Question: how hot is the sun and how do you measure the tempreture if people say it is as hot as they think?

Sharon Sneddon answered on 21 Mar 2011:

Hi Sterling122333,

It’s estimated that the core of the sun is 15,000,000°C. In other words pretty hot!! It’s thought that the outside of the sun is about 5505 °C
So how do scientists know this? I didn’t so I had to look it up!
One method, called Wien’s law, uses the wavelength of the peak emission, wavelengthpeak, in the Sun’s continuous spectrum. The temperature in Kelvin = 2.9 × 106 nanometers/wavelengthpeak.

Another method uses the flux of energy reaching the Earth and the inverse square law. Flux is the amount of energy passing through a unit area (e.g., 1 meter2) every second. From the inverse square law of light brightness, you find that the solar flux at the Earth’s distance = the Sun’s surface flux × (Sun’s radius/Earth’s distance)2 = 1380 Watts/meter2.

Since the Sun’s photosphere is approximately a thermal radiator, the flux of energy at its surface = sigma × (the Sun’s surface temperature)4, where sigma is the Stefan-Boltzmann constant. Rearranging the equation, the photosphere’s temperature = [(solar flux at Earth)/sigma) × (Earth distance/Sun’s radius)2]1/4.

These two methods give a rough temperature for the Sun of about 5800 K or 5505 °C. The upper layers of the photosphere are cooler and less dense than the deeper layers, so you see absorption lines in the solar spectrum. You can use the absorption line strengths as an accurate temperature probe to measure a temperature of about 5840 K.

If you understood all that then you are a better scientist than me! I think I’ll stick to biology!