Pre-main-sequence stars
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| Pre-main-sequence stars | |
|---|---|
| Name | Pre-main-sequence stars |
| Type | Stellar evolutionary phase |
| Mass range | ~0.08–10+ M☉ |
| Notable examples | T Tauri stars, Herbig Ae/Be stars |
Pre-main-sequence stars are young stellar objects in the contracting phase before sustained hydrogen fusion in their cores. These objects bridge the collapse of molecular cloud cores in regions like the Orion Nebula and the onset of main-sequence life seen in associations such as the Pleiades and the Hyades. Studies of pre-main-sequence objects involve observations from facilities like the Hubble Space Telescope, the Spitzer Space Telescope, the Chandra X-ray Observatory, and theoretical work by groups at institutions including the Max Planck Institute for Astronomy, the Harvard-Smithsonian Center for Astrophysics, and the European Southern Observatory.
Introduction
Pre-main-sequence stars appear in star-forming regions such as the Orion Molecular Cloud Complex, the Taurus Molecular Cloud, and the Rho Ophiuchi cloud complex, and are typified by classes like T Tauri and Herbig Ae/Be identified historically by observers including Alfred H. Joy and George Herbig. Characterized observationally in studies by teams at the Institute for Astronomy, University of Hawaii, the California Institute of Technology, and the Jet Propulsion Laboratory, these objects inform models developed by researchers at the University of Cambridge Astronomy Department and the Princeton University Department of Astrophysical Sciences.
Formation and evolution
Pre-main-sequence stars form from gravitational collapse in molecular clouds traced by surveys from the James Clerk Maxwell Telescope and the Atacama Large Millimeter/submillimeter Array. Collapse and subsequent evolution follow frameworks proposed by theorists like Chandrasekhar, Eddington, and Hayashi, and are modeled in computational codes developed at the National Center for Supercomputing Applications and the Lawrence Berkeley National Laboratory. Observational constraints come from work by teams operating the Subaru Telescope, the Very Large Telescope, and missions such as Gaia that map young stellar kinematics in clusters studied by the Royal Astronomical Society and the American Astronomical Society.
Classification and observational properties
Classification schemes distinguish classical and weak-lined T Tauri stars described in catalogs compiled by observatories like the Kitt Peak National Observatory and papers from researchers at the University of Leiden. Spectral types and variability tie into atlases maintained at the Smithsonian Astrophysical Observatory and the Royal Observatory Edinburgh. Photometry from surveys by the Sloan Digital Sky Survey, the Two Micron All Sky Survey, and the Wide-field Infrared Survey Explorer complements spectroscopy from instruments at the Keck Observatory and the Gemini Observatory. Historic studies by figures such as Antonia Maury and Annie Jump Cannon influenced classification approaches still used by groups at the Carnegie Institution for Science.
Internal structure and energy sources
The internal structure of pre-main-sequence stars—convective envelopes, radiative cores, deuterium burning—was elaborated in work building on theories by Sir Arthur Eddington and later refinements by teams at the Max Planck Institute for Astrophysics and the Kavli Institute for Theoretical Physics. Energy sources include gravitational contraction described by solutions developed at the Institute for Advanced Study and brief nuclear burning stages explored in models from the Centre National de la Recherche Scientifique. Numerical simulations by groups at the Massachusetts Institute of Technology and the University of California, Berkeley probe convection and rotation, while asteroseismic constraints come from missions like Kepler and analysis by the European Space Agency teams.
Circumstellar material and accretion
Circumstellar disks around pre-main-sequence stars are sites of planet formation studied by observers at the National Radio Astronomy Observatory and theorists at the Max Planck Institute for Extraterrestrial Physics. Accretion signatures—emission lines, veiling, jets—have been catalogued by research groups at the Observatoire de Paris and the University of Arizona. High-resolution imaging from the Hubble Space Telescope and interferometry at the Very Large Telescope Interferometer reveal structures analyzed in collaboration with the Space Telescope Science Institute and the Laboratoire d'Astrophysique de Grenoble.
Role in stellar populations and clusters
Pre-main-sequence stars define the age sequences and initial mass functions measured in clusters like the Orion Nebula Cluster, the Chamaeleon I cloud, and the NGC 2264 region, with surveys conducted by the European Southern Observatory and the National Optical Astronomy Observatory. Their populations inform galaxy-scale star formation studies pursued by teams at the Max Planck Institute for Astronomy and the Harvard-Smithsonian Center for Astrophysics, and are central to debates at conferences of the International Astronomical Union and publications from the Astrophysical Journal.
Theoretical models and uncertainties
Theoretical models of pre-main-sequence evolution are developed using input physics from groups at the Los Alamos National Laboratory and the Argonne National Laboratory, with comparative model grids produced by the Baraffe group and collaborators at the Observatoire de Genève. Major uncertainties involve convection treatments, magnetic activity studied by researchers at the Institute of Space and Astronautical Science, and disk-star interactions investigated by teams at the University of Cambridge and the University of Colorado Boulder. Workshops and symposia at the Royal Society and the American Physical Society continue to refine opacities, equation-of-state inputs, and rotation physics underpinning evolutionary tracks used by the International Astronomical Union working groups.