The Sun and Stellar Evolution

Vocabulary flashcards about the Sun and stellar evolution.

Hydrostatic Equilibrium

The balance between the forces of pressure and gravity in a star.

Nuclear Fusion

The process of combining atomic nuclei to release energy.

Proton-Proton Chain

The specific nuclear fusion process by which the Sun converts hydrogen into helium.

Neutrino

A nearly massless particle that interacts very weakly with matter.

Radiation

Energy transported by photons.

Convection

Energy transported by the movement of hot gas rising and cool gas falling.

Conduction

Energy transported by direct contact - not significant in the Sun.

Radiative Zone

The region of the Sun where energy is transported primarily by radiation.

Convective Zone

The region of the Sun where energy is transported primarily by convection.

Helioseismology

The study of the Sun's interior using surface waves.

Photosphere

The apparent surface of the Sun where light is emitted.

Limb Darkening

The optical effect where the edges of the photosphere appear less luminous.

Chromosphere

A layer of the Sun's atmosphere above the photosphere with a higher temperature.

Corona

The outermost layer of the Sun's atmosphere, characterized by very high temperatures.

Coronal Loops

Arcs of hot gas in the Sun's corona, confined by magnetic fields.

Coronal Holes

Regions in the Sun's corona that are cooler and less dense than their surroundings, associated with open magnetic field lines.

Solar Wind

A stream of charged particles flowing outward from the Sun.

Sunspots

Cooler, magnetically active regions on the Sun's surface.

Solar Maximum

The period of greatest solar activity in the solar cycle.

Solar Prominences

Tubes of gas arching above the Sun's surface, following magnetic field lines.

Solar Flares

Powerful eruptions of magnetic energy released on the Sun.

Coronal Mass Ejections

Bursts of energetic particles ejected from the Sun into the Solar System.

Stellar Mass

The most important determinant of a star's evolution.

Main Sequence

Stars that are fusing hydrogen to helium in their cores.

Luminosity

The total amount of energy a star radiates per unit time.

Mass-Luminosity Relationship

Luminosity is proportional to the mass raised to the power of 3.5.

Electron-Degenerate Matter

Extremely dense matter where electrons are packed tightly.

Red Giant

A large, cool, luminous star.

Hydrogen Shell Burning

Hydrogen fusion that occurs in a shell around a helium core.

Triple-Alpha Process

The fusion of three helium nuclei to form carbon.

Helium Flash

A brief, intense burst of helium fusion in the core of a low-mass star.

Horizontal Branch Star

A stage of stellar evolution where helium fuses to carbon in the core.

Asymptotic Giant Branch

A region of the H-R diagram occupied by stars with hydrogen and helium fusion in shells around a non-fusing carbon core.

Planetary Nebula

Ejected outer layers of a star.

White Dwarf

The leftover core of a star after it has ejected a planetary nebula.

Chandrasekhar Limit

The maximum possible mass for a stable white dwarf, about 1.4 solar masses.

Nova

A sudden increase in brightness of a star.

Supernova (Type Ia)

The explosion of a white dwarf that exceeds the Chandrasekhar limit.

G2 Star

A type of star, like the sun, based on its spectral class.

Solar Interior

The inner layers of the sun including the core, radiative zone, and convective zone.

Solar Activity

Dynamic phenomena on the sun including sunspots, flares, and coronal mass ejections.

Spectral Lines

Dark or bright lines in the spectrum of light from an object, used to identify the presence of certain elements.

Emission-line Spectrum

A spectrum of light that displays discrete bright lines rather than a continuum.

Absorption-line Spectrum

A spectrum of light that displays discrete dark lines rather than a continuum.

Fusion Reactions

Nuclear reactions where atomic nuclei combine releasing energy.

Electron Degeneracy

A quantum mechanical effect where electrons resist being compressed into smaller spaces.

Core Shrinking

The process where the core of a star collapses inward due to gravity.

H-R Diagram

A plot of stars showing luminosity versus temperature.

Stellar Wind

The outflow of gas from a star into space.

Torus

Ring shape of dust and gas around a star.

Binary Systems

A stellar system consisting of two stars orbiting around their center of mass.

Mass Transfer

The process where gas is transferred from one star to another across the Lagrangian point.

Umbra

The dark central region of a sunspot.

Penumbra

The lighter outer region of a sunspot.

Solar Dynamics Observatory (SDO)

A NASA mission monitoring the Sun's activity.

Asteroseismology

Using stellar oscillations to probe the interior of a star.

Stellar composition affects evolution

Minor factor in a star’s evolution

Cooler paths

Light travel through shallower path at edges of photosphere

Reddish Emission

Chromosphere gives off a reddish emission-line spectrum due to hydrogen

Voyager 1

connects to interstellar magnetic fields

Electric power grids disrupted

Solar storms can disrupt electric power grids and satellites and cause brilliant auroras.

Hertzsprung-Russell Diagram

Key to understanding stars

Protostar

Becomes a star when nuclear fusion begins.

Degenerate cinder

Cooling white dwarf