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Topic 13: Exploring starlight

3 dot points across 3 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do astronomers measure the distance to a star using its tiny shift or its pulsing brightness?

Arcminutes and arcseconds, the parsec, heliocentric parallax for measuring distances, and using Cepheid variables and other variable stars and their light curves.
A focused answer to Edexcel GCSE Astronomy statements 13.10 to 13.12 and 13.14 to 13.18, covering arcminutes and arcseconds, the definition of the parsec, measuring astronomical distances using heliocentric parallax, the light curves of variable stars, and using Cepheid variables as standard candles to find distances.
11 min answer →

What can a star's light tell us, and how does the Hertzsprung-Russell diagram organise the stars?

The information in a stellar spectrum, classifying stars by spectral type and colour, and sketching and reading the Hertzsprung-Russell diagram.
A focused answer to Edexcel GCSE Astronomy statements 13.4 to 13.8 and 13.13, covering the information obtained from a stellar spectrum, how stars are classified by spectral type and how colour and spectral type relate to surface temperature, and how to sketch and use the Hertzsprung-Russell diagram to follow a star's life cycle and find distances.
11 min answer →

How do astronomers measure how bright a star looks and how bright it really is?

The astronomical magnitude scale, apparent and absolute magnitude, the distance modulus formula, and the inverse square relationship between distance and brightness.
A focused answer to Edexcel GCSE Astronomy statements 13.1 to 13.3 and 13.9, covering the astronomical magnitude scale, how apparent magnitude relates to brightness as seen from Earth, absolute magnitude, the distance modulus formula M = m + 5 - 5 log d, and the inverse square relationship between distance and brightness.
11 min answer →