Phases of a star
Pro Research Analysisby 
Searched over 200M research papers
Phases of a Star: An Overview
Understanding the life cycle of stars involves exploring various phases from their formation to their ultimate fate. This article synthesizes recent research on the different phases of star formation and evolution, focusing on high-mass stars, star-forming regions, and unique stellar phenomena.
Early Phases of Star Formation
Embedded Phase of Star Formation
The earliest stages of star formation occur when young stars are still deeply embedded in their natal molecular clouds. This phase is critical in the matter cycle between gas clouds and young stellar regions. High-resolution infrared observations, such as those from the James Webb Space Telescope (JWST), have enabled the characterization of this heavily obscured phase. For instance, in the galaxy NGC 628, young massive stars remain embedded for approximately 5.1 million years, with about 2.3 million years being heavily obscured2.
Prestellar and Protostellar Phases
High-mass stars form within dense molecular regions (DMRs) and evolve through several stages. The prestellar phase involves the formation of dense cores within molecular clouds, which are often detected through far-infrared observations. These cores are typically cold and massive, with temperatures around 20 K and masses spanning several orders of magnitude3. The protostellar phase follows, where the core collapses to form a protostar, emitting primarily in the far-infrared3.
Accretion and Evolutionary Timescales
Accretion Phase
During the accretion phase, the protostar gains mass from its surrounding envelope. In magnetically-dominated clouds, this phase is characterized by significant magnetic braking, which reduces the angular momentum of the cloud core. This can lead to unique outcomes such as counter-rotating disks and weak outflows7.
Evolutionary Timescales
The formation process of high-mass stars is rapid and deeply embedded, making it challenging to observe. However, by modeling the chemical evolution of massive clumps, researchers have derived accurate timescales for different evolutionary phases. The total formation time for massive stars is approximately 520,000 years, with distinct phases such as the 70-μm weak phase lasting around 50,000 years and the HII-region phase lasting about 110,000 years5.
Phase Transitions and Unique Stellar Phenomena
Axion Stars
Axion stars, interpreted as self-gravitating Bose-Einstein condensates, exhibit phase transitions between dilute and dense states. These transitions are influenced by the self-interaction potential of the axions. A critical point exists above which a first-order phase transition occurs, leading to the formation of dense axion stars or black holes4.
Compact Stars and Quark Matter
Compact stars, such as neutron stars, may contain quark matter in their interiors. These stars can undergo sequential phase transitions from nuclear matter to different quark-matter phases, such as the two-flavor color-superconducting (2SC) phase and the color-flavor-locked (CFL) phase. This can result in multiple branches of hybrid stars with varying densities and radii6.
Conclusion
The phases of star formation and evolution encompass a wide range of phenomena, from the deeply embedded early stages to the complex transitions in compact stars. Advances in observational technology and theoretical modeling continue to enhance our understanding of these processes, providing insights into the life cycle of stars across different environments and conditions.
Sources and full results
Most relevant research papers on this topic
Phase Diagram of Star Polymer Solutions
Star polymer solutions in a good solvent can form fluids, crystals, and reentrant melting and freezing transitions, with stable phases including fluids, crystals, and reentrant melting and freezing transitions.
Highly CitedPHANGS–JWST First Results: Duration of the Early Phase of Massive Star Formation in NGC 628
The James Webb Space Telescope has enabled a more comprehensive study of the early phases of star formation in nearby galaxies, revealing that young massive stars remain embedded in their natal clouds for 5.1+2.7 Myr.
The Earliest Phases of Star Formation (EPoS): a Herschel key program - The precursors to high-mass stars and clusters
Cores with a 24°m counterpart are more advanced in their evolution, likely due to central protostar(s) heating the outer bulk of the core.
Highly CitedPhase transitions between dilute and dense axion stars
Self-gravitating axions can form stable dilute axion stars, collapse into dense axion stars, and collapse into black holes, with a triple point separating dilute, dense, and black hole states.
Highly CitedEstablishing the evolutionary timescales of the massive star formation process through chemistry
Our model accurately estimates the duration of individual phases of the high-mass star formation process using molecular tracers as chemical clocks.
Compact Stars with Sequential QCD Phase Transitions.
Compact stars with sequential QCD phase transitions can create a new family of denser compact stars, potentially leading to twin hybrid stars and triplets with the same mass but different radii.
Highly CitedDifferent modes of star formation – II. Gas accretion phase of initially subcritical star-forming clouds
Star formation in magnetically-dominated clouds with an initial subcritical mass-to-flux ratio can result in unique outcomes, such as counter-rotating disks, tiny disks, or direct collapse.
The Lifetimes of Phases in High-mass Star-forming Regions
The majority of high-mass star-forming regions are in a starless or embedded phase, with star-forming phases occupying 30%- 40% of their lifetimes.
A Census of Early-phase High-mass Star Formation in the Central Molecular Zone
High-mass star formation in the Central Molecular Zone is currently taking place in seven isolated clouds, suggesting that the next burst of star formation in the CMZ has not yet begun.
The earliest phases of high-mass star formation: a 3 square degree millimeter continuum mapping of Cygnus X
Our study of Cygnus X reveals that the infrared-quiet protostellar phase of high-mass stars may last as long as their better-known high-luminosity infrared phase.
Highly Cited