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The result was a measured radius of 696,342 ± 65 kilometres (432,687 ± 40 miles). [4] Haberreiter, Schmutz & Kosovichev (2008) [1] determined the radius corresponding to the solar photosphere to be 695,660 ± 140 kilometres (432,263 ± 87 miles). This new value is consistent with helioseismic estimates; the same study showed that previous ...
Sunlight on the surface of Earth is attenuated by Earth's atmosphere, so that less power arrives at the surface (closer to 1,000 W/m 2) in clear conditions when the Sun is near the zenith. [100] Sunlight at the top of Earth's atmosphere is composed (by total energy) of about 50% infrared light, 40% visible light, and 10% ultraviolet light. [101]
Earth radius (denoted as R 🜨 or R E) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid (an oblate ellipsoid), the radius ranges from a maximum (equatorial radius, denoted a) of nearly 6,378 km (3,963 mi) to a minimum (polar radius, denoted b) of nearly 6,357 km (3,950 mi).
Its distance to the Sun varies annually between 147.1·10 6 km at perihelion and 152.1·10 6 km at aphelion. In addition, several long term (tens to hundreds of millennia) cycles of subtle variation in the Earth's orbit (Milankovich cycles) affect the solar irradiance and insolation (but not the solar constant).
In fact, under clear skies a solar panel placed horizontally at the north or south pole at midsummer receives more sunlight over 24 hours (cosine of angle of incidence equal to sin(23.5°) or about 0.40) than a horizontal panel at the equator at the equinox (average cosine equal to 1/ π or about 0.32).
This is because the distance between Earth and the Sun is not fixed (it varies between 0.983 289 8912 and 1.016 710 3335 au) and, when Earth is closer to the Sun , the Sun's gravitational field is stronger and Earth is moving faster along its orbital path. As the metre is defined in terms of the second and the speed of light is constant for all ...
The calculated stellar distance will be in the same measurement unit as used in Distance earth-sun (e.g. if Distance earth-sun = 1 au, unit for Distance star is in astronomical units; if Distance earth-sun = 1.5813 × 10 −5 ly, unit for Distance star is in light-years).
109 Gm (0.7 au) – distance between Venus and the Sun; 149.6 Gm (93.0 million mi; 1.0 au) – average distance between the Earth and the Sun – the original definition of the astronomical unit; 199 Gm (1.3 au) – diameter of Rho Persei, an asymptotic giant branch star, fusing carbon into neon in a shell surrounding an inert core. [179]