Canes Venatici
“The Hunting Dogs” · Northern · best around May evenings
Real star positions and magnitudes (HYG database via D3-Celestial, BSD-3). Lines are the conventional stick figure; north is up.
The story
The herdsman's two dogs, leaping beneath the Big Dipper's handle. Small but disproportionately rich: it holds the Whirlpool Galaxy — the first spiral structure ever seen (1845) — and the great globular M3.
How to find it
Directly under the Dipper's handle in spring.
✦ What lives inside it
- M3 globular
The deep dive
Researched for the Atlas from Wikipedia — Canes Venatici (8,127 characters read) · updated Sep 20, 2026
01 A constellation born from a mistranslation
Canes Venatici owes its very existence to a chain of translation errors stretching across three languages and several centuries. The stars that now form the constellation were originally listed by Ptolemy in his Almagest as unfigured — that is, unnamed and unassigned to any figure — sitting loosely beneath Ursa Major. Some of Boötes's stars were traditionally said to represent his club, using the Greek word kollórobon. When the Almagest was translated from Greek into Arabic, the translator Hunayn ibn Ishaq did not recognize the word and rendered it as al-ʿaṣā ḏāt al-kullāb, meaning 'the staff having a hook.' When Gerard of Cremona later translated that Arabic text into Latin, he mistook kullāb, meaning 'hook,' for kilāb, meaning 'dogs' — two words that look identical in Arabic script when diacritical marks are omitted. Gerard therefore wrote Hastile habens canes, or 'spearshaft-having dogs.' By 1533, the German astronomer Peter Apian was already depicting Boötes accompanied by two dogs, cementing the error in the visual tradition of star atlases.
02 Hevelius and the dogs that made history
Once the spurious dogs had drifted through the astronomical literature for well over a century, Johannes Hevelius formalized them as an independent constellation in 1687, giving them the name Canes Venatici — Latin for 'the hunting dogs.' In his star atlas he assigned the individual names Asterion to the northern dog and Chara to the southern dog. The Czech astronomer Antonín Bečvář later mapped those names onto specific stars, assigning Asterion to Beta Canum Venaticorum and Chara to Alpha Canum Venaticorum. Chara comes from the Greek word for joy. When the International Astronomical Union rationalized the sky in 1930 and dropped several medieval and Renaissance constellation inventions, Canes Venatici survived, becoming one of the 88 officially designated constellations. Belgian astronomer Eugène Delporte set the official boundaries that same year as a 14-sided polygon, with right ascension running from 12h 06.2m to 14h 07.3m and declination from +27.84° to +52.36°. The constellation covers 465 square degrees, ranking it 38th in size among the 88.
03 Cor Caroli: a royal star with a magnetic secret Deeper
Alpha Canum Venaticorum bears the name Cor Caroli, Latin for 'heart of Charles,' given by the English physician Sir Charles Scarborough in memory of the executed King Charles I of Britain. The astronomer William Henry Smyth wrote in 1844 that the star appeared notably brighter when Charles II returned to England at the Restoration, though Smyth offered no source for this claim and it is now widely regarded as apocryphal. What is not apocryphal is the star's physical character. Cor Caroli is a wide visual double star: the primary shines at magnitude 2.9 and lies 110 light-years from Earth, while a secondary companion glows at magnitude 5.6. The primary star hosts an unusually strong variable magnetic field — a rare and scientifically interesting property that sets it apart from the great majority of stars of its type. Beta Canum Venaticorum, Chara, is a yellow main-sequence star of magnitude 4.25 at just 27 light-years from Earth. Because of its closeness and similarity to the Sun, it has been placed on lists of astrobiologically interesting stars, though no exoplanets have yet been found orbiting it.
04 La Superba: one of the reddest stars you can see
Y Canum Venaticorum earned its dramatic nickname La Superba because of its startling deep-red color, which can be glimpsed without a telescope on a clear night from a dark location. It belongs to the rare class of carbon stars — stars whose atmospheres are so rich in carbon molecules that they absorb blue and green light heavily, leaving the red wavelengths to dominate. Its spectral type is catalogued as C54J(N3). La Superba is also a semiregular variable star, pulsing between magnitudes 5.0 and 6.5 on a cycle of roughly 158 days — so its brightness can change noticeably over the course of about five months. The variation is semiregular rather than strictly periodic, meaning careful long-term observation is needed to track its rhythms. Few targets in the northern sky demonstrate so vividly, to a naked eye or binoculars, how different a star's color can be from the familiar white or pale yellow of most bright stars.
05 Two prototype variables hiding in the dogs Deeper
Beyond La Superba, Canes Venatici harbors two stars that hold a special scientific status: they are the prototypes of their entire class, meaning that when astronomers discovered unusual behavior in other stars elsewhere in the sky, they defined the category by reference back to these two. AM Canum Venaticorum is a very blue star of magnitude 14, 143 parsecs from the Sun, and is the prototype of a class of cataclysmic variable stars in which the donor companion is not an ordinary main-sequence star but another white dwarf. This makes the system doubly compact and produces behavior quite different from classical novae. RS Canum Venaticorum is the prototype of a class of binary stars characterized by chromospheric activity and optical variability — essentially, pairs of stars with unusually energetic outer atmospheres that cause measurable brightness changes. Meanwhile, R Canum Venaticorum is a Mira variable whose brightness ranges all the way from magnitude 6.5 down to 12.9, a factor of well over a hundred in actual light output, over a period of approximately 329 days.
06 The Whirlpool: where spiral arms were discovered
M51, the Whirlpool Galaxy, holds a unique place in the history of astronomy: it was the first galaxy in which spiral structure was ever recognized. Lord Rosse made that observation in 1845 using the enormous reflecting telescope he had built at Birr Castle in Ireland. M51 lies 37 million light-years from Earth and happens to be oriented nearly face-on toward us, which is exactly why its sweeping spiral arms are so beautifully displayed. Those arms are studded with star-forming regions and nebulae that color them pink and blue, standing out against the older, yellower stellar population in the galaxy's core. M51 is not alone: it has a smaller companion galaxy, NGC 5195, which appears yellow because it contains very few star-forming regions. NGC 5195 is currently passing behind M51, and astronomers think this gravitational interaction may be responsible for triggering M51's unusually vigorous star formation. Together the pair is widely considered one of the most visually stunning galaxy systems in the sky.
07 M94's ultraviolet ring and its invisible bar Deeper
M94, also catalogued as NGC 4736, looks at first glance like a compact, bright-cored face-on spiral galaxy at roughly magnitude 8.0, about 15 million light-years from Earth. Its tight spiral arms and luminous nucleus make it a satisfying telescopic target. But the more surprising feature is invisible to ordinary optical telescopes: the outskirts of M94 blaze in ultraviolet light because of a ring of newly forming stars surrounding the core, a ring measuring 7,000 light-years in diameter. What triggered this ring of star formation? Astronomers are genuinely uncertain. One hypothesis is that shock waves from a bar at the galaxy's center — a bar that remains undetected so far in visible light — compressed the surrounding gas and set off the burst of new star birth. M94 therefore presents a puzzle: a feature that can be seen clearly in one wavelength but whose proposed driver remains invisible in another, which is exactly the kind of open question that keeps extragalactic astronomers occupied.
08 M3: the globular you can see without a telescope
Not every landmark in Canes Venatici is a galaxy. M3, formally catalogued as NGC 5272, is one of the finest globular clusters in the northern sky — a gravitationally bound swarm of ancient stars sitting 32,000 light-years from Earth. It spans 18 arcminutes in apparent diameter, roughly six-tenths the width of the full Moon as seen from Earth, and shines at magnitude 6.3. That is bright enough to spot with a good pair of binoculars from a suburban sky, and under particularly dark conditions it can even be glimpsed with the unaided eye. Globular clusters like M3 are among the oldest structures in the galaxy, containing stars that formed billions of years before the Sun existed. In a small telescope the cluster resolves into thousands of individual points of light packed most densely toward the center, thinning out gradually toward the edges — a view that rewards even a modest instrument.
09 TON 618: a black hole of almost unimaginable mass Deeper
Near the border of Canes Venatici with the neighboring constellation Coma Berenices lies one of the most extreme objects known to science: TON 618, a hyperluminous quasar and blazar. At its heart is a black hole with a mass 66 billion times that of the Sun. To put that number in some kind of context, the black hole at the center of the Milky Way masses roughly 4 million solar masses — TON 618's black hole is more than ten thousand times heavier than that. It is one of the most massive black holes ever measured. Quasars like TON 618 are the intensely luminous cores of distant active galaxies, powered by matter falling into a supermassive black hole and releasing enormous amounts of energy. TON 618's classification as both a quasar and a blazar indicates that its relativistic jet is pointed roughly in our direction, adding to its apparent brilliance. A Lyman-alpha blob is also associated with this object, one of the largest and most energetic types of nebulae known.
10 A colossal void lurking in the background Deeper
Behind the visible stars and galaxies of Canes Venatici lies something defined by its very emptiness: the Giant Void, an immense region of the universe containing far fewer galaxies than would normally be expected. Discovered in 1988 during a deep-sky survey, it is regarded as the second largest void ever found — slightly larger than the Eridanus Supervoid, though smaller than the proposed KBC Void — and its volume is approximately 1,200 times that of a typical void. Its center is roughly 1.5 billion light-years away from Earth. Voids are not perfectly empty; they contain some galaxies and dark matter, but at a far lower density than the walls and filaments of the cosmic web that surround them. The Giant Void's scale makes it cosmologically significant: structures of that size probe how matter clustered in the early universe and help test models of large-scale cosmic structure. Its existence in the direction of Canes Venatici is a reminder that the constellation's boundaries contain not just nearby stars but some of the grandest architecture in the observable universe.
11 The Sunflower and the edge-on NGC 4631
M63, nicknamed the Sunflower Galaxy after the way it appears in large amateur telescopes, is a spiral galaxy with an integrated magnitude of 9.0. Its mottled, textured arms give it a distinctly organic appearance that earns the name even in photographs taken with modest equipment. M106, also catalogued as NGC 4258, is another notable spiral in the constellation and a frequent target for deep-sky observers. NGC 4631 provides a completely different viewing geometry: it is a barred spiral galaxy seen nearly perfectly edge-on from Earth, which makes it one of the largest and brightest edge-on galaxies in the sky. Edge-on views reveal the flat disk structure of spiral galaxies in a way that face-on orientations cannot, often showing a dark dust lane running along the galaxy's equatorial plane. Canes Venatici therefore offers observers the rare opportunity to compare face-on spirals, like M51 and M94, with an edge-on system like NGC 4631, all within a single modest-sized constellation spanning 465 square degrees.