Celestia Forums

I found a reference on SIMBAD to 61 Cyg A being a "variable of BY Dra type". Searching around the net I find that BY Draconis variability is caused by the rotation of the star. How significant is this variability and would it be likely to affect the habitability of a planet of 61 Cyg A?

The variability of BY Dra variables is a little ... variable. Some stars can change by half a magnitude or more as large starspots rotate in and out of view. 61 Cyg A seems to be a lesser case, though: this list of BY Dra variables shows it changing visual magnitude by only 0.08, equivalent to about an 8% change in brightness, taking place within a stellar rotation period.
The bolometric change is probably less than that, given that the visual output is much more sensitive to temperature change than the total energy output, in cool stars.

Grant