Alpha2 Canum Venaticorum — Double Star in Canes Venatici
COR CAROLI
About Alpha2 CVn
Description
Cor Caroli is a chemically peculiar star of spectral type A0pSiEuHg at magnitude 2.90, the brightest star in Canes Venatici (the Hunting Dogs). Located about 110 light-years from Earth, it is the prototype of the Alpha2 Canum Venaticorum class of magnetic variable stars, with starspots of concentrated silicon, europium, and mercury. It is a wide double with a fainter companion visible in small telescopes.
Observing Tips
Cor Caroli lies below the handle of the Big Dipper, about 7 degrees south of Alkaid. A small telescope reveals the companion (magnitude 5.5) about 19 arcseconds away. It is the starting point for finding the Whirlpool Galaxy (M51) and other Canes Venatici deep-sky objects. Best observed March through July.
History
The name Cor Caroli means 'the Heart of Charles,' named by Edmund Halley in honor of King Charles I of England (some sources say Charles II). It is one of the few bright stars named after a modern historical figure rather than derived from Arabic or classical sources.
Fun Facts
Cor Caroli defines an entire class of chemically peculiar variable stars. Its strong magnetic field concentrates rare elements into spots on its surface, causing small brightness variations as it rotates — a stellar version of sunspots, but driven by magnetic chemistry.
Observe
1Physical Properties
2Position & Identifiers
3How easy to split?
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | Easy | Easy | Easy |
| 150 mm Newton 150mm Newt. | Easy | Easy | Easy |
| Celestron C8 (203 mm SCT) C8 203mm | Easy | Easy | Easy |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
4Visibility
Set a location in User Settings to see visibility data.
5Light Curve
6Multiple Star System
Separation over time
Slow change over generations — observable in lifetime comparisons.
Measured from the WDS observational archive. No orbital solution has been derived — most likely the period is too long to fit an orbit to the available measurement arc.
Eyepiece View
A: 2.9 · B: 5.5 · Sep: 19.2″ · PA: 229° · N up, E left
Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 2.3″
Explore
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Size Comparison
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Compare Stars
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Spectral Classification
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Hertzsprung-Russell Diagram
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Stellar Lifecycle
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Blackbody Spectrum
14
Stellar Absorption Spectrum
Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.
15
Stellar Fusion
Discover
16Stellar Notes
17
Light Travel Time Machine
18
Relativistic Travel
Survey Image
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Nearby in the Sky
Other targets within a few degrees — pan your scope a little and keep exploring.
Visibility scores assume a 150 mm Newton at Bortle 4.
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