Cor Caroli is a double star in the constellation Canes Venatici. It’s best viewed in spring.
Also known as Alpha Canum Venaticorum, Cor Caroli is pretty double star and viewable in any size scope. The primary star, at a magnitude of 2.9, shines a white blue, while the dimmer companion, at a magnitude of 5.5, shines a warm yellow. This contrast of color makes for an attractive pair in the warming spring sky.
So what about the name Cor Caroli? Some say a physician by the name of Sir Charles Scarborough looked up on the evening of May 29, 1660, to observe a shiny bright star. Reflecting on the recent execution of Charles I and the new king Charles II, the good doctor named the star “Heart of Charles.” While this story seems like a fitting tribute, it is disputed today. See earthsky.org for more info on the story.
My Observations
| Date | April 22, 2021 |
| Time | 10:00 p.m. |
| Location | Seattle, WA |
| Magnification | 169x |
| Scope | Meade 8″ SCT |
| Eyepiece | 12mm |
| Seeing | Average |
| Transparency | Average |
I started my evening looking at the bright diamond-like stars of Castor. Moving from Castor, I’m now seeing Cor Caroli for the first time in a telescope. Castor may have brilliant white stars, but in comparison, I find Cor Caroli prettier based on a nice contrast of color. The larger star is sparkling white, much like Castor A. In contrast, the companion is a warm yellow with perhaps a tinge of green. This colorful double is a nice spring target.
Key Stats
| Constellation | Canes Venatici |
| Best Viewing | Spring |
| Visual Magnitude | +5.5 | +2.9 |
| Absolute Visual Magnitude | +2.64 |
| Separation | 19.3″ | 712 AU |
| Position Angle | 230° |
| Distance from Earth | 120 ly |
| Orbital Period | Unknown |
| Milky Way Location | Orion Spur |
| My Viewing Grade | B |
| Designations | SAO 63257, HIP 63125, Struve / STF 1692 |
Sources and Notes
Cor Corali banner photo was created with two images:
- Double star OGLE-LMC-CEP0227 in our neighboring galaxy, the Large Magellanic Cloud. This media was created by the European Southern Observatory (ESO).
- Photo of King Charles I by Jonathan Jansen, Essential Vermeer. This is a faithful photographic reproduction of a two-dimensional, public domain work of art.
Sketch by Wayne McGraw
The Garden Astronomer 