What's inside a star?

Solar prominence
Credit: NASA, Goddard Space Center

A star’s energy is created in its core, and is radiated into space from its surface. In between, the energy is transported by various means. Gas constantly leaks away from its surface into space as stellar wind.

Structure of the Sun
Credit: Kelvinsong
Helioseismology
Digging deep: By studying pressure waves on the Sun, astronomers learn about the interior of a star. This method is called helioseismology
Credit: ESO/L. Calçada
Red onion
Red onion: The core of a red giant is a bit like an onion, with different layers of elements, each of which was produced at an earlier stage of the star’s life.
Credit: Pearson Education

Deep inside the Sun, energy from the core is transported by radiation (the radiative zone). In the outer layers, the convective motion of gas transports heat to the glowing surface; this is known as the convection zone. Other stars have different internal structures. In red dwarfs and red giants, the convection zone is much thicker, relatively speaking; in blue giants the radiative zone lies outside the convection zone. Energetic flares, dark sunspots, subsurface gas flows and solar wind are all governed by ever-changing magnetic fields.

Structural variety
Structural variety: Different stars have different internal structures, depending on their mass and core temperature.
Credit: Fahad Sulehria (www.novacelestia.com)

What would you see if you could look inside the Sun? Very hot gas in the centre, and a layer of "boiling" gas closer to the surface. Magnetic fields tell the gas particles how to move. They also create sunspots.