Ever wondered how hot, the Sun, our nearest star, is? After all, with its gigantic size, it provides heat for our entire Solar System.
With a radius of 696,342km, the bright ball of energy is large enough to fit over 1.3 million Earths inside. And with a core capable of thermonuclear reactions, it produces a staggering amount of heat.
How hot is the Sun?
The Sun is around 15 million °C (27 million °F) at its core and 5,500°C (9932°F) on its surface. The outer atmosphere surrounding the Sun measures around 2 million °C (3.6 million °F) with some areas of it reaching as hot as 20 million °C (36 million °F).
The core of our yellow dwarf star is hot enough for thermonuclear reactions to take place, but scientists are not too sure why the temperature of the solar atmosphere is so high. Some have proposed that energy travels through the Sun's magnetic field into its atmosphere where it 'explodes'.
NASA’s Parker Solar Probe is on a mission to discover why the corona (the atmosphere around the Sun) is so hot.
Why is the Sun so hot?
The Sun is so hot because the immense pressure in its core creates continual nuclear fusion. The heat, light, and energy created in its core via those thermonuclear reactions radiate outward onto the surface of the Sun, into its atmosphere, and out into space beyond.
Essentially, the Sun is a giant gas and plasma ball, with 92 per cent of the star’s gas made up of hydrogen. The immense gravity and pressure at its core make these hydrogen atoms collide and create helium. This is known as nuclear fusion. Nuclear fusion creates a huge amount of heat and energy, providing the heat for our Solar System.
Are there any stars hotter than the Sun?
The hottest known star is WR 102, found in the Sagittarius constellation, which has a surface temperature of over 200,000°C (360,032°F). This is over 36 times hotter than our Sun.
It’s not just WR 102 that’s hotter than the Sun, though, as there are plenty of stars out there that boast higher temperatures. Stars like WR 102, white dwarfs, and neutron stars can all be hotter.
How do scientists know the temperature of the Sun?
The temperature of the Sun is measured by theory backed up by solar missions, including the Parker Solar Probe. Scientists can measure the heat of the Sun by using remote telescopes that employ spectroscopic data.
Data collected from measuring the Sun’s photosphere, chromosphere, transition region, and corona can be used to inform scientists of the heat of the Sun’s core and outward through to its surface as we know of the thermonuclear fusion process of its centre. Essentially, the core temperature of the Sun has been figured out by maths, backed up by real-world data.
This real-world data is gathered by studying the Sun’s wavelengths. The colour of light that a star emits is used to garner its temperature, where the spectrograph comes in - which splits light “by a dispersive optical element into its different components (or wavelengths) in order to be studied,” as explained by ESA Hubble.
Read more:
