Exactly how much AU is the radius of the Sun?

About 1/93 AU.

Sun Radius

Radius Of Sun

Divide about 435,000 by approximately 93 million to get your answer in AU. To be more accurate than that you must consider the sun is a ball of gas, measured at 1,390,000 km diameter, but has no defined surface boundary, and the earth's orbit is elliptical, and the figure for AU is 149,597,871 km as used by astronomers. 1390000/2*149597871 is 0.00465 AU

The sun's radius is 0.004650 AU.

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ORBIT The earth's orbit is an ellipse, not a perfect circle. It therefore varies in distance from the sun, achieving perihelion (the nearest point to the sun) on or near January 4th every year and looping out to aphelion (the furthest distance from the Sun) on or about July 4th each year. The average distance from the Sun (about a fortnight after the spring equinox and the autumn equinox) is 93 million miles and the maximum and minimum are, as noted above, about 94.5 and 91,5 million miles. Light takes 8 minutes 19 seconds on average to get here but that too varies with the distance by as much as 17 seconds from aphelion to perihelion. TEMPERATURE 5785 Kelvin at the surface (photosphere) which is fairly typical for a G2 V star. Kelvins use the same size unit as Celsius degrees but the scale starts at Absolute Zero (-273 C) Temperature of outer atmosphere: >1 Mega Kelvin (1 Million Degrees Celsius) Temperature of corona: 5 Mega Kelvin Temperature of core: 13.6 Mega Kelvin THE SOLAR ATMOSPHERE The parts of the Sun above the photosphere are referred to collectively as the solar atmosphere. They can be viewed with telescopes operating across the electromagnetic spectrum, from radio through visible light to gamma rays, and comprise five principal zones: The temperature minimum, The chromosphere, The transition region, The corona, and The heliosphere. The heliosphere, which may be considered the tenuous outer atmosphere of the Sun, extends outward past the orbit of Pluto to the heliopause, where it forms a sharp shock front boundary with the interstellar medium. The chromosphere, transition region, and corona are much hotter than the surface of the Sun; the reason why is not yet known. The coolest layer of the Sun is a temperature minimum region about 500 km above the photosphere, with a temperature of about 4,000 K. This part of the Sun is cool enough to support simple molecules such as carbon monoxide and water, which can be detected by their absorption spectra. Above the temperature minimum layer is a thin layer about 2,000 km thick, dominated by a spectrum of emission and absorption lines. It is called the chromosphere from the Greek root chroma, meaning color, because the chromosphere is visible as a colored flash at the beginning and end of total eclipses of the Sun. The temperature in the chromosphere increases gradually with altitude, ranging up to around 100,000 K near the top. Above the chromosphere is a transition region in which the temperature rises rapidly from around 100,000 K to coronal temperatures closer to one million K. The increase is because of a phase transition as helium within the region becomes fully ionized by the high temperatures. The transition region does not occur at a well-defined altitude. Rather, it forms a kind of nimbus around chromospheric features such as spicules and filaments, and is in constant, chaotic motion. The transition region is not easily visible from Earth's surface, but is readily observable from space by instruments sensitive to the far ultraviolet portion of the spectrum. The corona is the extended outer atmosphere of the Sun, which is much larger in volume than the Sun itself. The corona merges smoothly with the solar wind that fills the solar system and heliosphere. The temperature of the corona is several million kelvin. While no complete theory yet exists to account for the temperature of the corona, at least some of its heat is known to be from magnetic reconnection. The heliosphere extends from approximately 20 solar radii (0.1 AU) to the outer fringes of the solar system. Its inner boundary is defined as the layer in which the flow of the solar wind becomes superalfvénic—that is, where the flow becomes faster than the speed of Alfvén waves. Turbulence and dynamic forces outside this boundary cannot affect the shape of the solar corona within, because the information can only travel at the speed of Alfvén waves. The solar wind travels outward continuously through the heliosphere, forming the solar magnetic field into a spiral shape, until it impacts the heliopause more than 50 AU from the Sun. In December 2004, the Voyager 1 probe passed through a shock front that is thought to be part of the heliopause. Both of the Voyager probes have recorded higher levels of energetic particles as they approach the boundary. THINK THAT'S HOT? IT WILL GET EVEN HOTTER! When the Sun enter a red giant phase in 4-5 billion years, its outer layers will expand as the hydrogen fuel in the core is consumed and the core will contract and heat up. Helium fusion will begin when the core temperature reaches around 100 MegaKelvin, and will produce carbon and oxygen.

It's about 0.01 AU.