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The Mira type variable Chi Cygni isn't due to reach its peak brightness until late October ... but it is already visible in binoculars. Recent observations place it at around magnitude 8.6.
Chi Cygni is a red giant star whose brightness variations are due to pulsations in its tenuous outer layers. These cause the surface temperature to rise and fall and this in turn causes its brightness to rise and fall. Additional "irregularities" relate to the formation and splitting of simple molecules in the star's cooler surface layers.
The peak brightness of chi Cygni differs from one cycle to the next and cannot be predicted in advance. The average peak is around magnitude 5.1, but the spring 2013 peak reached around magnitude 3.8, whereas that of early summer 2014 only managed around magnitude 6.4.
Chi Cygni lies in the "neck" of the constellation of Cygnus the Swan, not far from the star Eta Cygni (mag 4.0), as can be seen in the finder chart shown below, which is approx 3 degrees by 4 degrees.
You can follow the brightening of Chi Cygni over the coming months by comparing its brightness with that of the comparison stars labelled on the chart. Currently, it is fainter than comparison K but brighter than comparison M.
More information about Chi Cygni can be found in this guide
Added by: Tracie Heywood