jansky¶

A hands-on radio astronomy course in Python.

In 1932, a young Bell Labs engineer named Karl Jansky was hunting for sources of static that interfered with transatlantic radio-telephone calls. He found a hiss that rose and set four minutes earlier each day — not with the Sun, but with the stars. He had discovered radio emission from the centre of the Milky Way, and with it, a brand-new window on the universe. The unit of radio brightness, the jansky (Jy), bears his name, and so does this course.

This is a self-guided tour from "what is a radio wave from space?" all the way to downloading real telescope data and doing original analysis. Every chapter is an executable Jupyter notebook that mixes prose, the physics (with equations), runnable code, and plots — and cites the seminal papers so you can read the originals.

How the course is organised¶

Part	Chapters	You will learn to…
I — Foundations	1–3	reason about radio emission, brightness temperature, noise, and the radiometer equation
II — Instrumentation	4–6	understand antennas & receivers, and (optionally) capture real signals with an SDR and detect the 21 cm hydrogen line
III — Interferometry	7–9	combine antennas into an interferometer, synthesise an aperture, and deconvolve images with CLEAN
IV — Real research	10–15	pull data from open archives (NRAO/VLA, HEASARC, HI surveys, SDSS/Gaia) and carry out real analyses, ending in a capstone project

Hardware chapters (5 & 6) are optional — clearly marked, with archival/simulated fallbacks so you can complete the whole course with nothing but a laptop.

The journey at a glance¶

flowchart TD
  subgraph I[Part I · Foundations]
    direction LR
    C1[1 · What is radio astronomy] --> C2[2 · Radio emission] --> C3[3 · Noise & radiometer]
  end
  subgraph II[Part II · Instrumentation]
    direction LR
    C4[4 · Antennas] --> C5[5 · SDR] --> C6[6 · Hydrogen line]
  end
  subgraph III[Part III · Interferometry]
    direction LR
    C7[7 · Why interferometry] --> C8[8 · Aperture synthesis] --> C9[9 · CLEAN]
  end
  subgraph IV[Part IV · Real research]
    direction LR
    C10[10 · Archives] --> C11[11 · HI rotation] --> C12[12 · VLA imaging] --> C13[13 · Pulsars] --> C14[14 · Multi-wavelength] --> C15[15 · Capstone]
  end
  I --> II --> III --> IV

That's the linear core (Chapters 1–15). The course actually has 36 chapters plus a Maths Lab — see Learning Paths for the full map, every chapter's prerequisites, and themed routes (laptop-only, RTL-SDR, interferometry, pulsars & transients, just the physics).

Prefer pictures to prose? Start with the Visual Tour — diagrams, plots, photographs, and videos for the whole course.

A taste of what's inside¶

Reproduce Jansky's discovery and Reber's first radio maps.
Fit a spectral index to separate thermal from synchrotron emission.
Watch a signal climb out of the noise as you "integrate down" — the radiometer equation in action.
Build a two-element interferometer, fill the uv-plane by Earth rotation, and run Högbom's CLEAN by hand.
Derive the Milky Way's rotation curve from HI 21 cm data — and meet the evidence for dark matter.
Dedisperse and fold a real pulsar; image a VLA field in CASA; cross-match radio sources with Gaia.

Get started¶

New here? Start Here helps you pick a track in a minute. Otherwise head straight to the Setup page to install the environment (local with uv, or via containers), then open Chapter 1. The References page collects the landmark papers and textbooks the course draws on.

Radio astronomy is one of the most welcoming corners of astrophysics for a programmer: the data are signals, the maths is Fourier transforms, and the tools are open source. Welcome aboard.