tähekujundus

Tähekujundus, also known as star formation, is the fundamental process by which dense regions within molecular clouds collapse under their own gravity to form stars. These molecular clouds are vast interstellar collections of gas, primarily hydrogen and helium, and dust. The process begins when a portion of a molecular cloud becomes gravitationally unstable, often triggered by external events such as supernova explosions or collisions with other clouds, which can cause compression and lead to gravitational collapse.

As the region collapses, it fragments into smaller clumps, each of which continues to condense. The gravitational potential energy of the collapsing gas is converted into thermal energy, causing the core of each clump to heat up. When the temperature and pressure in the core become high enough, nuclear fusion ignites, and a protostar is born. This protostar continues to accrete material from its surrounding envelope.

The formation of a star is often accompanied by the development of a circumstellar disk, a rotating disk of gas and dust from which planets may eventually form. Jets of material are also commonly ejected from the poles of the protostar. Eventually, the protostar sheds its outer layers and becomes a main-sequence star, where it will spend the majority of its life fusing hydrogen into helium in its core. The timescale for star formation varies depending on the mass of the star, but it can take millions of years for a star like our Sun to fully form.