The nebular hypothesis is the prevailing scientific theory for how the solar system formed. It proposes that the solar system originated from a giant, rotating cloud of gas and dust called a solar nebula. This nebula was composed primarily of hydrogen and helium, with trace amounts of heavier elements.

According to the nebular hypothesis, the nebula began to collapse under its gravity, causing it to spin faster and faster. As the nebula contracted, it began to heat up, and the heavier elements condensed into small, solid particles called planetesimals.

These planetesimals collided and stuck together, gradually forming larger and larger objects. Eventually, the largest of these objects became the planets, moons, and other bodies of the solar system. The Sun formed at the center of the nebula, from the remaining gas and dust.

The nebular hypothesis is supported by a number of observations, including:

* The composition of the Sun, planets, and other bodies of the solar system is similar to that of the Sun's atmosphere.

* The planets orbit the Sun in a flat, disk-shaped plane.

* The planets' orbits are nearly circular, and they all rotate in the same direction as the Sun.

* The solar system has a hierarchical structure, with the planets orbiting the Sun, the moons orbiting the planets, and so on.

The nebular hypothesis is not without its challenges, but it remains the best-supported explanation for how the solar system formed.