Image: Y. Beletsky (LCO)/ESOHow to start learning astrophysics in high school
You can work out the mass of the Sun with high school algebra. Take the length of the year, \(3.16 \times 10^{7}\) seconds, and the radius of the Earth's orbit, \(1.50 \times 10^{11}\) m, put them into Newton's version of Kepler's third law, and out comes \(1.99 \times 10^{30}\) kg. Astrophysics is physics applied to objects nobody can touch, and a large part of it is within reach long before university.
Get the mathematics in order first
Four tools carry most of introductory astrophysics. Powers of ten and scientific notation come first, because the numbers are absurd: the Sun's luminosity is \(3.83 \times 10^{26}\) W and a hydrogen atom has a mass of \(1.67 \times 10^{-27}\) kg. Logarithms are needed for the magnitude scale that astronomers use for brightness. Trigonometry with small angles gives you distances and sizes. And you must be able to rearrange an equation without fear, including ones with squares, cubes and roots.
Practice estimating. How many stars would it take to match the mass of the Milky Way's central black hole? How long would light need to cross the solar system? A physicist checks every result against a rough guess, and that habit is worth more than any single formula.
Calculus matters later. If your school offers it, take it. Derivatives and integrals turn up as soon as you want to know how a star holds itself up or how the universe expands, and a university physics degree assumes them from the first week.
Learn physics before anything with "astro" in the name
Stars and galaxies obey the same laws as carts and pendulums. The school topics that matter most are mechanics (Newton's laws, energy, circular motion, gravitation), waves and light, heat and gases, and the basic structure of the atom. A student who really understands why a satellite stays in orbit is better prepared than one who can recite the spectral classes.
Take the hardest physics and mathematics courses your school offers. University admission to physics and astronomy programs is decided mainly on those grades.
Books and courses that work
Start with a survey. The free textbook Astronomy from OpenStax (second edition, by Fraknoi, Morrison and Wolff) covers the whole field with almost no mathematics and can be read online. It tells you what exists and which parts you find exciting.
The next step is a text that calculates. Ryden and Peterson's Foundations of Astrophysics is written for first and second year university students. The classic reference is Carroll and Ostlie's An Introduction to Modern Astrophysics, which runs to well over a thousand pages and uses calculus throughout. Nobody reads it cover to cover at 16. Borrow it from a library, pick one chapter on a topic you already know from the survey, and work through its examples with pencil and paper. If you want a list of formulas to aim for, see ten equations every astronomy student should know.
Popular science books and videos are good for motivation. They do not replace solving problems, and you will notice the difference the first time you sit in front of an exercise and have to decide which equation applies.
Work with real data and the real sky
Professional astronomical data are public to a degree that surprises newcomers. The Gaia archive of the European Space Agency holds positions, distances and brightnesses for 1.8 billion stars. The NASA Exoplanet Archive lists more than 6,000 confirmed planets with their masses, radii and orbital periods. Both can be downloaded as tables.
To use them you need a little programming. Python is the working language of astronomy, and the free libraries NumPy, Matplotlib and Astropy cover nearly everything a beginner needs. Two first projects that teach a lot:
- Download the Gaia stars within 100 parsecs and plot absolute magnitude against color. The result is a Hertzsprung-Russell diagram, with the main sequence, the giants and the white dwarfs made from real measurements.
- Plot exoplanet mass against orbital period and find the hot Jupiters, the giant planets with periods of a few days that nobody expected before 1995.
Look up as well. With 10×50 binoculars you can follow the four large moons of Jupiter from night to night. Io needs 1.77 days for one orbit at a distance of 421,700 km from the planet. You can time the period yourself. Put the two numbers into Kepler's third law and you get \(1.90 \times 10^{27}\) kg for the mass of Jupiter. The free planetarium program Stellarium tells you what is up tonight.
Citizen science is another way in. On the Zooniverse platform, volunteers classify galaxy shapes in Galaxy Zoo and search for planets in data from NASA's TESS satellite, and some have ended up as coauthors of published papers.
Competitions, clubs and a plan for one year
The International Olympiad on Astronomy and Astrophysics is the main competition for high school students. The 2025 olympiad in Mumbai had teams from 64 countries, and the 2026 edition was hosted by Hanoi. Each country selects its team through national rounds, and the published syllabus is a good study guide even if you never compete. Local astronomy clubs and the public nights of university observatories are where you meet people who can answer questions.
A workable plan for twelve months looks like this:
- Months 1 to 3: read a survey text and fix any gaps in algebra, logarithms and trigonometry.
- Months 4 to 6: learn enough Python to load a table and make a plot, and do one small data project.
- Months 7 to 9: work through the mechanics and light chapters of a calculating textbook, with the exercises.
- Months 10 to 12: pick one topic, such as exoplanets or black holes, and try your first research paper with the help of this guide to reading papers.
Three or four hours a week is enough if they are regular. If you are wondering where all this can lead, there is a separate article on what you can do with an astronomy degree.
The A&A Masterclass was written for readers in this position. Unit 1, The Astronomer's Toolkit, starts with powers of ten, logarithms, angles and Newton's laws, and Units 1 to 8 need only algebra, trigonometry and logarithms. Later units introduce simple derivatives and integrals and explain each step in words. The program page describes how the units, quizzes and the final exam fit together.
