Star for September

Albireo, the middle star of the Summer Triangle

This month look for the star Albireo in the constellation of Cygnus the Swan. Astronomers call

Albireo is a fun star if you have at least a small telescope. To the naked eye, the star appears as a non-descript white point of light. However, in a telescope, even at low power, it splits into two stars, each star distinctly tinted. I see them as golden-yellow and cyan. Others that I’ve asked see more green in the bluish star than I do.    

Stars can have subtle colors, but most are too faint for us to make out their color. It usually takes the light gathering ability of a telescope to bring out a star’s color (if it has any). In the case of Albireo, the close proximity between the two stars lets our eyes and brain exaggerate their subtle differences in hue. If you have trouble seeing color differences, try setting your telescope slightly out of focus.

The light you see from Albireo tonight left 380 years ago, or in the year 1635. At a distance of 380 light years, the stars must be immensely far apart to have the separation we see on Earth. That separation makes it difficult for the stars to remain in orbit around each other; therefore, it’s possible that Albireo represents a chance alignment of stars and not a true binary. If they are orbiting each other, then their orbital period is on the order of 75,000 years.

Albireo Beta Cygni, but it’s not actually the second brightest star of the constellation as its name might lead you to believe. Albireo is a reasonably bright star however, and it’s located at the southern end of the constellation or near the center of the Summer Triangle (the triangle consists of the stars Deneb, Vega, and Altair). In Cygnus, Albireo represents the beak of the swan.

 Look for Cygnus and Albireo overhead during September. The swan is flying to the south, perhaps in preparation for the oncoming winter.