Amateurs help solve SS Cyg mystery

Amateur observations of the dwarf nova SS Cygni have tipped off professionals to point their radio telescopes to this cataclysmic variable star during outbursts. This has led to a parallax-based refinement of the distance to SS Cyg of around 372 light years instead of 450, and the realisation that it is not as intrinsically bright as was previously thought.

The earlier less accurate HST-based parallax measurement suggested that, in theory, its intrinsic brightness was too high for periodic outbursts to occur and that rather, it ought to be in a stuck-in-outburst state. The revised smaller distance value means that the brightness observed agrees with the outburst behaviour theoretical models for this type of variable star predict.

Here’s the AAVSO summary article regarding the discovery and a light curve of SS Cygni from the AAVSO International Database showing such outbursts (Visual and photometric V band observations):


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