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Astronomy From West Virginia

OBSERVING VARIABLE STAR P CYGNI PHOTOMETRICALLY - JULY 20, 2009

BRIDGEPORT, WV ( S-M) - Here at our observatory, we have been making photometric observations of the star P Cygni, in the constellation Cygnus. Our observations are to support the work of Ernst Pollmann, of the Spectroscopy Group of the Swiss Astronomical Society.

We started monitoring P Cygni several months ago, just after the star emerged into the morning sky from behind the Sun. The star is a luminous blue variable, and its variations are small enough that it is unlikely they could be detected by the eye. Our observations since April have shown variations in the star between magnitude 4.68 and 4.90, as measured through a standard Johnson V filter. It is the hope of Mr. Pollmann that corellating these photometric measures with spectral changes observed by his group will shed new light on the internal workings of the star.

Such studies have more than just academic value. Over time, our Sun will show variations which will affect our lives here on Earth. The study of variable stars like P Cygni will give us new insight into the processes which cause stellar variability, and may allow humanity to prepare for our own star's future.

We are making our measurements of P Cygni with an Optec SSP-3 solid state photometer. The measurements are made differentially, that is, by determining the difference in brightness between P Cygni and a comparison star. We use the star SAO 69101 as our comparison star. This star is magitude 4.936, and we generally find a difference between it and P Cygni of -.17 to -.2 magnitude. - GW

This chart shows P Cygni oscillating between about magnitude 4.7 and 5.0 over the past 200 days.  Courtesy Ernst Pollmann