Astronomy

Exoplanets and life

Detection, habitable zone, a SETI sketch.

Basics

Detection

Transit: the star dims periodically — radius. Radial velocity: the star wobbles — minimum mass. Direct imaging is rare and contrast-hard. Atmospheric spectra can show molecular traces.

Habitable zone

Distances where liquid water could sit on a surface. It shifts with stellar luminosity and atmosphere. Necessary for life as we know it, not sufficient.

Formulas

Transit depth

ΔF / F ≈ (R_p / R_⋆)²

Planet radius over star radius. Earth/Sun is about 10⁻⁴.

Symbols

R_p planet radius
R_⋆ stellar radius

In this field

Solar system

Planets, Kepler, gravity, escape speed.

Stars

HR diagram, fusion, lifetimes, magnitude.

Galaxies and cosmology

Galaxies, Hubble, redshift, black holes.

Observing basics

Celestial sphere, coordinates, telescopes, spectra.

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.