  Even if it tends to hide more often in the current autumnal season, our host
star, the Sun, is the principal source of energy on our planet. It has a
luminosity of 3.828e26 Watts, and despite that we receive only 2 parts per
billion of this, it allows for the Earth's life to thrive. Moreover, we know
that the Sun has been shining in the same way for about 4.6 billion years (the
age of the Earth) and will likely still do the same for another 5 billion years
or so. The Sun's power engine, as well as the one of all the stars we see in
the night sky, has for long been a mystery, but astronomers now have a good
understanding of it.
