The fact that the main sequence stars are represented by a band across the HR diagram that is smoothly populated from the rare O and B stars to the very common M stars strongly suggests that these stars are physically the same type of object, though some factor must be responsible for their range in observable properties. The Sun is a main sequence star and thus, by implication, all other main sequence stars must share its fundamental nature. Through theoretical modeling of the Sun and other main sequence stars, scientists have determined that the factor that differentiates them from the three other types of stars is the fact that their energy is generated internally by the conversion of hydrogen to helium (giants and supergiants produce their energy by gravitational contraction and by converting helium to even heavier elements; white dwarfs are like dying embers in a fireplace, radiating away their store of heat energy). Like most other stars, they also are in a state of equilibrium in which gravity is balanced by gas pressure at each radius, and the luminosity flowing outwards at each level is balanced by the energy generated interior to that level.
Astronomy
- A Brief History of Astronomy
- The Science of Astronomy
- Observing the Sky
- The Solar System
- Earth and its Moon
- Other Planets of the Solar System
- The Sun a Representative Star
- Observational Properties of Stars
- The Hertzsprung-Russell Diagram
- The Structure of Stars
- Formation and Evolution of Stars
- Final End States of Stars
- The Milky Way Galaxy
- Galaxies
- The Universe
- Life in the Universe
Main Sequence Stars
- Archaeoastronomy
- Greek Astronomy
- Foundations of Modern Astronomy
- Astronomy Defined
- Measurement Methods
- Basic Physics
- Electromagnetic Radiation (Light)
- The Scientific Method
- Naked-Eye Astronomy
- Telescopes and Observatories
- Introduction to the Solar System
- Origin and Evolution of the Solar System
- Terrestrial Planets, Gas‐Giant Planets
- Comparative Planetology: Terrestrials
- Comparative Planetology: Gas Giants
- Minor Objects: Asteroids, Comets, and More
- Other Planetary Systems
- Earth's Atmosphere
- Earth's Chemical Composition
- Interior Structure: Core, Mantle, Crust
- The Age of Earth
- Origin of the Earth‐Moon System
- Properties of Earth and the Moon
- Tidal Forces
- Evolution of the Earth‐Moon System
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
- Mercury
- Pluto
- Venus
- The Chromosphere
- The Corona
- The Sunspot Cycle
- Internal Structure; Standard Solar Model
- Energy Generation: Proton‐Proton Cycle
- Properties of the Sun
- Solar Neutrino Problem
- The Photosphere
- Helioseismology
- Stellar Parallax and Distances
- Apparent Magnitudes
- Absolute Magnitudes
- Luminosities
- Masses
- Radii
- Three Types of Astronomical Study
- Colors
- Spectral Types
- Surface Temperature
- Chemical Composition
- Luminosity Classes
- Proper Motions and Radial Velocities
- Properties of Secondary Importance
- Spectroscopic Parallax
- Hertzsprung Russell Diagram The Basics
- Main Sequence Stars
- Mass Luminosity Relationship
- Red Giants and Supergiants
- White Dwarf Stars
- Energy Generation The CNO Cycle
- Opacity
- Energy Transport
- High‐Mass Stars versus Low‐Mass Stars
- Other Types of Stars
- Equation of State
- Hydrostatic Equilibrium
- Thermal Equilibrium
- Evolution of Stars
- Formation of Stars
- Novae
- Type I Supernovae
- Type II Supernovae
- Neutron Stars (Pulsars)
- Black Holes and Binary X Ray Sources
- White Dwarf Stars
- Origin and Evolution of the Galaxy
- Interstellar Matter
- Interstellar Nebulae
- Star Clusters
- Structure of the Galaxy
- Clusters of Galaxies
- The Origin and Evolution of Galaxies
- Galaxies Types and Classifications
- Peculiar Galaxies
- Beyond the Big Bang Theory
- Observational Cosmology
- The Big Bang Theory
- Philosophical Considerations
- SETI—The Search for Extraterrestrial Intelligence
- Historical Background
- Scientific Considerations
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