Astronomy and cosmology

About this lab: Astronomy and cosmology

Interactive simulation for Cambridge A Level Physics 9702 topic 25 Astronomy and cosmology: a Cepheid, a type Ia supernova or a Sun-like star as a standard candle with the radiant flux intensity F = L/4πd² falling with distance, black-body curves for the Sun, Sirius, Betelgeuse, Rigel, Proxima and Vega with Wien's law for the surface temperature and Stefan-Boltzmann for the radius, and the redshift of a galaxy's spectral lines with Hubble's law v = H₀d, a Hubble plot of six clusters and the age of the universe from 1/H₀.

Standard candles and the inverse-square law, stellar temperatures and radii from Wien's and Stefan's laws, and Hubble's law with the expanding universe

Astronomy and cosmology is a free, browser-based simulation for Cambridge International AS & A Level Physics 9702 (topic 25 Astronomy and cosmology). The course is assessed in Paper 1 (multiple choice), Paper 2 (AS structured), Paper 3 (advanced practical), Paper 4 (A Level structured) and Paper 5 (planning, analysis and evaluation). There are 3 tabs, each a self-contained experiment with its own controls and live readings, and nothing to install: it runs on a laptop, tablet or classroom projector.

Syllabus coverage

• 25.1 Standard candles: Luminosity as total power radiated by a star; Inverse square law: F = L ÷ (4πd²); Standard candles and distance to galaxies. Lessons: Standard candles and the inverse square law.
• 25.2 Stellar radii: Wien's displacement law: λ_max ∝ 1 ÷ T; Stefan-Boltzmann law: L = 4πσr²T⁴; Estimating a star's radius from its luminosity and temperature. Lessons: Stellar radii: Wien and Stefan-Boltzmann.
• 25.3 Hubble's law and the Big Bang: Redshift of spectral lines from receding galaxies; Redshift relation: Δλ ÷ λ ≈ Δf ÷ f ≈ v ÷ c; Hubble's law: v = H₀d; The expanding Universe and the Big Bang theory; Age of the Universe estimated from 1 ÷ H₀. Lessons: Hubble's law and the Big Bang.

Full syllabus map: A Level Physics 9702 topic 25.

How to use this simulation

1. 1. Standard candles.
2. 2. Stellar radii.
3. 3. Hubble's law.
4. The buttons at the end of the tab strip give the scene the whole window (Full screen, Hide controls) and, on a dark stage, a projector-friendly palette (Light scene). Many scenes also have drag handles: drag them to change the set-up directly.

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