Key Concepts in Stellar Physics and Atomic Structure

Posted on Oct 31, 2025 in Chemistry

Fundamental Concepts in Astrophysics and Physics

Atom: The smallest unit of a chemical element, consisting of a nucleus containing protons and neutrons plus a surrounding cloud of electrons.
Nucleus: The central core of an atom, composed of protons and neutrons, carrying a net positive charge.
Proton: A positive atomic particle located in the nucleus of an atom.
Neutron: An atomic particle with no charge and approximately the same mass as a proton.
Electron: A low-mass atomic particle carrying a negative charge.
Isotope: A form of an atom with the same number of protons but a different number of neutrons.
Molecule: Two or more atoms chemically bonded together.
Density: Mass per unit volume.

Coulomb Force: The force of repulsion or attraction between positively and negatively charged bodies.
Ion: An atom that has lost or gained one or more electrons, resulting in a net electrical charge.
Ionization: The process in which atoms lose or gain electrons.
Binding Energy: The energy required to pull an electron away from its atom.
Quantum Mechanics: The study of the behavior of atoms and atomic particles.
Permitted Orbit: One of the unique orbits that an electron may occupy within an atom.
Energy Levels: One of a number of discrete states an electron may occupy in an atom.
Excited Atom: An atom in which an electron has moved from a lower to a higher energy level.
Ground State: The lowest permitted electron energy level in an atom.
Quantum Jump: The instantaneous transition of electrons from one orbit or energy state to another.

Heat: Energy contained in matter in the form of agitation of its constituent particles.
Temperature: A measure of the agitation among the atoms and molecules of a material.
Kelvin Temperature Scale: A temperature scale using Celsius degrees, where 0 K represents absolute zero.
Absolute Zero: The lowest possible temperature at which a material contains no extractable heat energy.
Blackbody Radiation: The spectrum of radiation emitted by a perfect radiator.
Wavelength of Maximum Intensity: The specific wavelength at which a radiating object emits the maximum amount of energy.
Wien’s Law: States that the hotter a glowing object is, the shorter its wavelength of maximum intensity will be; this wavelength is inversely proportional to its temperature.
Stefan-Boltzmann Law: States that hotter objects emit significantly more total energy than cooler objects of the same size.

Spectral Line: A sharp change in the spectrum produced by the absorption or emission of light by atoms.
Absorption Spectrum: A spectrum that results when continuous radiation passes through a cool gas.
Emission Spectrum: A spectrum produced by photons emitted by an excited gas.

Parallax: The apparent shift of an object relative to the background due to a change in the observer’s position.
Doppler Effect: The change in the wavelength of radiation due to the relative radial motion of the source and the observer.
Radial Velocity (V): The component of an object’s velocity directed away from or toward the observer.
Blueshift: A Doppler shift toward shorter wavelengths, caused by the velocity of approach (the source is moving toward the observer).
Redshift: A Doppler shift toward longer wavelengths, caused by a velocity of recession (the source is moving away from the observer).

Transits of Venus: An astronomical event occurring when Venus can be seen passing directly between the Sun and Earth.
Photosphere: The bright, visible surface of the Sun.
Sunspot: A dark spot on the Sun containing intense magnetic fields.; Conclusion: Based on Wien’s and Stefan-Boltzmann’s laws, sunspots are demonstrably cooler than the surrounding photosphere.
Granulation: The fine structure of bright grains with dark edges covering the Sun’s surface. These features typically last 10 to 20 minutes before fading away.
Convection: Circulation in a fluid driven by heat, where hot material rises and cool material sinks.
Chromosphere: The layer of bright gases situated just above the Sun’s photosphere.
Corona: The faint, outer atmosphere of the Sun, composed of low-density, high-temperature gas.
Filtergram: A photograph (usually of the Sun) taken specifically in the light of a narrow, defined region of the spectrum.