Lesson 04 Tier I · Foundations The Sun — Our Nearest Star Solar structure, nuclear fusion, the solar cycle, and space weather A Star Up Close The Sun is, in cosmic terms, a thoroughly ordinary star — a middle-aged, medium-mass, main-sequence star of spectral type G2V. And yet it is the only star we can […]
Lesson 03 Tier I · Foundations Gravity & Orbital Mechanics Newton, Kepler’s laws, orbital velocity, and escape velocity The Force That Shapes Everything Of the four fundamental forces in nature, gravity is by far the weakest — and by far the most consequential at astronomical scales. It is the architect of the cosmos: it collapses […]
Lesson 02 Tier I · Foundations Light — The Cosmic Messenger The electromagnetic spectrum, photons, the speed of light, and redshift Why Light Is Everything In astrophysics, we cannot reach out and touch the objects we study. We cannot bring a star into a laboratory. Almost everything we know about the universe — the temperature […]
Lesson 01 Tier I · Foundations The Scale of the Universe Size, distance, light-years, and the cosmic address system Introduction Before we can understand astrophysics, we must first understand where we are. The universe is so vast that our everyday intuitions about size and distance become completely useless. The first and most important skill in […]