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PX144 Introduction to Astronomy

Lecturer: Pier-Emmanuel Tremblay

Weighting 6 CATS

The Universe contains a bewildering variety of objects, from black-holes, red giants and white dwarfs to brown dwarfs, gamma-ray bursts and globular clusters, to name but a few. The module introduces this zoo, and, above all, shows how, from the application of physics, we have come to know their distances, sizes, masses and natures. The module starts with the Sun and planets and ends with the Universe as a whole.

To introduce the constituent objects of the Universe and the physics which allows us to estimate their distances, sizes, masses and natures. The module will show how our knowledge of the Universe beyond Earth relies upon the application and extrapolation of physics developed in the laboratory.


At the end of the module you should be able to:

  • List the main constituents of the Universe and give a basic description of them
  • Describe methods for measuring the distances of stars and galaxies and work out example computations.
  • Estimate the masses of stars and galaxies given information on size or angle & distance and speed.
  • Explain how the surface temperature of stars can be measured and how one can deduce physical conditions of their interiors.


Description of the main constituents of the Universe with typical sizes, masses and distances covering: the Solar System. Stars and star clusters Angles, distances & sizes: angular size and the small-angle approximation; trigonometric parallax; simple telescopes; distance methods based upon the inverse square law of brightness.

Masses: the Doppler effect and the measurement of speed from spectra; the use of speeds and sizes to derive masses in the Solar System, binary stars, star clusters and galaxies.

Physical properties of stars: stellar temperatures; spectra and elemental compositions. Physical conditions within stars

Galaxies: normal & active; the Milky Way; galaxy interactions; galaxy clusters.

The Universe: Hubble's discovery of the expansion of the Universe; implication of a finite age; the Cosmic Microwave Background; the composition of the Universe.

Commitment: 15 Lectures + 5 problems classes

Assessment: 1 hour examination

This module has a home page.

Recommended Texts: Marc Kutner, Astronomy: a Physical perspective , CUP

Leads from: A level Physics

Leads to: PX268 Stars