Astronomy
Stars
HR diagram, fusion, lifetimes, magnitude.
Basics
Hertzsprung–Russell diagram
X: temperature (hot on the left). Y: luminosity. The main sequence is the diagonal. Giants and supergiants sit above; white dwarfs below. Mass largely sets main-sequence place and lifetime.
Fusion
The Sun’s core: proton–proton chain, H → He. More massive stars use the CNO cycle. When hydrogen is gone, the star moves toward red giant, then white dwarf, neutron star, or black hole by mass.
Formulas
Wien's displacement law
Hotter stars peak at shorter (bluer) wavelengths.
Symbols
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λ_maxwavelength of peak emission
Stefan–Boltzmann
Luminosity scales as radius squared and T to the fourth. A cool, huge giant can still be bright.
Symbols
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Lluminosity (W) -
σStefan–Boltzmann constant
Apparent magnitude
Smaller magnitude is brighter. Five magnitudes = 100× flux.
Symbols
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Fflux
Distance modulus
Distance from apparent vs absolute magnitude.
Symbols
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Mabsolute magnitude (10 pc) -
ddistance
Parallax
A parallax of 1 arcsecond is 1 parsec. The basic nearby-star distance.
Symbols
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pparallax (arcseconds)
In this field
Solar system
Planets, Kepler, gravity, escape speed.
Galaxies and cosmology
Galaxies, Hubble, redshift, black holes.
Observing basics
Celestial sphere, coordinates, telescopes, spectra.
Exoplanets and life
Detection, habitable zone, a SETI sketch.
The Sun and space weather
Solar structure, spots, flares and CMEs.
Moon, tides, and eclipses
Lunar phases, tides, and solar and lunar eclipses.
Magnitudes and spectra
Apparent and absolute magnitude, distance modulus, colour and spectral type, Wien’s law.
Galaxies and Hubble
Galaxy shapes, rotation curves, the Hubble–Lemaître law, and a standard-candle sketch.
Telescopes and light
Aperture, diffraction limit, collecting area, seeing versus space telescopes.
Stellar death
Red giants, supernovae, and sketches of white dwarfs, neutron stars, and black holes.