Canes Venatici, the Hunting Dogs, is a northern constellation located just below the handle of the Big Dipper. Although its two principal stars form only a simple line, the constellation contains some of the spring sky’s finest deep-sky objects, including the Whirlpool Galaxy (M51), the Whale Galaxy (NGC 4631), and the globular cluster Messier 3.
Covering approximately 465 square degrees, Canes Venatici is the 38th-largest of the 88 recognized constellations. It was introduced in the 17th century by Polish astronomer Johannes Hevelius.
Where and When to Find Canes Venatici
Canes Venatici is best seen from the Northern Hemisphere during spring, particularly from March through May. It lies south of Ursa Major and west of Boötes. Start with the Big Dipper’s curved handle. Just below it, look for Cor Caroli, a star of about magnitude 2.9. Farther west is the fainter star Chara. Together they mark the two hunting dogs in the traditional illustration. Although the constellation itself is relatively inconspicuous, its position near the Big Dipper makes it a useful starting point for finding several galaxies and star clusters.
History and Mythology
Canes Venatici means “hunting dogs” in Latin. Hevelius introduced it in his celestial atlas Firmamentum Sobiescianum, published in 1690, depicting two dogs named Asterion and Chara held by Boötes, the Herdsman. The region was not recognized as a separate constellation by Ptolemy, who listed its stars among those surrounding Ursa Major. Its later association with dogs arose through the development and interpretation of medieval star descriptions rather than a well-established ancient Greek myth.
Notable Stars
- Cor Caroli (Alpha Canum Venaticorum) is the brightest star in Canes Venatici, with a combined apparent magnitude of approximately 2.9. It is a double-star system roughly 110 light-years away, and its components can be separated with a small telescope. The brighter component, Alpha2 Canum Venaticorum, is a chemically peculiar star with a strong magnetic field. Its brightness changes slightly as it rotates, making it the prototype of the Alpha2 Canum Venaticorum class of variable stars. The name Cor Caroli means “Charles’s Heart.”
- Chara (Beta Canum Venaticorum) is a Sun-like main-sequence star about 27 light-years away, shining at magnitude 4.3. It is a useful comparison for astronomers studying stars broadly similar to our own Sun.
- La Superba (Y Canum Venaticorum) is a remarkable carbon star whose atmosphere contains compounds that absorb much of its blue light, giving it a deep red appearance. It is also a variable star, so its brightness changes over time. It is a rewarding target for observers interested in colorful stars.
- AM Canum Venaticorum (AM CVn) is the prototype of a rare class of extremely compact interacting binary systems. These systems contain a white dwarf accreting helium-rich material from a close companion, often another degenerate star. Their exceptionally short orbital periods make them important objects for studying stellar evolution and gravitational waves.
Notable Deep-Sky Objects
Whirlpool Galaxy (M51)
The Whirlpool Galaxy (Messier 51, NGC 5194) is one of the best-known examples of a grand-design spiral galaxy, with two prominent spiral arms wrapped around a bright central region. It lies approximately 30 million light-years away. M51 is interacting gravitationally with the smaller galaxy NGC 5195, visible beside it in photographs. Their interaction helps make the Whirlpool’s spiral structure especially striking.
Under dark skies, a moderate-sized telescope shows the galaxy as a faint glow with its companion nearby. Larger telescopes and favorable conditions are generally needed to make out the spiral arms. Despite its fame, M51 is not an easy binocular target from light-polluted cities.
Whale Galaxy (NGC 4631)
The Whale Galaxy (NGC 4631) is a large spiral galaxy seen nearly edge-on, approximately 25 million light-years away. Its elongated, uneven outline resembles a whale, giving the galaxy its popular nickname. Gravitational interactions with neighboring galaxies, including NGC 4627, have helped distort its shape. The galaxy also contains active star-forming regions and a halo of hot gas detectable in X-rays.
Through a telescope, the Whale Galaxy appears as a long, narrow streak of light. Larger instruments may reveal its uneven brightness and nearby companion.
Messier 3 (M3)
Messier 3 (NGC 5272) is one of the brightest globular clusters in the northern sky. Located about 34,000 light-years away, it contains hundreds of thousands of old stars bound together by gravity. At approximately magnitude 6.2, M3 is visible in binoculars as a small fuzzy patch. A moderate-sized telescope begins to resolve stars around its edges, while larger instruments reveal an impressive concentration of stars.
To locate M3, look between Cor Caroli and Arcturus in Boötes, where the cluster lies about one-third of the way from Arcturus toward Cor Caroli.
Other Galaxies
Canes Venatici is especially rich in galaxies. Other notable targets include the Sunflower Galaxy (M63), M94, and M106, all popular with amateur astronomers and astrophotographers. The constellation also contains the interacting Hockey Stick Galaxies (NGC 4656 and NGC 4657).
Observing Canes Venatici
Begin with Cor Caroli below the Big Dipper’s handle, then use the star as a landmark for exploring the surrounding sky. A small telescope can split Cor Caroli into its two components, while binoculars can reveal M3 as a faint patch.
For galaxies, choose a clear, moonless night away from city lights. M51 and the Whale Galaxy reward patience and low-to-moderate magnification, while M63, M94, and M106 offer additional challenges for observers with larger telescopes.