above lie the chromosphere and the corona, which are more easily observed during eclipses or with specialized instruments. The Sun shows magnetic activity that follows an approximately 11-year cycle, during which sunspots, solar flares, and coronal mass ejections become more or less frequent. The solar wind, a stream of charged particles, fills the heliosphere and influences space weather throughout the solar system.

The Sun’s gravity governs the orbits of the planets. Earth remains at an average distance of about 1 astronomical unit (AU). The solar system’s habitable zone is estimated to lie roughly between 0.95 and 1.37 AU, depending on planetary atmospheres and stellar activity.

In the long term, the Sun will exhaust its core hydrogen, expand into a red giant, and eventually shed its outer layers, ending life as a white dwarf several billion years from now.