The HR diagram, fusion, main sequence, giants, supernovae, white dwarfs, neutron stars and stellar nucleosynthesis.
39 cards · basic cards · AI-written, checked twice. Edit anything.
- What do the axes of the Hertzsprung-Russell diagram represent?
Show answer
Horizontal axis: stellar temperature or spectral type (increasing left to right). Vertical axis: luminosity or absolute magnitude (increasing upward).- Where does the main sequence appear on the HR diagram?
Show answer
A diagonal band running from upper-left (hot, luminous stars) to lower-right (cool, dim stars).- Where are red giants located on the HR diagram?
Show answer
Upper-right region: cool surface temperature but very high luminosity.- Where are white dwarfs located on the HR diagram?
Show answer
Lower-left region: very hot surface temperature but very low luminosity.- What is the turnoff point on an HR diagram?
Show answer
The point where stars leave the main sequence, indicating the age of a stellar population like a globular cluster.- Define the main sequence.
Show answer
A stable phase where a star fuses hydrogen to helium in its core, lasting the majority of the star's lifetime.- What fraction of a star's lifetime does it spend on the main sequence?
Show answer
Approximately 90 percent; it is the longest phase of stellar evolution.- Describe the mass-luminosity relation on the main sequence.
Show answer
Luminosity is proportional to approximately the 3.5th power of mass (L ∝ M^3.5), so massive stars are far more luminous than low-mass ones.- How do a star's color and surface temperature relate?
Show answer
Hotter stars are blue or white; cooler stars are red or orange. Color directly reflects temperature via Wien's displacement law.- How does stellar mass determine main sequence lifetime?
Show answer
Massive stars burn hydrogen much faster and have shorter lifespans; low-mass stars burn slowly and live for billions of years.- What is the proton-proton (pp) chain?
Show answer
A fusion pathway in which protons combine through several steps to form helium-4, releasing energy; dominant in low-mass stars like the Sun.- What is the CNO cycle?
Show answer
A fusion pathway where carbon, nitrogen, and oxygen nuclei catalyze the conversion of hydrogen to helium; dominant in high-mass stars.- In what type of stars does the CNO cycle dominate over the pp chain?
Show answer
High-mass stars with core temperatures above approximately 17 million Kelvin, where the CNO cycle is more efficient.- What triggers the formation of a red giant?
Show answer
Hydrogen fuel in the core is exhausted, hydrogen fusion moves to a shell, and the core contracts and heats, causing the envelope to expand.- What are the defining physical characteristics of a red giant?
Show answer
Very large radius, cool surface temperature (red color), and extremely high luminosity compared to main sequence stars of the same mass.
FlashKeepers