Canis Minor is a small constellation in the northern celestial hemisphere. Its name is Latin for ‘lesser dog,’ in contrast to Canis Major, the ‘greater dog;’ both figures are commonly represented as following the constellation of Orion the hunter. Canis Minor is the 71st largest constellation in the sky, occupying an area of 183 square degrees. It lies in the second quadrant of the northern hemisphere (NQ2) and can be seen at latitudes between +90° and -75°. The neighboring constellations are Cancer, Gemini, Hydra, and Monoceros.
[http://www.constellation-guide.com/constellation-list/canis-minor-constellation/]
Lying directly south of Gemini’s bright stars Castor and Pollux, it does not border Canis Major; Monoceros is in between the two. It appears prominently in the southern sky during the Northern Hemisphere’s winter. Most visible in the evening sky from January to March, Canis Minor is most prominent at 10 PM during mid-February. It is then seen earlier in the evening until July, when it is only visible after sunset before setting itself, and rising in the morning sky before dawn.
Canis Minor, as depicted by Johann Bode in his 1801 work Uranographia
Though strongly associated with the Classical Greek uranographic tradition, Canis Minor originates from ancient Mesopotamia. Procyon and Gomeisa were called MASH.TAB.BA or ‘twins’ in the Three Stars Each tablets, dating to around 1100 BCE. In the later MUL.APIN, this name was also applied to the pairs of Pi3 and Pi4 Orionis and Zeta and Xi Orionis. The meaning of MASH.TAB.BA evolved as well, becoming the twin deities Lulal and Latarak, who are on the opposite side of the sky from Papsukal, the True Shepherd of Heaven in Babylonian mythology. Canis Minor was also given the name DAR.LUGAL, which translates to ‘the star which stands behind it,’ in the MUL.APIN; the constellation represents a rooster. This name may have also referred to the constellation Lepus. DAR.LUGAL was also denoted DAR.MUŠEN and DAR.LUGAL.MUŠEN in Babylonia. Canis Minor was then called tarlugallu in Akkadian astronomy.
Canis Minor was one of the original 48 constellations formulated by Ptolemy in his second-century Almagest, in which it was defined as a specific pattern (asterism) of stars; Ptolemy identified only two stars and hence no depiction was possible. The Ancient Greeks called the constellation ‘προκύων’ (Procyon), ‘coming before the dog,’ transliterated into Latin as Antecanis, Praecanis, or variations thereof, by Cicero and others. In Greek mythology, Canis Minor was sometimes connected with the Teumessian Fox, a beast turned into stone with its hunter, Laelaps, by Zeus, who placed them in heaven as Canis Major (Laelaps) and Canis Minor (Teumessian Fox). Eratosthenes accompanied the Little Dog with Orion, while Hyginus linked the constellation with Maera, a dog owned by Icarius of Athens. On discovering the latter’s death, the dog and Icarius’ daughter Erigone took their lives and all three were placed in the sky- Erigone as Virgo and Icarius as Boötes. As a reward for his faithfulness, the dog was placed along the ‘banks’ of the Milky Way, which the ancients believed to be a heavenly river, where he would never suffer from thirst.
The medieval Arabic astronomers maintained the depiction of Canis Minor (‘al-Kalb al-Asghar’ in Arabic) as a dog; in his Book of the Fixed Stars, Abd al-Rahman al-Sufi included a diagram of the constellation with a canine figure superimposed. There was one slight difference between the Ptolemaic vision of Canis Minor and the Arabic; al-Sufi claims Mirzam, now assigned to Orion, as part of both Canis Minor- the collar of the dog- and its modern home. The Arabic names for both Procyon and Gomeisa alluded to their proximity and resemblance to Sirius, though they were not direct translations of the Greek; Procyon was called ‘ash-Shira ash-Shamiya,’ ‘the Syrian Sirius’ and Gomeisa was called ‘ash-Shira al-Ghamisa,’ ‘the Sirius with bleary eyes.’ Among the Merazig of Tunisia, shepherds note six constellations that mark the passage of the dry, hot season. One of them, called Merzem, includes the stars of Canis Minor and Canis Major and is the herald of two weeks of hot weather.
The ancient Egyptians thought of this constellation as Anubis, the jackal god.
In Chinese astronomy, the stars corresponding to Canis Minor lie in the Vermilion Bird of the South (Nán Fāng Zhū Què). Procyon, Gomeisa and Eta Canis Minoris form an asterism known as Nánhé, the Southern River. With its counterpart, the Northern River Beihe (Castor and Pollux), Nánhé was also associated with a gate or sentry. Along with Zeta and 8 Cancri, 6 Canis Minoris and 11 Canis Minoris formed the asterism Shuiwei, which literally means ‘water level.’ Combined with additional stars in Gemini, Shuiwei represented an official who managed floodwaters or a marker of the water level.
Neighboring Korea recognized four stars in Canis Minor as part of a different constellation, ‘the position of the water.’ This constellation was located in the Red Bird, the southern portion of the sky.
Polynesian peoples often did not recognize Canis Minor as a constellation, but they saw Procyon as significant and often named it; in the Tuamotu Archipelago it was known as Hiro, meaning ‘twist as a thread of coconut fiber,’ and Kopu-nui-o-Hiro (‘great paunch of Hiro’), which was either a name for the modern figure of Canis Minor or an alternative name for Procyon. Other names included Vena (after a goddess), on Mangaia and Puanga-hori (false Puanga, the name for Rigel), in New Zealand. In the Society Islands, Procyon was called ‘Ana-tahua-vahine-o-toa-te-manava,’ literally ‘Aster the priestess of brave heart,’ figuratively the ‘pillar for elocution.’ The Wardaman people of the Northern Territory in Australia gave Procyon and Gomeisa the names Magum and Gurumana, describing them as humans who were transformed into gum trees in the dreamtime. Although their skin had turned to bark, they were able to speak with a human voice by rustling their leaves.
The Aztec calendar was related to their cosmology. The stars of Canis Minor were incorporated along with some stars of Orion and Gemini into an asterism associated with the day called ‘Water.’
[http://barkpost.com/dogs-in-the-sky-canine-constellations/]
[http://astropixels.com/constellations/charts/CMi.html]
Canis Minor
[http://astropixels.com/constellations/photos/CMi-01.html]
Procyon (Alpha Canis Minoris) is the brightest star in the constellation Canis Minor. To the naked eye, it appears to be a single star, the eighth brightest in the night sky with a visual apparent magnitude of 0.34. Its name comes from the Ancient Greek ‘Προκύων’ (Prokyon), meaning ‘before the dog,’ since it precedes the ‘Dog Star’ Sirius as it travels across the sky due to Earth’s rotation.
The reason for its brightness is not its intrinsic luminosity but its relative closeness to the Sun. As determined by the European Space Agency Hipparcos astrometry satellite, it lies at a distance of just 11.46 light-years (3.51 parsecs), and is therefore one of our nearest stellar neighbours. Its closest neighboring star is Luyten’s Star, about 1.12 ly (0.34 pc) away, and the latter would appear as a visual magnitude 2.7 star in the night sky of a hypothetical planet orbiting Procyon.
Procyon culminates at midnight on January 14. It forms one of the three vertices of the Winter Triangle asterism, in combination with Sirius and Betelgeuse. The prime period for evening viewing of Procyon is in late winter. The star has a color index of 0.42, and its hue has been described as having a faint yellow tinge to it.
Procyon’s orbit
Procyon is a binary star system with a bright primary component, Procyon A, having an apparent magnitude of 0.34, and a faint companion, Procyon B, at magnitude 10.7. The pair orbit each other with a period of 40.82 years along an elliptical orbit with an eccentricity of 0.407. The plane of their orbit is inclined at an angle of 31.1° to the line of sight with the Earth. The average separation of the two components is 15.0 AU, a little less than the distance between Uranus and the Sun, though the eccentric orbit carries them as close as 8.9 AU and as far as 21.0 AU.
The primary has a stellar classification of F5IV–V, indicating that it is a late-stage F-type main-sequence star. Procyon A is bright for its spectral class, suggesting that it is evolving into a subgiant that has nearly fused its core hydrogen into helium, after which it will expand as ‘burning’ moves outside the core. As it continues to expand, the star will eventually swell to about 80 to 150 times its current diameter and become a red or orange color. This will probably happen within 10 to 100 million years.
The effective temperature of the stellar atmosphere is an estimated 6,530 K, giving Procyon A a white hue. It is 1.5 times the solar mass, twice the solar radius (R☉), and has 6.9 times the Sun’s luminosity. Both the core and the envelope of this star are convective; the two regions being separated by a wide radiation zone.
Like Sirius B, Procyon’s companion is a white dwarf that was inferred from astrometric data long before it was observed. Its existence had been postulated by Friedrich Bessel as early as 1844, and, although its orbital elements had been calculated by Arthur Auwers in 1862, Procyon B was not visually confirmed until 1896 when John Martin Schaeberle observed it at the predicted position using the 36-inch refractor at Lick Observatory. It is more difficult to observe from Earth than Sirius B, due to a greater apparent magnitude difference and smaller angular separation from its primary.
Procyon B is considerably less massive than Sirius B; however, the peculiarities of degenerate matter ensure that it is larger than its more famous neighbor, with an estimated radius of 8,600 km, versus 5,800 km for Sirius B. The radius agrees with white dwarf models that assume a carbon core. It has a stellar classification of DQZ, having a helium-dominated atmosphere with traces of heavy elements. For reasons that remain unclear, the mass of Procyon B is unusually low for a white dwarf star of its type. With a surface temperature of 7,740 K, it is also much cooler than Sirius B; this is a testament to its lesser mass and greater age. The mass of the progenitor star for Procyon B was about 2.59 solar masses and it came to the end of its life some 1.19±0.11 Gyr ago, after a main-sequence lifetime of 680±170 Myr.
Life is unlikely around Procyon, because the habitable zone around 2.7 AU from the primary may not contain stable orbits, due to the white dwarf companion with a periastron of 8.9 AU. Also the white dwarf companion to Procyon would have stressed life severely during its red-giant phase. Procyon emits more of its light in the ultraviolet spectrum, which may be damaging to life. Still, life cannot be ruled out for other stars of the spectral type of Procyon, but such life would have a relatively short time to evolve and would face heavy bombardment from comets and meteorites as happened in the first few million years of the Earth’s existence. Shortly after the phase of heavy bombardment has ended for a planet orbiting a star like Procyon the star is likely to leave the main sequence preventing further development of life.
[https://en.wikipedia.org/wiki/Procyon]
Beta Canis Minoris has the traditional name Gomeisa, which comes from the Arabic ‘mirzam al-ghumaisa,’ ‘girdle of the bleary-eyed (woman).’ In Arabic, the short form ‘al-ghumaisa’ would be identical with the name of Procyon. In the night sky Gomeisa is notable for its proximity to the prominent star Procyon. The distance to this star is about 162 light-years (50 parsecs).
Gomeisa has an apparent visual magnitude of 2.89, making it easily visible to the naked eye. Beta Canis Minoris has about 3.5 times the Sun’s mass and is rotating rapidly with a projected rotational velocity of 210 km s−1, which gives a lower bound on the azimuthal rotational velocity along the star’s equator. The actual rotation rate may be about once per day.
The stellar classification of this star is B8 Ve. A luminosity class V star belongs on the main sequence, which means it is generating energy through the thermonuclear fusion of hydrogen at its core. The star is radiating this energy from its outer envelope at an effective temperature of 12,050 K, giving it a blue-white hue typical of B-type stars. An ‘e’ classification indicates that the spectrum contains emission lines, which means this is a Be star that is surrounded by a thin, circumstellar disk made of gaseous material ejected from the star. This hot, gaseous disk is about three times the radius of the star.
[https://en.wikipedia.org/wiki/Beta_Canis_Minoris]
In Bayer’s 1603 work Uranometria, Procyon is located on the dog’s belly, and Gomeisa on its neck. Gamma, Epsilon and Eta Canis Minoris lie nearby, marking the dog’s neck, crown and chest respectively. Although it has an apparent magnitude of 4.34, Gamma Canis Minoris is an orange K-type giant of spectral class K3-III C, which lies 318 light-years (97 parsecs) away. Its colour is obvious when seen through binoculars. It is a multiple system, consisting of the spectroscopic binary Gamma A and three optical companions, Gamma B, magnitude 13; Gamma C, magnitude 12; and Gamma D, magnitude 10. The two components of Gamma A orbit each other every 389.2 days, with an eccentric orbit that takes their separation between 2.3 and 1.4 astronomical units (AU).
Near Procyon, three stars share the name Delta Canis Minoris. Delta1 is a yellow-white F-type giant of magnitude 5.25 located around 790 light-years (240 parsecs) from Earth. About 360 times as luminous and 3.75 times as massive as the Sun, it is expanding and cooling as it ages, having spent much of its life as a main sequence star of spectrum B6V. Also known as 8 Canis Minoris, Delta2 is an F-type main-sequence star of spectral type F2V and magnitude 5.59 which is 136 light-years (42 parsecs) distant. The last of the trio, Delta3 (also known as 9 Canis Minoris), is a white main sequence star of spectral type A0Vnn and magnitude 5.83 which is 680 light-years (210 parsecs) distant. These stars mark the paws of the Lesser Dog’s left hind leg, while magnitude 5.13 Zeta marks the right. A blue-white bright giant of spectral type B8II, Zeta lies around 623 light-years (191 parsecs) away from the Solar System.
Lying approximately 264 light-years (81 parsecs) away with an apparent magnitude of 4.39, HD 66141 is 6.8 billion years old and has evolved into an orange giant of spectral type K2III with a diameter around 22 times that of the Sun, and weighing 1.1 solar masses. It is 174 times as luminous as the Sun, with an absolute magnitude of −0.15. HD 66141 was mistakenly named 13 Puppis, as its celestial coordinates were recorded incorrectly when catalogued and hence mistakenly thought to be in the constellation of Puppis; Bode gave it the name Lambda Canis Minoris, which is now obsolete. The orange giant is orbited by a planet, HD 66141b, which was detected in 2012 by measuring the star’s radial velocity. The planet has a mass around 6 times that of Jupiter and a period of 480 days.
Luyten’s Star (GJ 273) is a red dwarf in the constellation Canis Minor located at a distance of approximately 12.36 light-years (3.79 parsecs) from the Sun. It has a visual magnitude of 9.9, making it too faint to be viewed with the unaided eye. It is named after Willem Jacob Luyten, who, in collaboration with Edwin G. Ebbighausen, first determined its high proper motion in 1935.
This star is approximately a quarter the mass of the Sun and has 35% of the Sun’s radius. Luyten’s Star is at the maximum mass at which a red dwarf can be fully convective, which means that most if not all of the star forms an extended convection zone. It has a stellar classification of M3.5V, with the V luminosity class indicating this is a main-sequence star that is generating energy through the thermonuclear fusion of hydrogen at its core. The projected rotation rate of this star is too low to be measured, but is no greater than 1 km/s. Measurements of periodic variation in surface activity suggest a leisurely rotation period of roughly 116 days. The effective temperature of the star’s outer envelope is a relatively cool 3,150 K, giving the star the characteristic red-orange hue of an M-type star.
At present, Luyten’s Star is moving away from the Solar System. The closest approach occurred about 13,000 years ago when it came within 3.67 parsecs. The star is currently located 1.2 light years distant from Procyon, and the latter would appear as a visual magnitude −4.5 star in the night sky of a hypothetical planet orbiting Luyten’s Star. The closest encounter between the two stars occurred about 600 years ago when Luyten’s Star was at its minimal distance of about 1.12 ly from Procyon.
[https://en.wikipedia.org/wiki/Luyten%27s_Star]
The WZ Sagittae-type dwarf nova DY CMi (also known as VSX J074727.6+065050) flared up to magnitude 11.4 over January and February 2008 before dropping eight magnitudes to around 19.5 over approximately 80 days. It is a remote binary star system where a white dwarf and low mass star orbit each other close enough for the former star to draw material off the latter and form an accretion disc. This material builds up until it erupts dramatically.
A 12 arcmin wide region centered on the asterism NGC 2459
[http://cseligman.com/text/atlas/ngc24a.htm]
The Milky Way passes through much of Canis Minor, yet it has few deep-sky objects. William Herschel recorded four objects in his 1786 work Catalogue of Nebulae and Clusters of Stars, including two he mistakenly believed were star clusters. NGC 2459 is a group of five thirteenth- and fourteenth-magnitude stars that appear to lie close together in the sky but are not related. A similar situation has occurred with NGC 2394, also in Canis Minor. This is a collection of fifteen unrelated stars of ninth-magnitude and fainter;
NGC 2508
[http://www.davidcortner.com/slowblog/20140308.php]
Herschel also observed three faint galaxies, two of which are interacting with each other. NGC 2508 is a lenticular galaxy of thirteenth-magnitude, estimated at 205 million light-years (63 million parsecs) distance with a diameter of 80 thousand light-years (25 thousand parsecs). Named as a single object by Herschel, NGC 2402 is actually a pair of near-adjacent galaxies that appear to be interacting with each other. Only of fourteenth- and fifteenth-magnitudes respectively, the elliptical and spiral galaxy are thought to be approximately 245 million light-years distant, and each measure 55,000 light-years in diameter.
[http://www.constellationofthemonth.com/2014/10/canis-minor.html]
The 11 Canis-Minorids, also called the Beta Canis Minorids, are a meteor shower that arise near the fifth-magnitude star 11 Canis Minoris and were discovered in 1964 by Keith Hindley, who investigated their trajectory and proposed a common origin with the comet D/1917 F1 Mellish. However, this conclusion has been refuted subsequently as the number of orbits analyzed was low and their trajectories too disparate to confirm a link. They last from 4 to 15 December, peaking over 10 and 11 December.
[https://en.wikipedia.org/wiki/Canis_Minor]
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