The Variable Star Section was formed in June 1998 to educate and assist members to observe stars that change in brightness. Members are encouraged to submit their observations to international databases (AAVSO, RASNZ etc) where the data is used by professional astronomers to determine how stars behave and evolve over time. Variable star observing is one of the few fields where amateur astronomers can make a real contribution to the science of astronomy.

The Variable Star Section of the Astronomical Association of Queensland comprises a group of people who have a research interest in stars that vary in brightness over time. We are also members of other organizations that promote the study of variable stars, including the American Association of Variable Star Observers (AAVSO) (www.aavso.org) and Variable Stars South (www.variablestarssouth.org). Members of the Variable Stars Section have published papers base on their results in refereed journals, an example of the fact that amateur astronomers can make significant contributions to this field of astronomy.

There are several types of variable stars, and their detailed classification is quite complex. Stars vary in brightness due to the effects of one or more physical processes. Some of these processes are:

  • Pulsation over regular or irregular cycles, with expansion and contraction of the outer layers of the stars, resulting in changes in surface temperature and therefore changes in brightness and colour. Examples are long period variables such as those of Mira type, and short period pulsating stars of the delta Scuti type.
  • Rotation of stars with non-uniform surface brightness and/or ellipsoidal shapes. The non-uniform brightness in the surface of the star may be due, for example, to starspots (equivalent to sunspots on the Sun, but much larger).
  • Cataclysmic events in which stars show sudden, dramatic increases in their brightness caused by thermonuclear processes in their surface layers (novae) or deep in the interior (supernovae). These are examples of cataclysmic variables. Every year, several novae in our galaxy and supernovae in other galaxies are discovered by amateur astronomers.
  • Eclipse of one star by a nearby companion. These are close (in the sense of distance between the stars) binary eclipsing stars, with the planes of the orbits parallel (or nearly parallel) to the line of sight from Earth. When one star passes between earth and the other star, the apparent brightness of the system decreases. Detailed studies of such events allow astrophysical properties of the eclipsing systems (such as masses of the stars) to be determined from amateur observations.

Further reading

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Most recent papers by members

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