Definition of Canes Venatici Constellation
|Latin Name||Canes Venatici|
|Adjoining Constellations||Bootes, Ursa Major, Leo, Coma Berenices|
|Fully visible region||90°N~37°S|
|Other information||originally part of Ursa Major|
Canes Venatici is a small constellation in the northern sky. It was created by Polish astronomer Johannes Hevelius to represent Chara and Asterion (the two dogs led by Bootes) in the 17th century. It is one of the three constellations representing the dog, along with Canis Major and Canis Minor.
The range occupied by CVn: right ascension 12h4min ~ 14h5min; declination +28°~ +53°; an area of 467 square degrees. There are 42 stars brighter than magnitude 6 in CVn, but most of them are dark.
The Way to Find Canes Venatici
- α CVn can be found by taking a straight line from α and γ in Ursa Major and extending about twice in the direction of Arctura.
- CVn forms an equilateral triangle with β Leo and Arcturus in Bootes, which can be also used to find it.
Stars in Canes Venatici
With the exception of α and β, all of the stars in CVn are dark, so this constellation looks deserted, not to see the appearance of a hound.
On moonless nights, a very faint star can be found halfway between α CVn and Arcturus, sometimes even with the help of a small telescope. However, if you use a large telescope, you will find it is not just a single star, but a cluster of more than 200,000 stars.
This large, spherical star cluster in CVn is 40 light-years across and is known astronomically as “a globular cluster”. To the north of Canes Venatici lies a spiral galaxy, about 14 million light-years away from us, which is the CVn galaxy.
α CVn is a binary system with the magnitude of 2.9 and 5.6 respectively. Both of them are white, but some observers claim to see light colors. Through spectroscopic studies, it could be that the brighter one has an unusual composition.
The M3 globular cluster is about half a full moon in size. To observe each star in the cluster, you must use a telescope with a diameter of more than 10 cm.
Deep Sky Objects
CVn contains five Messier objects. One is the spiral galaxy, known as M51, which contains NGC 5194 and NGC 5195, an irregular galaxy facing Earth that was observed by William Parsons in 1845. It is the first galaxy thought to have a spiral structure.
Canes Venatici also includes the Sunflower galaxy (M63 or NGC 5055), spiral galaxy M94, and spiral galaxy M106.
The famous spiral galaxy M51 was one of the first objects discovered by Charles Messier. On October 13, 1773, while observing a comet, Messier discovered it and described it as a “very dark nebula, without of stars” and difficult to observe. Its companion galaxy, NGC 5195, was discovered by his friend Pierre Mechain in 1781 and was also mentioned in the 1784 edition of Messier’s catalog: “This is a double nebula, with each part having a bright core. They are 4’35” away from each other. Their ‘atmospheres’ are connected, with one darker than the other.” William Herschel also assigned NGC 5195 his own name: H I.186.
There was occasional confusion about what M51 really meant: whether it referred to this pair of galaxies (like the two “nebulae” Messier mentioned) or just the larger galaxy, NGC 5194. For this pair of galaxies, NGC 5194 would be known as M51A, and NGC 5195 as M51B.
The distance to M51 (and to the entire galaxy cluster) is still very unclear. The 37 million light years that we used were based on photometric measurements, the same numbers that Kenneth Glyn Jones gave. Some authors have given much smaller numbers (less than 20 million light-years), but the most recent (2001) STScI published a figure of 31 million light-years. In the spring of 1845, Sir Rosse discovered the spiral arm structure in M51. This is the first time such structure to be discovered. Sir Rosse also made a very careful and accurate sketch. As a result, M51 is sometimes referred to as the Rosse galaxy or Sir Rosse’s “question mark” — that’s how he described M51.
As our understanding at present, the prominent spiral arms are the result of M51’s recent encounter with its nearest neighbor, NGC 5195 (the darker one in Messier’s description). With such interactions, the gas in some regions of the galaxy is disturbed and compressed, resulting in the formation of new young stars. This is common in galactic encounters, where spiral arms are more likely to occur in heavier galaxies. Halton Arp included M51 as object No. 85 in his list of irregular galaxies, describing it as a “whirlpool galaxy with a large companion galaxy of high surface brightness.”
M51 is an easy and beautiful target for enthusiasts if the sky is dark enough, but it is sensitive to light pollution and easily gets lost in the sky light background. In excellent conditions, the spiral arms can be glimpsed even with a telescope of more than four inches. Low magnification is best for viewing this pair of galaxies. The Hubble space telescope focuses on the central region of M51. Its dense core is now classified as Seyfert type 2.5.
Recent HST research (published in 2001) focused on inner spiral arms and dust clouds, where massive bright stars form. The European Space Agency’s ISO (Infrared Space Observatory) satellite has studied spiral galaxies in infrared wavelengths.
This misty cloud, is close to Ursa Major and surrounded by many stars in CVn. It also has a number M106. Modern telescope observations suggest it is a cosmic island (that is, a galaxy outside the Milky Way), about 21 million light-years away from us. M106’s beautiful spiral arms are highlighted by its numerous young blue star clusters and red stellar nurseries. The bright galactic core in this beautiful image is visible in all wavelengths, from radio waves to X-rays, making it the nearest active galaxy to us. Such galaxies are thought to have very bright cores, caused by the intense radiation emitted by matter falling into the massive black hole at its center.
What’s at the core of M106?
M106 is a spiral disk galaxy of stars and gas. The main features of its appearance are two bright swirling arms and a dark dust belt near the core. In the image above, the new star near the tip of its spiral arm makes the arm stand out. M106 emits intense radio and X-ray radiation from its core, and astronomers recently discovered that it has two jets almost as long as the galaxy. M106 has a bright core, and astronomers believe that M106 has a supermassive black hole at its center. As matter falls into the black hole, it rubs against each other so violently that the gas masses near its core glow brightly. M106 is also often referred to as NGC4258.
Mythology of Canes Venatici
There was a goddess called Callisto, who was gentle and beautiful. The god Zeus loved her very much. After, she gave birth to a son named Arcas. Hera knew it and turned Callisto into a big bear. Then, Arcas grew up to be a fairly good hunter, but he did not know his mother’s suffering.
One day Hera asked the god of destiny to let Arcas and his mother bear meet in the forest. When the mother saw her son, whom she had missed for so many years, she was so excited that she forgot that she had become a big bear. She could not help running to Arcas, who thought that the bear was going to hurt him and immediately raised an arrow to shoot it.
On the verge of great matricide, Zeus broke through the knot of guilt and cowardice and turned Arcas into a bear too, then he placed them in the sky as the Ursa Major and Ursa Minor, so that they could be together forever. But Hera still not gave up, she sent a shepherd, leading two hounds, after the big bear and small bear. At all times, the hounds followed closely behind the two bears, faithfully serving the mission given by Hera.
Another myth is that the Canes Venatici, which means the guard of the bears, was sent by Zeus to protect Callisto and Arcas.