Sun

Quick facts

• The Sun (often called Sol) is a G‑type main‑sequence star (spectral class G2V) and is about 4.6 billion years old. ([science.nasa.gov](https://science.nasa.gov/universe/stars/types/?utm_source=openai))
• The Sun contains roughly 99.86% of the Solar System’s known mass (mass ≈ 1.988 × 10^30 kg) and has a diameter of about 1.39 million km (≈109 Earth diameters). ([solarsystem.nasa.gov](https://solarsystem.nasa.gov/sun-by-the-numbers/?utm_source=openai))
• The Sun’s total power output (luminosity) is about 3.828 × 10^26 watts; in its core hydrogen fuses to helium and the process converts roughly 4 million tons of mass into energy every second. ([iauarchive.eso.org](https://iauarchive.eso.org/static/resolutions/IAU2015_English.pdf?utm_source=openai))
• Earth’s average distance to the Sun is 1 astronomical unit (AU); the AU is defined exactly as 149,597,870,700 m, and sunlight takes about 8 minutes 19 seconds to travel from the Sun to Earth. ([publish.obsidian.md](https://publish.obsidian.md/spaceaudits/Sources/2012_IAU_Resolution_B2_AU_Redefinition?utm_source=openai))
• Only the Sun’s innermost region (a modest central fraction by mass and radius) is hot and dense enough for sustained fusion; the Sun is middle‑aged and is expected to remain on the main sequence for roughly another ~5 billion years before evolving into a red giant. ([spdf.gsfc.nasa.gov](https://spdf.gsfc.nasa.gov/pub/documents/old/websites/sunearthday.nasa.gov/2007/locations/ttt_solarenergy.php?utm_source=openai))