Page "Cygnus (constellation)" Paragraph 3
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Cygnus is also home to several variable stars.
Chi Cygni is a red giant and the second-brightest Mira variable star at its maximum.
Its maximum magnitude is 3. 3 and its minimum magnitude is 14 ; it has a diameter of 300 solar diameters.
Chi Cygni has a period of 400 days and is 350 light-years from Earth.
P Cygni is a large, unstable blue supergiant that is evolving into a red supergiant.
In 1600, it brightened suddenly to 3rd magnitude, though its normal magnitude is approximately 5.
It began to brighten gradually in the 1700s and has continued to brighten to the present day ; this is part of the process of stellar evolution.
W Cygni is a semi-regular variable red giant star, 618 light-years from Earth.
It has a maximum magnitude of 5 and a minimum magnitude 8 ; its period of 130 days.
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1.944 seconds.