Here is a step-by-step breakdown of how new stars are formed:
1. Giant Molecular Clouds:
a) Stellar nurseries are characterized by the presence of giant molecular clouds (GMCs), which are vast and dense regions of interstellar gas and dust.
b) These GMCs are predominantly composed of molecular hydrogen (H2), along with trace amounts of other elements and compounds.
2. Gravitational Collapse:
a) Within a GMC, gravity plays a crucial role in initiating star formation. As the GMC's own gravity overcomes the opposing forces, such as thermal pressure, the cloud begins to collapse under its weight.
b) The contraction leads to an increase in density and pressure within the GMC.
3. Fragmentation:
a) As the GMC collapses, it fragments into smaller, denser clumps known as "cores" or "protostars."
b) These protostars are the initial seeds from which individual stars will eventually form.
4. Protostellar Disk:
a) As a protostar continues to collapse, it gathers more mass and angular momentum.
b) The protostar develops a surrounding disk of gas and dust, known as a protostellar disk, which rotates around the central protostar.
5. Protostellar Evolution:
a) The protostar at the center of the protostellar disk continues to accrete mass from the surrounding disk.
b) As the protostar accumulates more mass, its core temperature increases, leading to the initiation of nuclear fusion reactions.
6. Stellar Birth:
a) Once the protostar's core temperature reaches approximately 10 million Kelvin, nuclear fusion begins, marking the birth of a new star.
b) The outward pressure generated by nuclear fusion balances the inward pull of gravity, establishing hydrostatic equilibrium. The protostar transitions into a full-fledged star, emitting its own light and energy.
The formation of stars is an ongoing and dynamic process that occurs throughout the universe, contributing to the ever-changing tapestry of the cosmos.
