Astronomical unit
Videos
The astronomical unit is a unit of length defined as 149597870700 m. Historically, the astronomical unit was conceived as the average Earth-Sun distance, before its modern redefinition in 2012.
Transits of Venus across the face of the Sun were, for a long time, the best method of measuring the astronomical unit, despite the difficulties (here, the so-called "black drop effect") and the rarity of observations.
Sun
Videos
The Sun is the star located at the centre of the Solar System. It is a massive sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surf
Astronomical unit
…Lunar distance 0.0026 — Average distance from Earth (which the Apollo missions took about 3 days to travel) — Solar radius 0.005 — Radius of the Sun (695500 km, 432450 mi, a hundred times the radius of Earth or ten times the average radius of Jupiter) — Light-minute 0.12 — Distance light travels in…
The Sun as viewed through a clear solar filter
The photosphere is structured by convection cells referred to as granules.
The Sun's transition region taken by Hinode's Solar Optical Telescope
During a total solar eclipse the solar corona can be seen with the naked eye.