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ANDROMEDA   AQUARIUS   AQUILA   ARIES   AURIGA   BOOTES   CAMELOPARDALIS   CANCER   CANES VENATICI   CANIS MAJOR   CANIS MINOR   CAPRICORNUS   CARINA   CASSIOPEIA   CENTAURUS   CEPHEUS   CETUS   COLUMBA   COMA BERENICES   CORONA AUSTRALIS   CORONA BOREALIS   CORVUS   CRATER   CRUX   CYGNUS   DELPHINUS   DORADO   DRACO   EQUULEUS   ERIDANUS   FORNAX   GEMINI   HERCULES   HYDRA   LACERTA   LEO   LEO MINOR   LEPUS   LIBRA   LUPUS   LYNX   LYRA   MONOCEROS   OPHIUCHUS   ORION   PEGASUS   PERSEUS   PISCES   PISCIS AUSTRALIS   PUPPIS   SAGITTA   SAGITTARIUS   SCORPIUS   SCULPTOR   SCUTUM   SERPENS   SEXTANS   TAURUS   TRIANGULUM   TUCANA   URSA MAJOR   URSA MINOR   VELA   VIRGO   VULPECULA  

CANIS MAJOR

The Big Dog


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Canis Major - Celestial Atlas by Alexander Jamieson - 1822

Following faithfully at Orion's heels is Canis Major, the big dog. Part of the Orion family of constellations, it represents the larger of Orion's two hunting dogs. It is a constellation that has had a lot of attention throughout history from cultures all over the world, because it contains far and away the brightest star in the entire night sky - Sirius, the Dog Star. With a magnitude of -1.46, it is more than twice as bright as the next brightest star, magnitude -0.72 Canopus.

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Orion Family - February 1, 10:00 PM - Latitude 45° North, Longitude 95° West





Stars of Canis Major

Sirius - The Dog Star (RA: 06h45m08.341s DE:-1643'16.56")

In ancient Egypt, Sirius was revered as the Nile Star, or the Star of Isis. Some Egyptian temples were aligned with window openings facing east, directly where the Dog Star rose, and when the light from the star shone through the opening, it meant the Nile was about to commence its annual flood, spreading its waters and rich soil over the adjoining floodplain, an occurrence critical to the survival of the Egyptian people. Some ancient Mayan temples as well were aligned with Sirius, as it signaled the advent of the all important rainy season.

By the time the hot days of July and August arrive, Sirius is rising with the Sun, and the "dog days of summer" are upon us. In ancient times it was thought the energy of Sirius combined with the Sun at this time, and the star was blamed, in the words of Robert Burnham Jr., for "bringing forth fever in men and madness in dogs."

Dante spoke of "the great scourge of days canicular".

Virgil wrote, "the Dog Star, that burning constellation, when he brings drought and diseases on sickly mortals, rises and saddens the sky with inauspicious light".

Even in Homer's Illiad, we read of the wrathful Achilles "blazing as the star that cometh forth at Harvest-time, shining forth amid the host of stars in the darkness of the night, the star whose name men call Orion's Dog. Brightest of all is he, yet for an evil sign is he set, and bringeth much fever upon hapless men..."

The name Sirius is Greek for scorching. It is an A1V blue/white main sequence star, 1.8 times the diameter of the Sun. The reason it is so bright is because it is so close, only 8.7 light years away, the second closest naked eye star to Earth (after Alpha Centauri), and the fifth closest star overall. Because Sirius is so bright, when it is close to the horizon, it puts on quite a show, atmospheric refraction turning it into a wild kaleidoscope of dazzling, sparkling colors.

In 1862 Sirius was discovered to have a tiny white dwarf companion star, dubbed Sirius B, or The Pup. You can see the little dwarf as a small white dot in the lower left of the Hubble image below.

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Sirius and Sirius B - Hubble Space Telescope - December, 2005

Although Sirius is unmistakably blue/white in colour, nearly all ancient texts refer to it as red. Some suggest that colours were sometimes interpreted differently in ancient times. But another possible explanation surfaced with the 1862 discovery of the tiny companion star to Sirius, Sirius B, which is a white dwarf. A white dwarf is the evolutionary descendent of a red giant, leading to the speculation that in ancient times Sirius B was in fact a red giant that overshadowed Sirius, accounting for the red colour. The problem is that it should normally take at least 100,000 years for a red giant to become a white dwarf, so the colour discrepancy remains a mystery.

In 1976 American author Robert Temple wrote a controversial best selling book called The Sirius Mystery, claiming that the primitive Dogon tribe of Mali, West Africa, possessed knowledge of the existence of Sirius B, and many of its characteristics. Since Sirius B is far beyond naked eye visibility, the book suggests this knowledge was imparted to the Dogon when they were visited by aliens who lived in the Sirius star system. Scientists world wide were quick to analyze his data and his theories, and most, including legendary astronomer Carl Sagan, found them wanting. Famed British astronomer Ian Ridpath conducted an excellent in depth study of Temple's theories called Investigating The Sirius Mystery.

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Murzim (RA: 06h22m41.982s DE:-1757'21.32")

Beta Canis Majoris is named Murzim, Arabic for the announcer, as it precedes Sirius across the sky, heralding the appearance of the great dog star. It is a B1III blue giant, also classified as a Beta Cephei variable, a star with a small but regular variability. It has a magnitude of 2.0 and is 500 light years away.

Muliphen (RA: 07h03m45.493s DE:-1537'59.99")

Gamma Canis Majoris is named Muliphen (or Muliphien), from the Arabic "Al Muhlifein," an ancient title that has been applied (with various spellings) to different stars and groups of stars through the ages. Its modern translation eludes even Allen, but seems to involve an ancient Arabic profanity towards stars that are not what they appear to be. How it came to be applied to dim little Gamma Canis Majoris is anybody's guess, perhaps for the same mysterious reason the faint star was allotted the high Bayer ranking of Gamma. From a great distance of 441 light years, the B6III blue giant can only manage a magnitude of 4.11.

Adara (RA: 06h58m37.552s DE:-2858'19.50")

With a magnitude of 1.5, Epsilon Canis Majoris is the second brightest star in the constellation. It's named Adara (or Adhara), from the Arabic "Aoul al Adzari", first of the virgins, as along with Wezen, Aludra and Thanih al Adzari, it forms an ancient Arabic grouping called "Al Adhara", The Virgins. It is a B1III blue giant, 450 light years away.

Thanih al Adzari (RA: 07h03m01.470s DE:-2349'59.79")

Omicron(2) Canis Majoris has the Arabic name Thanih al Adzari, second of the virgins. It is a B4I blue supergiant, so luminous that even at the very great distance of 2,800 light years, it's still bright enough to shine in our sky with a magnitude of 3.04.

Aludra (RA: 07h24m05.698s DE:-2918'11.09")

Eta Canis Majoris is Aludra, Arabic for the virgin. It is a B5I blue supergiant, another super luminous star that manages to shine brightly at magnitude 2.4, even though it is 2,000 light years away.

Wezen (RA: 07h08m23.481s DE:-2623'35.48")

The fourth virgin is Delta Canis Majoris, named Wezen, Arabic for weight, to which R.H. Allen adds, "as the star seems to rise with difficulty from the horizon"; but Ideler justly calls this an astonishing star-name." It is an F8I yellow supergiant, yet another star with impressive luminosity, shining at magnitude 1.8 from 1,800 light years away, making it the third brightest star in the constellation.

Furud (RA: 06h20m18.800s DE:-3003'48.06")

Zeta Canis Majoris is known as Furud, the solitary one. It is a spectroscopic binary, 360 light years away. The primary star is a B2V blue main sequence star, with a magnitude of 3.0.

VY Canis Majoris - HD 58061 (RA: 07h22m58.327s DE:-2546'03.40")

Before we leave the stars of Canis Major, there is one more to take note of. Although it is unnamed and well beyond naked visibility, it is one of the largest stars ever discovered. Designated VY Canis Majoris, it has a diameter of over 1 billion miles (compared to our Sun's diameter of only 1 million miles), and classified as an M30 red hypergiant nearing the end of its life, and beginning to surround itself with a nebula of expelled gases, as shown in the Hubble image below.

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VY Canis Majoris - M3 Red Hypergiant - Hubble Space Telescope - January, 2007

Planets of Canis Major

NU02 Canis Majoris - 7 Canis Majoris - HD 47205 (RA: 06h36m41.105s DE:-1915'22.23")

Canis Major contains eight stars known to support planetary systems. NU02 Canis Majoris is bright enough at magnitude 3.95 to be easily seen with the naked eye. Classified as a K1III yellow/orange giant, it has a gas giant planet in orbit around it 2.6 times the size of Jupiter. The planet, 7 CMa b, is about twice as far from its sun as Earth (1.9 AU), and takes about twice as long to complete one orbit (763 days). It is the closest known planetary system in Canis Major, about 65 light years away.

HD 45364 (RA: 06h25m38.538s DE:-3128'51.64")

Almost twice as far at 106 light years is HD 45364, a G8V yellow main sequence star similar to our Sun. Beyond naked eye visibility at magnitude 8.08, it has two known planets. HD 45364 b, which is only 0.19 times the mass of Jupiter and approaching super earth size, is about 63 million miles (100 million kms) from the star and takes 227 days to complete one orbit. HD 45364 c is 0.66 times the mass of Jupiter, in a 343 day orbit, 83 million miles (133 million kms) from the star.

HD 47186 (RA: 06h36m08.811s DE:-2737'24.26")

A little farther away at 123 light years and still beyond naked eye visibility at magnitude 7.63 is HD 47186, a G6V yellow main sequence star, very like our Sun, which also has two known planets. HD 47186 b is a super earth, about 20 times the mass of our planet. Unfortunately it is dangerously close to its parent star, only 4.6 million miles, taking only 4 days to complete an orbit, and presumably far too hot to support life. HD 47186 c is about a third (0.35) the size of Jupiter, in a 1,354 day orbit, 223 million miles (357 million kms) from the star.

The remaining five stars known to host planets in Canis Major are all very dim and far away, and the planets are all large gas giants. For more information on these and other exoplanets, visit NASA's New Worlds Atlas, and The Open Exoplanets Catalogue.



Deep Skies of Canis Major

M41 - NGC 2287 (RA: 06h46m00.0s DE:-2045'00")

Just below Sirius is the bright open star cluster M41 (NGC 2287). At magnitude 4.5 it is visible to the naked eye, and a good target for backyard telescopes. Containing about 100 stars, the cluster is 2,300 light years away.

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M41 (NGC 2287) - Open Star Cluster - Atlas Image 2MASS/UMass/IPAC-Caltech/NASA/NSF.

NGC 2362 - Tau Canis Majoris Cluster (RA: 07h18m 42.0s DE:-2457'00")

Open star cluster NGC 2362 is also visible to the naked eye at magnitude 4.1. The bright central star is Tau Canis Majoris, and the grouping is often referred to as the Tau Canis Majoris Cluster. It is one of the largest open clusters, estimated to contain about 500 stars, about 4,000 light years away.

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NGC 2362 - Spitzer Space Telescope - Infrared - January, 2009

NGC 2359 - Thor's Helmet (RA: 07h18m 30.0s DE:-1314'00")

NGC 2359 is an emission nebula, given the name Thor's Helmet. It is 30 light years across, located about 15,000 light years away, with a magnitude around 10.

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NGC 2359 - Thor's Helmet - European Southern Observatory - October, 2012

A closeup of the central region of NGC 2359 reveals the giant Wolf Rayet star HD 56925, very bright in the left centre of the image below. The star is nearing the end of its life, casting off its outside layers before it goes supernova.

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NGC 2359 - Central Region - European Southern Observatory - October, 2012

ESO 489-056 Dwarf Galaxy (RA: 06h26m 17.0s DE:-2615'56")

Looking outside our galaxy, the first object of interest is ESO 489-056, a dwarf galaxy 16 million light years away containing about one billion stars. The merging spiral galaxies that appear to be part of the lower left corner of the dwarf galaxy are merely in the same line of sight and are actually many millions of light years behind it. With a magnitude of 14.7, the dwarf galaxy is only visible in large telescopes. It should not be confused with the Canis Major Dwarf Galaxy, a controversial name given to an dense collection of stars hidden behind dust clouds deep inside the Milky Way.

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ESO 489-056 - Dwarf Galaxy - Hubble Space Telescope - August, 2013

NGC 2217 (RA: 06h21m 42.0s DE:-2714'00")

Much farther away at 65 million light years is NGC 2217, a spiral galaxy with a prominent central bar, and a magnitude of 10.4.

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NGC 2217 - Barred Spiral Galaxy - European Southern Observatory - January, 2012

NGC 2280 (RA: 06h44m 48.0s DE:-2738'00")

Farther still at 75 million light-years is NGC 2280, a spiral galaxy with a magnitude of 11.0.

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NGC 2280 - Spiral Galaxy - European Southern Observatory - December, 2009

NGC 2207 and IC 2163 (RA: 06h16m 24.0s DE:-2122'00"")

Finally we have a pair of merging galaxies out at a distance of 86 million light years. The large spiral galaxy, NGC 2207, is in the process of assimilating the smaller spiral galaxy, IC 2163. The pair have a combined magnitude of 10.2.

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NGC 2207 - Merging Galaxies - Hubble Space Telescope - November, 1999







Winter: Orion   Canis Major   Canis Minor   Monoceros   Lepus   Eridanus   Taurus   Auriga   Camelopardalis   Lynx   Gemini   Cancer  
Spring: Hydra   Sextans   Crater   Corvus   Leo   Leo Minor   Ursa Major   Ursa Minor   Canes Venatici   Coma Berenices   Virgo   Bootes  
Summer: Draco   Corona Borealis   Hercules   Ophiuchus   Serpens   Libra   Scorpius   Sagittarius   Scutum   Aquila   Sagitta   Vulpecula   Lyra   Cygnus  
Autumn: Andromeda   Perseus   Pegasus   Cassiopeia   Cepheus   Cetus   Lacerta   Delphinus   Equuleus   Capricornus   Aquarius   Pisces   Aries   Triangulum  
Southern Skies: Centaurus   Crux   Lupus   Corona Australis   Piscis Australis   Sculptor   Tucana   Fornax   Dorado   Columba   Puppis   Carina   Vela  

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