prototähti

Prototähti, also known as a protostar, is a stage in the formation of a star. It is a dense, hot core of gas and dust that has not yet ignited nuclear fusion in its core. Prototähti is formed from a collapsing cloud of gas and dust, known as a molecular cloud, which is primarily composed of hydrogen and helium. As the cloud collapses under its own gravity, it heats up and forms a protostar at its center.

The protostar continues to accrete mass from the surrounding molecular cloud, growing larger and hotter over time. As it grows, the protostar's core becomes denser and hotter, eventually reaching temperatures and pressures high enough to initiate nuclear fusion. Once nuclear fusion begins, the protostar becomes a main-sequence star and begins its life on the Hertzsprung-Russell diagram.

The duration of the protostar stage varies depending on the mass of the protostar. For low-mass stars like our Sun, this stage can last for millions of years. For high-mass stars, the protostar stage can be much shorter, lasting only a few hundred thousand years. During this time, the protostar may undergo periods of increased brightness and variability, as it continues to accrete mass and heat up.

Prototähti is an important stage in the formation of stars, as it is during this stage that the initial conditions for star formation are set. The properties of the protostar, such as its mass and rotation, will determine many of the characteristics of the resulting star, including its lifespan and eventual fate.