What happens in the sun?

Answer 1

The question is a little broad to answer directly. I assume you want to know how the Sun gets to shine. This is due nuclear fusion being performed in the Sun's core. The pressure and temperature in said core are immense and high enough for hydrogen ions to fuse together to form helium. This process generates a large amount of energy (in the form of light and neutrinos) which heats up the Sun.

The Sun finally shines because it is hot. Radiation coming from the core does not immediately reach the surface, that takes a lot of time. Instead what we see is the thermal radiation coming from the hot surface.

Knowledge of these processes has been acquired from a number of ways; direct observations using telescopes (both in the optical and other spectra of light) and more recently neutrino observations. One can look for many things; emission and absorption spectra, sun spots, differential rotation etc. Also used are advances in the fields of nuclear and particle physics.

Answer 2

The Sun is a star that undergoes nuclear fusion in its core, converting hydrogen into helium. This process releases energy in the form of light and heat, which sustains life on Earth. Additionally, the Sun's intense magnetic activity drives solar flares and coronal mass ejections, which can affect space weather and impact technology on Earth.