How long does it take for a star to form
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Star Formation Timescales: How Long Does It Take for a Star to Form?
Understanding the timescales involved in star formation is crucial for astrophysics. The process varies significantly depending on the type of star and the conditions within the molecular clouds where stars are born. This article synthesizes findings from multiple research studies to provide a comprehensive overview of the duration of star formation.
Formation of Sun-like Stars
For Sun-like stars, the formation process begins with the collapse of a gas and dust cloud under gravity. This process, from the initial collapse to the star shining like the Sun, takes approximately one million years . The leftover material from the star's birth often forms planets and other objects that orbit the new star.
Formation of Massive Stars
Massive stars, those with masses greater than 8-10 solar masses, form and evolve much more quickly than their lower-mass counterparts. The entire formation process for these stars is deeply embedded in their parental clumps, making observation challenging. The total formation time for a massive star is estimated to be around 520,000 years . This period is broken down into several phases:
- 70-μm weak phase: ~50,000 years
- Mid-IR weak phase: ~120,000 years
- Mid-IR bright phase: ~240,000 years
- HII-region phase: ~110,000 years
Star Formation in Clusters
Star clusters, which often contain both low and high-mass stars, form over several million years. Observations of regions like the Orion Nebula Cluster suggest that cluster formation can take several million years, spanning many local dynamical timescales 68. This extended timescale is consistent with the expected star formation rate in turbulent gas environments.
Molecular Clouds and Star Formation Efficiency
The efficiency and timescale of star formation are also influenced by the dynamics within molecular clouds. Studies show that star formation occurs in one or two crossing times for a range of scales, implying a rapid process relative to the cloud's dynamical timescale . For instance, in the nearby flocculent spiral galaxy NGC 300, molecular clouds are quickly dispersed by stellar feedback, limiting their lifetimes to about 10 million years and resulting in low star formation efficiencies of 2-3% .
High-Mass Star-Forming Regions
High-mass star-forming regions exhibit a dynamic and relatively quick formation process. The starless phase, where no stars are yet visible, occupies about 60-70% of the dense molecular region's lifetime, while the star-forming phase takes up the remaining 30-40% . The absolute lifetime of the starless phase is estimated to be between 0.2 to 1.7 million years, and the star-forming phase lasts about 0.1 to 0.7 million years.
Conclusion
The timescale for star formation varies significantly depending on the mass of the star and the conditions within the molecular clouds. Sun-like stars take about a million years to form, while massive stars can form in approximately 520,000 years. Star clusters and high-mass star-forming regions exhibit more complex and extended formation timescales, influenced by the dynamics of their environments. Understanding these timescales is essential for comprehending the broader processes of galaxy formation and evolution.
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