variable star: Eruptive Variables

The eruptive variables are highly unstable stars that suddenly and unpredictably increase in brightness. T Tauri stars, also known as nebular variables because they are young objects still embedded in nebulosity, are the least violent of these explosive stars. Novas and supernovas are much more dramatic. Novas are small, very hot stars that suddenly increase thousands of times in luminosity. Their decline in luminosity is much slower, taking months or even years. Most novas probably repeat their outbursts, the dwarf novas every few months, the recurring novas every few years or decades, and the standard novas over thousands of years. Supernovas, upon exploding, increase millions of times in brightness and are totally disrupted. More than 30 supernovas events are observed annually in distant galaxies. Three supernovas have been seen in our own galaxy, in 1054, 1572, and 1604; in 1987 a supernova erupted in a neighboring galaxy, the Large Magellanic Cloud.

Sections in this article:

• Introduction
• Extrinsic Variable Stars
• Eruptive Variables
• Pulsating Variables
• Bibliography

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