Beta Cephei, known by its traditional name of Alfirk, makes its home in the fall constellation of Cepheus. The beautiful blue star is a giant that burns at a temperature of 26,000 Kelvin (approximately 46,000 degrees Fahrenheit). The star has 12 times more mass than our Sun and has a luminosity equal to 14,600 Suns. No wonder the naked eye can see this star from suburban skies, even though it is 595 light-years away!
Historically speaking, a Timurid sultan by the name of Ulugh Beg cataloged the star under the name of Alfirk. Alfirk is derived from the Arabic word al-firqah “the flock” (of sheep).
My Observations
| Date | September 2, 2021 |
| Time | 10:00 p.m. |
| Location | Seattle, WA |
| Magnification | 169x |
| Scope | Meade 8″ SCT |
| Eyepiece | 12mm |
| Seeing | Average |
| Transparency | Average, light haze |
Though I’m observing during the waning days of summer, the winter holidays come to mind when I view Alfirk. The colors on this double remind me of Christmas lights, with the light blue of Alfirk in contrast to the dimmer and smaller companion, which appears red, although I believe most charts show it as white. Also, I will have to confirm my observation, but I’m only able to see two stars, not three.
Backyard Photo
Key Stats
| Constellation | Cepheus |
| Best Viewing | Autumn |
| Visual Magnitude | +3.2 | +8.6 |
| Absolute Visual Magnitude | -3.38 |
| Separation | 13.5″ | 2840 AU |
| Position Angle | 251° |
| Distance from Earth | 690 ly |
| Orbital Period | .190 days |
| Milky Way Location | Orion Spur |
| My Viewing Grade | B |
| Designations | SAO 10057, Alphirk, 8 Cep, Struve / STF 2806 |
Sources and Notes
Banner photo shared from Wikisky. Reference here.
Sketch by Wayne McGraw
The Garden Astronomer 