Sirius

Sirius

Overview
Sirius is the brightest star in the night sky. With a visual apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 of −1.46, it is almost twice as bright as Canopus
Canopus
Canopus |Alpha]] Carinae) is the brightest star in the southern constellation of Carina and Argo Navis, and the second brightest star in the night-time sky, after Sirius. Canopus's visual magnitude is −0.72, and it has an absolute magnitude of −5.53.Canopus is a supergiant of spectral...

, the next brightest star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

. The name "Sirius" is derived from the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

: Seirios ("glowing" or "scorcher"). The star has the Bayer designation
Bayer designation
A Bayer designation is a stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellation's Latin name...

 Alpha
Alpha (letter)
Alpha is the first letter of the Greek alphabet. In the system of Greek numerals it has a value of 1. It was derived from the Phoenician letter Aleph...

 Canis Major
Canis Major
Canis Major is one of the 88 modern constellations, and was included in the 2nd-century astronomer Ptolemy's 48 constellations. Its name is Latin for 'greater dog', and is commonly represented as one of the dogs following Orion the hunter...

is (α CMa). What the naked eye perceives as a single star is actually a binary star
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

 system, consisting of a white main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...

 star of spectral type A1V, termed Sirius A, and a faint white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...

 companion of spectral type DA2, termed Sirius B.
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Encyclopedia
Sirius is the brightest star in the night sky. With a visual apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 of −1.46, it is almost twice as bright as Canopus
Canopus
Canopus |Alpha]] Carinae) is the brightest star in the southern constellation of Carina and Argo Navis, and the second brightest star in the night-time sky, after Sirius. Canopus's visual magnitude is −0.72, and it has an absolute magnitude of −5.53.Canopus is a supergiant of spectral...

, the next brightest star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

. The name "Sirius" is derived from the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

: Seirios ("glowing" or "scorcher"). The star has the Bayer designation
Bayer designation
A Bayer designation is a stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellation's Latin name...

 Alpha
Alpha (letter)
Alpha is the first letter of the Greek alphabet. In the system of Greek numerals it has a value of 1. It was derived from the Phoenician letter Aleph...

 Canis Major
Canis Major
Canis Major is one of the 88 modern constellations, and was included in the 2nd-century astronomer Ptolemy's 48 constellations. Its name is Latin for 'greater dog', and is commonly represented as one of the dogs following Orion the hunter...

is (α CMa). What the naked eye perceives as a single star is actually a binary star
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

 system, consisting of a white main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...

 star of spectral type A1V, termed Sirius A, and a faint white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...

 companion of spectral type DA2, termed Sirius B. The distance separating Sirius A from its companion varies between 8.1 and 31.5 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....

.

Sirius appears bright because of both its intrinsic luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...

 and its proximity to Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

. At a distance of 2.6 parsec
Parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....

s (8.6 ly
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...

), the Sirius system is one of Earth's near neighbors; for Northern-hemisphere observers between 30 degrees and 73 degrees of latitude (including almost all of Europe and North America), it is the closest star (after the Sun) that can be seen with a naked eye. Sirius A is about twice as massive as the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 and has an absolute visual magnitude
Absolute magnitude
Absolute magnitude is the measure of a celestial object's intrinsic brightness. it is also the apparent magnitude a star would have if it were 32.6 light years away from Earth...

 of 1.42. It is 25 times more luminous than the Sun but has a significantly lower luminosity than other bright stars such as Canopus or Rigel
Rigel
Rigel is the brightest star in the constellation Orion and the sixth brightest star in the sky, with visual magnitude 0.18...

. The system is between 200 and years old. It was originally composed of two bright bluish stars. The more massive of these, Sirius B, consumed its resources and became a red giant
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...

 before shedding its outer layers and collapsing into its current state as a white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...

 around years ago.

Sirius is also known colloquially as the "Dog Star", reflecting its prominence in its constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

, Canis Major
Canis Major
Canis Major is one of the 88 modern constellations, and was included in the 2nd-century astronomer Ptolemy's 48 constellations. Its name is Latin for 'greater dog', and is commonly represented as one of the dogs following Orion the hunter...

 (Greater Dog). The heliacal rising
Heliacal rising
The heliacal rising of a star occurs when it first becomes visible above the eastern horizon for a brief moment just before sunrise, after a period of time when it had not been visible....

 of Sirius marked the flooding of the Nile in Ancient Egypt
Ancient Egypt
Ancient Egypt was an ancient civilization of Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. Egyptian civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh...

 and the "dog days
Dog Days
"Dog Days" are the hottest, most sultry days of summer. In the Northern Hemisphere, the dog days of summer are most commonly experienced in the months of July and August, which typically observe the warmest summer temperatures. In the Southern Hemisphere, they typically occur in January and...

" of summer for the ancient Greeks
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

, while to the Polynesians it marked winter and was an important star for navigation around the Pacific Ocean.

Observational history


X1:N14-M44
Hieroglyph of
Sirius/Sopdet

Sirius, known in ancient Egypt
Ancient Egypt
Ancient Egypt was an ancient civilization of Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. Egyptian civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh...

 as Sopdet (Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

: Sothis
Sothis
Sothis is the name of a star that the Egyptians considered unusually significant. The star is not explicitly identified, but there are enough clues for modern scholars to be almost unanimous in identifying Sothis as Sirius....

), is recorded in the earliest astronomical
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...

 records. During the era of the Middle Kingdom
Middle Kingdom of Egypt
The Middle Kingdom of Egypt is the period in the history of ancient Egypt stretching from the establishment of the Eleventh Dynasty to the end of the Fourteenth Dynasty, between 2055 BC and 1650 BC, although some writers include the Thirteenth and Fourteenth dynasties in the Second Intermediate...

, Egyptians based their calendar
Egyptian calendar
The ancient civil Egyptian calendar had a year that was 360 days long and was divided into 12 months of 30 days each, plus five extra days at the end of the year. The months were divided into three weeks of ten days each...

 on the heliacal rising
Heliacal rising
The heliacal rising of a star occurs when it first becomes visible above the eastern horizon for a brief moment just before sunrise, after a period of time when it had not been visible....

 of Sirius, namely the day it becomes visible just before sunrise after moving far enough away from the glare of the Sun. This occurred just before the annual flooding of the Nile
Nile
The Nile is a major north-flowing river in North Africa, generally regarded as the longest river in the world. It is long. It runs through the ten countries of Sudan, South Sudan, Burundi, Rwanda, Democratic Republic of the Congo, Tanzania, Kenya, Ethiopia, Uganda and Egypt.The Nile has two major...

 and the summer solstice
Solstice
A solstice is an astronomical event that happens twice each year when the Sun's apparent position in the sky, as viewed from Earth, reaches its northernmost or southernmost extremes...

, after a 70-day absence from the skies. The hieroglyph for Sothis features a star and a triangle. Sothis was identified with the great goddess Isis
Isis
Isis or in original more likely Aset is a goddess in Ancient Egyptian religious beliefs, whose worship spread throughout the Greco-Roman world. She was worshipped as the ideal mother and wife as well as the matron of nature and magic...

, who formed a part of a trinity with her husband Osiris
Osiris
Osiris is an Egyptian god, usually identified as the god of the afterlife, the underworld and the dead. He is classically depicted as a green-skinned man with a pharaoh's beard, partially mummy-wrapped at the legs, wearing a distinctive crown with two large ostrich feathers at either side, and...

 and their son Horus
Horus
Horus is one of the oldest and most significant deities in the Ancient Egyptian religion, who was worshipped from at least the late Predynastic period through to Greco-Roman times. Different forms of Horus are recorded in history and these are treated as distinct gods by Egyptologists...

, while the 70-day period symbolised the passing of Isis and Osiris through the duat
Duat
In Egyptian mythology, Duat is the underworld. The Duat is a vast area under the Earth, connected with Nun, the waters of the primordial abyss. The Duat is the realm of the god Osiris and the residence of other gods and supernatural beings...

(Egyptian underworld).

The ancient Greeks observed that the appearance of Sirius heralded the hot and dry summer, and feared that it caused plants to wilt, men to weaken, and women to become aroused. Due to its brightness, Sirius would have been noted to twinkle
Scintillation (astronomy)
Scintillation or twinkling are generic terms for rapid variations in apparent brightness or color of a distant luminous object viewed through a medium, most commonly the atmosphere ....

 more in the unsettled weather conditions of early summer. To Greek observers, this signified certain emanations which caused its malignant influence. People suffering its effects were said to be astroboletos (αστροβολητος) or "star-struck". It was described as "burning" or "flaming" in literature. The season following the star's appearance came to be known as the Dog Days of summer. The inhabitants of the island of Ceos
Kea (island)
Kea , also known as Gia or Tzia , Zea, and, in Antiquity, Keos , is an island of the Cyclades archipelago, in the Aegean Sea, in Greece. Kea is part of the Kea-Kythnos peripheral unit. Its capital, Ioulis, is inland at a high altitude and is considered quite picturesque...

 in the Aegean Sea
Aegean Sea
The Aegean Sea[p] is an elongated embayment of the Mediterranean Sea located between the southern Balkan and Anatolian peninsulas, i.e., between the mainlands of Greece and Turkey. In the north, it is connected to the Marmara Sea and Black Sea by the Dardanelles and Bosporus...

 would offer sacrifices to Sirius and Zeus
Zeus
In the ancient Greek religion, Zeus was the "Father of Gods and men" who ruled the Olympians of Mount Olympus as a father ruled the family. He was the god of sky and thunder in Greek mythology. His Roman counterpart is Jupiter and his Etruscan counterpart is Tinia.Zeus was the child of Cronus...

 to bring cooling breezes, and would await the reappearance of the star in summer. If it rose clear, it would portend good fortune; if it was misty or faint then it foretold (or emanated) pestilence. Coins retrieved from the island from the 3rd century BC feature dogs or stars with emanating rays, highlighting Sirius' importance. The Romans celebrated the heliacal setting of Sirius around April 25, sacrificing a dog, along with incense, wine, and a sheep, to the goddess Robigo so that the star's emanations would not cause wheat rust
Rust (fungus)
Rusts are plant diseases caused by pathogenic fungi of the order Pucciniales. About 7800 species are known. Rusts can affect a variety of plants; leaves, stems, fruits and seeds. Rust is most commonly seen as coloured powder, composed off tiny aeciospores which land on vegetation producing...

 on wheat crops that year.

Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

 of Alexandria mapped the stars in Books VII and VIII of his Almagest
Almagest
The Almagest is a 2nd-century mathematical and astronomical treatise on the apparent motions of the stars and planetary paths. Written in Greek by Claudius Ptolemy, a Roman era scholar of Egypt,...

, in which he used Sirius as the location for the globe's central meridian. He curiously depicted it as one of six red-coloured stars (see the Red controversy section below). The other five are class M and K stars, such as Arcturus and Betelgeuse
Betelgeuse
Betelgeuse, also known by its Bayer designation Alpha Orionis , is the eighth brightest star in the night sky and second brightest star in the constellation of Orion, outshining its neighbour Rigel only rarely...

.

Bright stars were important to the ancient Polynesians
Polynesian culture
Polynesian culture refers to the indigenous peoples' culture of Polynesia who share common traits in language, customs and society. Chronologically, the development of Polynesian culture can be divided into four different historical eras:...

 for navigation between the many islands and atolls of the Pacific Ocean. Low on the horizon, they acted as stellar compasses to assist mariners in charting courses to particular destinations. They also served as latitude markers; the declination of Sirius matches the latitude of the archipelago of Fiji
Fiji
Fiji , officially the Republic of Fiji , is an island nation in Melanesia in the South Pacific Ocean about northeast of New Zealand's North Island...

 at 17°S and thus passes directly over the islands each night. Sirius served as the body of a "Great Bird" constellation called Manu, with Canopus
Canopus
Canopus |Alpha]] Carinae) is the brightest star in the southern constellation of Carina and Argo Navis, and the second brightest star in the night-time sky, after Sirius. Canopus's visual magnitude is −0.72, and it has an absolute magnitude of −5.53.Canopus is a supergiant of spectral...

 as the southern wingtip and Procyon
Procyon
Procyon is the brightest star in the constellation Canis Minor. To the naked eye, it appears to be a single star, the seventh brightest in the night sky with a visual apparent magnitude of 0.34...

 the northern wingtip, which divided the Polynesian night sky into two hemispheres. Just as the appearance of Sirius in the morning sky marked summer in Greece, so it marked the chilly onset of winter for the Māori, whose name Takurua described both the star and the season. Its culmination at the winter solstice
Winter solstice
Winter solstice may refer to:* Winter solstice, astronomical event* Winter Solstice , former band* Winter Solstice: North , seasonal songs* Winter Solstice , 2005 American film...

 was marked by celebration in Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

, where it was known as Ka'ulua, "Queen of Heaven". Many other Polynesian names have been recorded, including Tau-ua in the Marquesas Islands
Marquesas Islands
The Marquesas Islands enana and Te Fenua `Enata , both meaning "The Land of Men") are a group of volcanic islands in French Polynesia, an overseas collectivity of France in the southern Pacific Ocean. The Marquesas are located at 9° 00S, 139° 30W...

, Rehua in New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

, and Aa and Hoku-Kauopae in Hawaii.

Kinematics


In 1718, Edmond Halley
Edmond Halley
Edmond Halley FRS was an English astronomer, geophysicist, mathematician, meteorologist, and physicist who is best known for computing the orbit of the eponymous Halley's Comet. He was the second Astronomer Royal in Britain, following in the footsteps of John Flamsteed.-Biography and career:Halley...

 discovered the proper motion
Proper motion
The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system. It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree. This contrasts with radial velocity, which is the time rate of change in...

 of the hitherto presumed "fixed" stars after comparing contemporary astrometric
Astrometry
Astrometry is the branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. The information obtained by astrometric measurements provides information on the kinematics and physical origin of our Solar System and our Galaxy, the Milky...

 measurements with those given in Ptolemy's Almagest. The bright stars Aldebaran
Aldebaran
Aldebaran is a red giant star located about 65 light years away in the zodiac constellation of Taurus. With an average apparent magnitude of 0.87 it is the brightest star in the constellation and is one of the brightest stars in the nighttime sky...

, Arcturus and Sirius were noted to have moved significantly, the last of which having progressed 30 arc minutes
Minute of arc
A minute of arc, arcminute, or minute of angle , is a unit of angular measurement equal to one sixtieth of one degree. In turn, a second of arc or arcsecond is one sixtieth of one minute of arc....

 (about the diameter of the moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

) southwards in 1,800 years.

In 1868, Sirius became the first star to have its velocity measured. Sir William Huggins
William Huggins
Sir William Huggins, OM, KCB, FRS was an English amateur astronomer best known for his pioneering work in astronomical spectroscopy.-Biography:...

 examined the spectrum of this star and observed a noticeable red shift
Red shift
-Science:* Redshift, the increase of wavelength of detected electromagnetic radiation with respect to the original wavelength of the emission* Red shift, an informal term for a bathochromic shift...

. He concluded that Sirius was receding from the Solar System at about 40 km/s. Compared to the modern value of −7.6 km/s, this both was an overestimate and had the wrong sign; the minus means it is approaching the Sun. However, it is notable for introducing the study of celestial radial velocities
Radial velocity
Radial velocity is the velocity of an object in the direction of the line of sight . In astronomy, radial velocity most commonly refers to the spectroscopic radial velocity...

.

Discovery of a companion


In 1844 German astronomer Friedrich Bessel
Friedrich Bessel
-References:* John Frederick William Herschel, A brief notice of the life, researches, and discoveries of Friedrich Wilhelm Bessel, London: Barclay, 1847 -External links:...

 deduced from changes in the proper motion of Sirius that it had an unseen companion. Nearly two decades later, on January 31, 1862, American telescope-maker and astronomer Alvan Graham Clark
Alvan Graham Clark
Alvan Graham Clark , born in Fall River, Massachusetts, was an American astronomer and telescope-maker. He was the son of Alvan Clark, founder of Alvan Clark & Sons....

 first observed the faint companion, which is now called Sirius B, or affectionately "the Pup". This happened during testing of a 18.5 inches (469.9 mm) aperture great refractor
Great refractor
Great refractor refers to a large telescope with a lens, usually the largest refractor at an observatory with an equatorial mount. The preeminence and success of this style in observational astronomy was an era in telescope use in the 19th and early 20th century. Great refractors were large...

 telescope for Dearborn Observatory
Dearborn Observatory
The Dearborn Observatory is an astronomical observatory located on the Evanston campus of Northwestern University. The observatory was originally constructed in 1888...

, which was the largest refracting telescope lens in existence at the time, and the largest telescope in America.

The visible star is now sometimes known as Sirius A. Since 1894, some apparent orbital irregularities in the Sirius system have been observed, suggesting a third very small companion star, but this has never been definitely confirmed. The best fit to the data indicates a six-year orbit around Sirius A and a mass of only 0.06 solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...

es. This star would be five to ten magnitudes fainter than the white dwarf Sirius B, which would account for the difficulty of observing it. Observations published in 2008 were unable to detect either a third star or a planet. An apparent "third star" observed in the 1920s is now confirmed as a background object.

In 1915, Walter Sydney Adams
Walter Sydney Adams
Walter Sydney Adams was an American astronomer.-Life and work:He was born in Antioch, Syria to missionary parents, and was brought to the U.S. in 1885 He graduated from Dartmouth College in 1898, then continued his education in Germany...

, using a 60-inch (1.5 m) reflector at Mount Wilson Observatory
Mount Wilson Observatory
The Mount Wilson Observatory is an astronomical observatory in Los Angeles County, California, United States. The MWO is located on Mount Wilson, a 5,715 foot peak in the San Gabriel Mountains near Pasadena, northeast of Los Angeles...

, observed the spectrum
Spectrum
A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...

 of Sirius B and determined that it was a faint whitish star. This led astronomers to conclude that it was a white dwarf, the second to be discovered. The diameter of Sirius A was first measured by Robert Hanbury Brown
Robert Hanbury Brown
Robert Hanbury Brown, AC FRS was a British astronomer and physicist born in Aruvankadu, India. He made notable contributions to the development of radar and he later conducted pioneering work in the field of radio astronomy...

 and Richard Q. Twiss
Richard Q. Twiss
Richard Q. Twiss is famous for his work on the Hanbury-Brown and Twiss effect with Robert Hanbury Brown. This led to the development of the Hanbury Brown-Twiss intensity interferometer in the UK in 1954. Their work was controversial as it appeared to contradict the established beliefs about...

 in 1959 at Jodrell Bank
Jodrell Bank
The Jodrell Bank Observatory is a British observatory that hosts a number of radio telescopes, and is part of the Jodrell Bank Centre for Astrophysics at the University of Manchester...

 using their stellar intensity interferometer
Intensity interferometer
An intensity interferometer is the name given to devices that use the Hanbury-Brown and Twiss effect. In astronomy, the most common use of such an astronomical interferometer is to determine the apparent angular diameter of a radio source or star...

. In 2005, using the Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...

, astronomers determined that Sirius B has nearly the diameter of the Earth, 12000 kilometres (7,456.5 mi), with a mass that is 98% of the Sun.

Red controversy


Around 150 AD, the Hellenistic astronomer Claudius Ptolemy described Sirius as reddish, along with five other stars, Betelgeuse
Betelgeuse
Betelgeuse, also known by its Bayer designation Alpha Orionis , is the eighth brightest star in the night sky and second brightest star in the constellation of Orion, outshining its neighbour Rigel only rarely...

, Antares
Antares
Antares is a red supergiant star in the Milky Way galaxy and the sixteenth brightest star in the nighttime sky . Along with Aldebaran, Spica, and Regulus it is one of the four brightest stars near the ecliptic...

, Aldebaran
Aldebaran
Aldebaran is a red giant star located about 65 light years away in the zodiac constellation of Taurus. With an average apparent magnitude of 0.87 it is the brightest star in the constellation and is one of the brightest stars in the nighttime sky...

, Arcturus and Pollux
Pollux (star)
Pollux is an orange giant star approximately 34 light-years from the Earth in the constellation of Gemini . Pollux is the brightest star in the constellation, brighter than Castor...

, all of which are clearly of orange or red hue. The discrepancy was first noted by amateur astronomer Thomas Barker, squire of Lyndon Hall
Lyndon, Rutland
Lyndon is a small village in the county of Rutland in the East Midlands of England.Thomas Barker of Lyndon Hall kept a detailed weather record from 1736 to 1798. William Whiston , best known for his translation of Josephus, died at the Hall, the home of his son-in-law, Samuel Barker on 22 August...

 in Rutland
Rutland
Rutland is a landlocked county in central England, bounded on the west and north by Leicestershire, northeast by Lincolnshire and southeast by Peterborough and Northamptonshire....

, who prepared a paper and spoke at a meeting of the Royal Society in London in 1760. The existence of other stars changing in brightness gave credence to the idea that some may change in colour too; Sir John Herschel noted this in 1839, possibly influenced by witnessing Eta Carinae two years earlier. Thomas Jefferson Jackson See
Thomas Jefferson Jackson See
Thomas Jefferson Jackson See, was an American astronomer of high potential who ended a colorful life with no real accomplishment in astronomy or physics...

 resurrected discussion on red Sirius with the publication of several papers in 1892, and a final summary in 1926. He cited not only Ptolemy but also the poet Aratus
Aratus
Aratus was a Greek didactic poet. He is best known today for being quoted in the New Testament. His major extant work is his hexameter poem Phaenomena , the first half of which is a verse setting of a lost work of the same name by Eudoxus of Cnidus. It describes the constellations and other...

, the orator Cicero
Cicero
Marcus Tullius Cicero , was a Roman philosopher, statesman, lawyer, political theorist, and Roman constitutionalist. He came from a wealthy municipal family of the equestrian order, and is widely considered one of Rome's greatest orators and prose stylists.He introduced the Romans to the chief...

, and general Germanicus
Germanicus
Germanicus Julius Caesar , commonly known as Germanicus, was a member of the Julio-Claudian dynasty and a prominent general of the early Roman Empire. He was born in Rome, Italia, and was named either Nero Claudius Drusus after his father or Tiberius Claudius Nero after his uncle...

 as colouring the star red, though acknowledging that none of the latter three authors were astronomers, the last two merely translating Aratus' poem Phaenomena. Seneca
Seneca the Younger
Lucius Annaeus Seneca was a Roman Stoic philosopher, statesman, dramatist, and in one work humorist, of the Silver Age of Latin literature. He was tutor and later advisor to emperor Nero...

, too, had described Sirius as being of a deeper red colour than Mars. However, not all ancient observers saw Sirius as red. The 1st century AD poet Marcus Manilius
Marcus Manilius
Marcus Manilius was a Roman poet, astrologer, and author of a poem in five books called Astronomica.-Criticism:The author of Astronomica is neither quoted nor mentioned by any ancient writer. Even his name is uncertain, but it was probably Marcus Manilius; in the earlier books the author is...

 described it as "sea-blue", as did the 4th century Avienus
Avienus
Avienus was a Latin writer of the 4th century AD. According to an inscription from Bulla Regia, his full name was Postumius Rufius Festus Avienius.He was a native of Volsinii in Etruria, from the distinguished family of the Rufii Festi...

. It is the standard star for the color white in ancient China, and multiple records from the 2nd century BC up to the 7th century AD all describe Sirius as white in hue.

In 1985, German astronomers Wolfhard Schlosser and Werner Bergmann published an account of an 8th century Lombardic
Lombardy
Lombardy is one of the 20 regions of Italy. The capital is Milan. One-sixth of Italy's population lives in Lombardy and about one fifth of Italy's GDP is produced in this region, making it the most populous and richest region in the country and one of the richest in the whole of Europe...

 manuscript, which contains De cursu stellarum ratio by St. Gregory of Tours
Gregory of Tours
Saint Gregory of Tours was a Gallo-Roman historian and Bishop of Tours, which made him a leading prelate of Gaul. He was born Georgius Florentius, later adding the name Gregorius in honour of his maternal great-grandfather...

. The Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 text taught readers how to determine the times of nighttime prayers from positions of the stars, and Sirius is described within as rubeola — "reddish". The authors proposed this was further evidence Sirius B had been a red giant at the time. However, other scholars replied that it was likely St. Gregory had been referring to Arcturus instead.

The possibility that stellar evolution
Stellar evolution
Stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. Depending on the mass of the star, this lifetime ranges from only a few million years to trillions of years .Stellar evolution is not studied by observing the life of a single...

 of either Sirius A or Sirius B could be responsible for this discrepancy has been rejected by astronomers on the grounds that the timescale of thousands of years is too short and that there is no sign of the nebulosity in the system that would be expected had such a change taken place. An interaction with a third star, to date undiscovered, has also been proposed as a possibility for a red appearance. Alternative explanations are either that the description as red is a poetic metaphor for ill fortune, or that the dramatic scintillation
Scintillation (astronomy)
Scintillation or twinkling are generic terms for rapid variations in apparent brightness or color of a distant luminous object viewed through a medium, most commonly the atmosphere ....

s of the star when it was observed rising left the viewer with the impression that it was red. To the naked eye, it often appears to be flashing with red, white and blue hues when near the horizon.

Visibility



With an apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 of −1.46, Sirius is the brightest star in the night sky, almost twice the brightness of the second brightest star, Canopus
Canopus
Canopus |Alpha]] Carinae) is the brightest star in the southern constellation of Carina and Argo Navis, and the second brightest star in the night-time sky, after Sirius. Canopus's visual magnitude is −0.72, and it has an absolute magnitude of −5.53.Canopus is a supergiant of spectral...

. However, it is not as bright as the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

, Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

, or Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

. At times, Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...

 and Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

 are also brighter than Sirius. Sirius can be seen from almost every inhabited region of the Earth's surface, with only those north of 73 degrees
Northernmost settlements
Some of the northernmost settlements in the world are:-Larger cities north of the Arctic circle:-See also:*Southernmost settlements*Extreme points of Earth*The world's most northern bagpipe orchestra, city, capital, zoo etc....

 unable to see it. However, it does not rise very high when viewed from some northern cities, reaching only 13° above the horizon from Saint Petersburg
Saint Petersburg
Saint Petersburg is a city and a federal subject of Russia located on the Neva River at the head of the Gulf of Finland on the Baltic Sea...

. Sirius, along with Procyon
Procyon
Procyon is the brightest star in the constellation Canis Minor. To the naked eye, it appears to be a single star, the seventh brightest in the night sky with a visual apparent magnitude of 0.34...

 and Betelgeuse, forms one of the three vertices
Vertex (geometry)
In geometry, a vertex is a special kind of point that describes the corners or intersections of geometric shapes.-Of an angle:...

 of the Winter Triangle to observers in the Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

. Due to its declination
Declination
In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...

 of roughly −17°, Sirius is a circumpolar star
Circumpolar star
A circumpolar star is a star that, as viewed from a given latitude on Earth, never sets , due to its proximity to one of the celestial poles...

 from latitudes south of 73° S. From the Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...

 in early July, Sirius can be seen in both the evening where it sets after the Sun, and in the morning where it rises before the Sun.

Sirius can even be observed in daylight with the naked eye under the right conditions. Ideally, the sky should be very clear, with the observer at a high altitude, the star passing overhead, and the Sun low down on the horizon. These observing conditions are more easily met in the southern hemisphere, due to the southerly declination of Sirius.

The orbital motion of the Sirius binary system brings the two stars to a minimum angular separation of 3 arcseconds and a maximum of 11 arcseconds. At the closest approach, it is an observational challenge to distinguish the white dwarf from its more luminous companion, requiring a telescope with at least 300 mm (12 in) aperture and excellent seeing conditions. A periastron occurred in 1994 and the pair have since been moving apart, making them easier to separate with a telescope.

At a distance of 2.6 parsecs (8.6 ly), the Sirius system contains two of the eight nearest stars to the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

 and is the fifth closest stellar system to ours. This proximity is the main reason for its brightness, as with other near stars such as Alpha Centauri
Alpha Centauri
Alpha Centauri is the brightest star in the southern constellation of Centaurus...

 and in stark contrast to distant, highly luminous supergiants such as Canopus, Rigel or Betelgeuse. However, it is still around 25 times more luminous than the Sun. The closest large neighbouring star to Sirius is Procyon, 1.61 parsecs (5.24 ly) away. The Voyager 2
Voyager 2
The Voyager 2 spacecraft is a 722-kilogram space probe launched by NASA on August 20, 1977 to study the outer Solar System and eventually interstellar space...

spacecraft, launched in 1977 to study the four Jovian planets in the Solar System, is expected to pass within 4.3 ly of Sirius in approximately 296,000 years.

System



Sirius is a binary star system consisting of two white stars orbiting each other with a separation of about 20 AU (roughly the distance between the Sun and Uranus
Uranus
Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus , the father of Cronus and grandfather of Zeus...

) and a period of 50.1 years. The brighter component, termed Sirius A, is a main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...

 star of spectral type A1V, with an estimated surface temperature of 9,940 K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...

. Its companion, Sirius B, is a star that has already evolved off the main sequence and become a white dwarf. Currently 10,000 times less luminous in the visual spectrum, Sirius B was once the more massive of the two. The age of the system has been estimated at around 230 million years. Early in its lifespan it was thought to have been two bluish white stars orbiting each other in an elliptical orbit every 9.1 years. The system emits a higher than expected level of infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

 radiation, as measured by IRAS
IRAS
The Infrared Astronomical Satellite was the first-ever space-based observatory to perform a survey of the entire sky at infrared wavelengths....

 space-based observatory. This may be an indication of dust in the system, and is considered somewhat unusual for a binary star. The Chandra X-ray Observatory
Chandra X-ray Observatory
The Chandra X-ray Observatory is a satellite launched on STS-93 by NASA on July 23, 1999. It was named in honor of Indian-American physicist Subrahmanyan Chandrasekhar who is known for determining the maximum mass for white dwarfs. "Chandra" also means "moon" or "luminous" in Sanskrit.Chandra...

 image shows Sirius B outshining its bright partner as it is a brighter X-ray source.

Sirius A



Sirius A has a mass double that of the Sun. The radius of this star has been measured by an astronomical interferometer
Astronomical interferometer
An astronomical interferometer is an array of telescopes or mirror segments acting together to probe structures with higher resolution by means of interferometry....

, giving an estimated angular diameter of 5.936±0.016 mas. The projected rotational velocity
Stellar rotation
Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface....

 is a relatively low 16 km/s, which does not produce any significant flattening of its disk. This is at marked variance with the similar-sized Vega
Vega
Vega is the brightest star in the constellation Lyra, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere, after Arcturus...

, which rotates at a much faster 274 km/s and bulges prominently around its equator. A weak magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...

 has been detected on the surface of Sirius A.

Stellar models suggest that the star formed during the collapsing of a molecular cloud
Molecular cloud
A molecular cloud, sometimes called a stellar nursery if star formation is occurring within, is a type of interstellar cloud whose density and size permits the formation of molecules, most commonly molecular hydrogen ....

, and that after years, its internal energy generation was derived entirely from nuclear reactions. The core became convective
Convection zone
The convection zone of a star is the range of radii in which energy is transported primarily by convection. In the radiation zone, energy is transported by radiation...

 and utilized the CNO cycle
CNO cycle
The CNO cycle is one of two sets of fusion reactions by which stars convert hydrogen to helium, the other being the proton–proton chain. Unlike the proton–proton chain reaction, the CNO cycle is a catalytic cycle. Theoretical models show that the CNO cycle is the dominant source of energy in stars...

 for energy generation. It is predicted that Sirius A will have completely exhausted the store of hydrogen at its core within a billion (109) years of its formation. At this point it will pass through a red giant
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...

 stage, then settle down to become a white dwarf.

Sirius A is classed as an Am star
Am star
An Am star or metallic-line star is a type of chemically peculiar star of spectral type A whose spectrum has strong and often variable absorption lines of metals such as zinc, strontium, zirconium, and barium, and deficiencies of others, such as calcium and scandium...

 because the spectrum shows deep metallic absorption lines, indicating an enhancement in elements heavier than helium, such as iron. When compared to the Sun, the proportion of iron in the atmosphere of Sirius A relative to hydrogen is given by , which is equivalent to 100.5, meaning it has 316% of the proportion of iron in the Sun's atmosphere. The high surface content of metallic elements is unlikely to be true of the entire star. Instead these may be suspended by a thin convection zone
Convection zone
The convection zone of a star is the range of radii in which energy is transported primarily by convection. In the radiation zone, energy is transported by radiation...

 at the surface.

Sirius B



With a mass nearly equal to the Sun's, Sirius B is one of the more massive white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...

s known (0.98 solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...

); it is almost double the 0.5–0.6 solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...

 average. Yet that same mass is packed into a volume roughly equal to the Earth. The current surface temperature is 25,200 K. However, since there is no internal source of energy generation, Sirius B will steadily cool as the remaining heat is radiated into space over a period of more than two billion years.

A white dwarf forms only after the star has evolved from the main sequence and then passed through a red giant stage. This occurred when Sirius B was less than half its current age, around 120 million years ago. The original star had an estimated 5 solar masses and was a B-type star (roughly B4-5) when it still was on the main sequence. While it passed through the red giant stage, Sirius B may have enriched the metallicity
Metallicity
In astronomy and physical cosmology, the metallicity of an object is the proportion of its matter made up of chemical elements other than hydrogen and helium...

 of its companion.

This star is primarily composed of a carbon-oxygen mixture that was generated by helium fusion in the progenitor star. This is overlaid by an envelope of lighter elements, with the materials segregated by mass because of the high surface gravity. Hence the outer atmosphere of Sirius B is now almost pure hydrogen—the element with the lowest mass—and no other elements are seen in this star's spectrum.

Sirius star cluster


In 1909, Ejnar Hertzsprung
Ejnar Hertzsprung
Ejnar Hertzsprung was a Danish chemist and astronomer.Hertzsprung was born in Copenhagen. In the period 1911–1913, together with Henry Norris Russell, he developed the Hertzsprung–Russell diagram....

 was the first to suggest that Sirius was a member of the Ursa Major Moving Group
Ursa Major Moving Group
The Ursa Major Moving Group, also known as Collinder 285 or Ursa Major association, is a nearby stellar moving group, a set of stars with common velocities in space and thought to have a common origin. Its core is located roughly 80 light years away...

, based on his observations of the system's movements across the sky. The Ursa Major Group is a set of 220 stars that share a common motion through space and were once formed as members of an open cluster
Open cluster
An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...

, which has since become gravitationally unbound. However, analyses in 2003 and 2005 found Sirius's membership in the group to be questionable: the Ursa Major Group has an estimated age of 500±100 million years, while Sirius, with metallicity similar to the Sun's, has an age that is only half this, making it too young to belong to the group. Sirius may instead be a member of the proposed Sirius Supercluster, along with other scattered stars such as Beta Aurigae
Beta Aurigae
Beta Aurigae , traditionally named Menkalinan, is a white subgiant ternary star system approximately 85 light-years away in the constellation Auriga.- Nomenclature :...

, Alpha Coronae Borealis, Beta Crateris
Beta Crateris
Beta Crateris is a star in the constellation Crater. Beta Crateris is a white sub-giant belonging to the spectral class A2, has apparent magnitude 4.48, and is about 265 light years from Earth.-Name:...

, Beta Eridani
Beta Eridani
Beta Eridani is the second brightest star in the constellation of Eridanus, located in the northeast end of this constellation. It has the traditional names Cursa....

 and Beta Serpentis
Beta Serpentis
Beta Serpentis is a star system in the constellation Serpens, in its head . It was a member of indigenous Arabic asterism al-Nasaq al-Sha'āmī, "the Northern Line" of al-Nasaqān "the Two Lines", along with β Her , γ Her and γ Ser .According to the catalogue of stars in the Technical Memorandum...

. This is one of three large clusters located within 500 ly of the Sun. The other two are the Hyades
Hyades (star cluster)
The Hyades is the nearest open cluster to the Solar System and one of the best-studied of all star clusters. The Hipparcos satellite, the Hubble Space Telescope, and infrared color-magnitude diagram fitting have been used to establish a distance to the cluster's center of ~153 ly...

 and the Pleiades
Pleiades (star cluster)
In astronomy, the Pleiades, or Seven Sisters , is an open star cluster containing middle-aged hot B-type stars located in the constellation of Taurus. It is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky...

, and each of these clusters consists of hundreds of stars.

Etymology and cultural significance



The most commonly used proper name of this star comes from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 Sīrius, from the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 Σείριος (Seirios, "glowing" or "scorcher"), although the Greek word itself may have been imported from elsewhere before the Archaic period
Archaic period in Greece
The Archaic period in Greece was a period of ancient Greek history that followed the Greek Dark Ages. This period saw the rise of the polis and the founding of colonies, as well as the first inklings of classical philosophy, theatre in the form of tragedies performed during Dionysia, and written...

, one authority suggesting a link with the Egyptian god Osiris
Osiris
Osiris is an Egyptian god, usually identified as the god of the afterlife, the underworld and the dead. He is classically depicted as a green-skinned man with a pharaoh's beard, partially mummy-wrapped at the legs, wearing a distinctive crown with two large ostrich feathers at either side, and...

. The name's earliest recorded use dates from the 7th century BC in Hesiod
Hesiod
Hesiod was a Greek oral poet generally thought by scholars to have been active between 750 and 650 BC, around the same time as Homer. His is the first European poetry in which the poet regards himself as a topic, an individual with a distinctive role to play. Ancient authors credited him and...

's poetic work Works and Days
Works and Days
Works and Days is a didactic poem of some 800 verses written by the ancient Greek poet Hesiod around 700 BC. At its center, the Works and Days is a farmer's almanac in which Hesiod instructs his brother Perses in the agricultural arts...

. Sirius has over 50 other designations and names attached to it. In Arabic
Arabic language
Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...

 it is known as الشِّعْرَى (transliteration: aš-ši‘rā or ash-shira; the leader), from which the alternate name Aschere derives. In Sanskrit
Sanskrit
Sanskrit , is a historical Indo-Aryan language and the primary liturgical language of Hinduism, Jainism and Buddhism.Buddhism: besides Pali, see Buddhist Hybrid Sanskrit Today, it is listed as one of the 22 scheduled languages of India and is an official language of the state of Uttarakhand...

 it is known as Mrgavyadha "deer hunter", or Lubdhaka "hunter". As Mrgavyadha, the star represents Rudra
Rudra
' is a Rigvedic God, associated with wind or storm, and the hunt. The name has been translated as "The Roarer", or "The Howler"....

 (Shiva
Shiva
Shiva is a major Hindu deity, and is the destroyer god or transformer among the Trimurti, the Hindu Trinity of the primary aspects of the divine. God Shiva is a yogi who has notice of everything that happens in the world and is the main aspect of life. Yet one with great power lives a life of a...

). In Scandinavia, the star has been known as Lokabrenna ("burning done by Loki", or "Loki's torch"). In the astrology
Astrology
Astrology consists of a number of belief systems which hold that there is a relationship between astronomical phenomena and events in the human world...

 of the Middle Ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

, Sirius was a Behenian fixed star
Behenian fixed star
The Behenian fixed stars are a selection of fifteen stars considered especially useful for magical applications in the medieval astrology of Europe and the Arab world. Their name derives from Arabic bahman, "root," as each was considered a source of astrological power for one or more planets...

, associated with beryl
Beryl
The mineral beryl is a beryllium aluminium cyclosilicate with the chemical formula Be3Al26. The hexagonal crystals of beryl may be very small or range to several meters in size. Terminated crystals are relatively rare...

 and juniper
Juniper
Junipers are coniferous plants in the genus Juniperus of the cypress family Cupressaceae. Depending on taxonomic viewpoint, there are between 50-67 species of juniper, widely distributed throughout the northern hemisphere, from the Arctic, south to tropical Africa in the Old World, and to the...

. Its astrological symbol was listed by Heinrich Cornelius Agrippa
Heinrich Cornelius Agrippa
Heinrich Cornelius Agrippa von Nettesheim was a German magician, occult writer, theologian, astrologer, and alchemist.-Life:Agrippa was born in Cologne in 1486...

.

Many cultures have historically attached special significance to Sirius, particularly in relation to dogs. Indeed, it is often colloquially called the "Dog Star" as the brightest star of Canis Major
Canis Major
Canis Major is one of the 88 modern constellations, and was included in the 2nd-century astronomer Ptolemy's 48 constellations. Its name is Latin for 'greater dog', and is commonly represented as one of the dogs following Orion the hunter...

, the "Great Dog" constellation.

This name may derive from the Egyptian god Anubis. The Giza Sphinx, which Robert Temple in his book "The Sphinx Mystery" has documented is actually a dog and not a lion, had originally the head of Anubis. Anubis was a dog and not a jackal as there were no jackals in Egypt at that time. The Sphinx is facing Sirius at the time when the star rises over the horizon at sunrise at the summer solstice, the time when the Nile started flooding, and the Egyptians probably held great ceremonies when that happened.

It was classically depicted as Orion
Orion (mythology)
Orion was a giant huntsman in Greek mythology whom Zeus placed among the stars as the constellation of Orion....

's dog. The Ancient Greeks thought that Sirius's emanations could affect dogs adversely, making them behave abnormally during the "dog days," the hottest days of the summer. The Romans knew these days as dies caniculares, and the star Sirius was called Canicula, "little dog." The excessive panting of dogs in hot weather was thought to place them at risk of desiccation and disease. In extreme cases, a foaming dog might have rabies
Rabies
Rabies is a viral disease that causes acute encephalitis in warm-blooded animals. It is zoonotic , most commonly by a bite from an infected animal. For a human, rabies is almost invariably fatal if post-exposure prophylaxis is not administered prior to the onset of severe symptoms...

, which could infect and kill humans whom they had bitten. Homer
Homer
In the Western classical tradition Homer , is the author of the Iliad and the Odyssey, and is revered as the greatest ancient Greek epic poet. These epics lie at the beginning of the Western canon of literature, and have had an enormous influence on the history of literature.When he lived is...

, in the Iliad
Iliad
The Iliad is an epic poem in dactylic hexameters, traditionally attributed to Homer. Set during the Trojan War, the ten-year siege of the city of Troy by a coalition of Greek states, it tells of the battles and events during the weeks of a quarrel between King Agamemnon and the warrior Achilles...

, describes the approach of Achilles
Achilles
In Greek mythology, Achilles was a Greek hero of the Trojan War, the central character and the greatest warrior of Homer's Iliad.Plato named Achilles the handsomest of the heroes assembled against Troy....

 toward Troy
Troy
Troy was a city, both factual and legendary, located in northwest Anatolia in what is now Turkey, southeast of the Dardanelles and beside Mount Ida...

 in these words:
In Chinese astronomy
Chinese astronomy
Astronomy in China has a very long history, with historians considering that "they [the Chinese] were the most persistent and accurate observers of celestial phenomena anywhere in the world before the Arabs."...

 the star is known as the star of the "celestial wolf" ' onMouseout='HidePop("95447")' href="http://www.absoluteastronomy.com/topics/Pinyin">Chinese romanization
Pinyin
Pinyin is the official system to transcribe Chinese characters into the Roman alphabet in China, Malaysia, Singapore and Taiwan. It is also often used to teach Mandarin Chinese and spell Chinese names in foreign publications and used as an input method to enter Chinese characters into...

: Tiānláng; Japanese romanization
Romanization of Japanese
The romanization of Japanese is the application of the Latin alphabet to write the Japanese language. This method of writing is known as , less strictly romaji, literally "Roman letters", sometimes incorrectly transliterated as romanji or rōmanji. There are several different romanization systems...

: Tenrō; in the Mansion of Jǐng
Well (Chinese constellation)
The Well mansion is one of the Twenty-eight mansions of the Chinese constellations. It is one of the southern mansions of the Vermilion Bird.-Asterisms:...

 (井宿). Farther afield, many nations among the indigenous peoples of North America also associated Sirius with canines; the Seri and Tohono O'odham
Tohono O'odham
The Tohono O'odham are a group of Native American people who reside primarily in the Sonoran Desert of the southeastern Arizona and northwest Mexico...

 of the southwest note the star as a dog that follows mountain sheep, while the Blackfoot
Blackfoot
The Blackfoot Confederacy or Niitsítapi is the collective name of three First Nations in Alberta and one Native American tribe in Montana....

 called it "Dog-face". The Cherokee
Cherokee
The Cherokee are a Native American people historically settled in the Southeastern United States . Linguistically, they are part of the Iroquoian language family...

 paired Sirius with Antares as a dog-star guardian of either end of the "Path of Souls". The Pawnee of Nebraska had several associations; the Wolf (Skidi) tribe knew it as the "Wolf Star", while other branches knew it as the "Coyote Star". Further north, the Alaskan Inuit
Inuit
The Inuit are a group of culturally similar indigenous peoples inhabiting the Arctic regions of Canada , Denmark , Russia and the United States . Inuit means “the people” in the Inuktitut language...

 of the Bering Strait
Bering Strait
The Bering Strait , known to natives as Imakpik, is a sea strait between Cape Dezhnev, Chukotka Autonomous Okrug, Russia, the easternmost point of the Asian continent and Cape Prince of Wales, Alaska, USA, the westernmost point of the North American continent, with latitude of about 65°40'N,...

 called it "Moon Dog".

Several cultures also associated the star with a bow and arrows. The Ancient Chinese visualized a large bow and arrow across the southern sky, formed by the constellations of Puppis
Puppis
Puppis is a constellation in the southern sky. Its name is the Latin word for the poop deck of a ship, and Puppis represents the deck of the ship and its deckhouses...

 and Canis Major. In this, the arrow tip is pointed at the wolf Sirius. A similar association is depicted at the Temple of Hathor
Dendera Temple complex
Dendera Temple complex, . located about 2.5 km south-east of Dendera, Egypt. It is one of the best-preserved temple complexes in Egypt...

 in Dendera
Dendera
Dendera is a small town in Egypt situated on the west bank of the Nile, about 5 km south of Qena, on the opposite side of the river.-History:...

, where the goddess Satet
Satis
In Egyptian mythology, Satis was the deification of the floods of the Nile River, and her cult originated in the ancient city of Swenet, now called Aswan on the southern edge of Egypt. Her name means she who shoots forth referring to the annual flooding of the river...

 has drawn her arrow at Hathor
Hathor
Hathor , is an Ancient Egyptian goddess who personified the principles of love, beauty, music, motherhood and joy. She was one of the most important and popular deities throughout the history of Ancient Egypt...

 (Sirius). Known as "Tir", the star was portrayed as the arrow itself in later Persian culture.

Sirius is mentioned in Surah 53, An-Najm ("The Star"), of the Qur'an
Qur'an
The Quran , also transliterated Qur'an, Koran, Alcoran, Qur’ān, Coran, Kuran, and al-Qur’ān, is the central religious text of Islam, which Muslims consider the verbatim word of God . It is regarded widely as the finest piece of literature in the Arabic language...

, where it is given the name الشِّعْرَى (al-shiʿraa.) The verse is: "وأنَّهُ هُوَ رَبُّ الشِّعْرَى", "That He is the Lord of Sirius (the Mighty Star)." (53:49)

In Theosophy
Theosophy
Theosophy, in its modern presentation, is a spiritual philosophy developed since the late 19th century. Its major themes were originally described mainly by Helena Blavatsky , co-founder of the Theosophical Society...

, it is believed the Seven Stars of the Pleiades
Pleiades in folklore and literature
The high visibility of the star cluster Pleiades in the night sky has guaranteed it a special place in many cultures, both ancient and modern.The astrological Pleiades was originally described in Three Books of Occult Philosophy by Heinrich Cornelius Agrippa .The heliacal rising of Pleiades often...

transmit the spiritual energy of the Seven Rays from the Galactic Logos to the Seven Stars of the Great Bear
Ursa Major
Ursa Major , also known as the Great Bear, is a constellation visible throughout the year in most of the northern hemisphere. It can best be seen in April...

, then to Sirius. From there is it sent via the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 to the god of Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 (Sanat Kumara
Sanat Kumara
According to the post-1900 publications of Theosophy, i.e. the writings of C. W. Leadbeater, Alice A. Bailey, and Benjamin Creme, as well as the Ascended Master Teachings of Guy Ballard, Elizabeth Clare Prophet, Geraldine Innocente, Joshua David Stone, and other Ascended Master Teachings teachers,...

), and finally through the seven Masters of the Seven Rays
Masters of the Ancient Wisdom
The Masters of the Ancient Wisdom are reputed to be enlightened beings originally identified by the Theosophists Helena Blavatsky, Henry S. Olcott, Alfred P. Sinnett, and others. These Theosophists claimed to have met some of the so-called Masters during their lifetimes in different parts of the...

 to the human race
Human Race
Human Race refers to the Human species.Human race may also refer to:*The Human Race, 79th episode of YuYu Hakusho* Human Race Theatre Company of Dayton Ohio* Human Race Machine, a computer graphics device...

.

Dogon


The Dogon people
Dogon people
The Dogon are an ethnic group living in the central plateau region of Mali, south of the Niger bend near the city of Bandiagara in the Mopti region. The population numbers between 400,000 and 800,000 The Dogon are best known for their religious traditions, their mask dances, wooden sculpture and...

 are an ethnic group in Mali
Mali
Mali , officially the Republic of Mali , is a landlocked country in Western Africa. Mali borders Algeria on the north, Niger on the east, Burkina Faso and the Côte d'Ivoire on the south, Guinea on the south-west, and Senegal and Mauritania on the west. Its size is just over 1,240,000 km² with...

, West Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...

, reported to have traditional astronomical knowledge about Sirius that would normally be considered impossible without the use of telescopes. According to Marcel Griaule
Marcel Griaule
Marcel Griaule was a French anthropologist known for his studies of the Dogon people of West Africa, and for pioneering ethnographic field studies in France....

's books Conversations with Ogotemmêli and The Pale Fox they knew about the fifty-year orbital period of Sirius and its companion prior to western astronomers. They also refer to a third star accompanying Sirius A and B. Robert Temple
Robert K. G. Temple
Robert K. G. Temple is an American author best known for his controversial book, The Sirius Mystery which presents the idea that the Dogon people preserve the tradition of contact with intelligent extraterrestrial beings from the Sirius star-system...

's 1976 book The Sirius Mystery
The Sirius Mystery
The Sirius Mystery is a book by Robert K. G. Temple first published by St. Martin's Press in 1975. It presents the hypothesis that the Dogon people of Mali in west Africa, preserve a tradition of contact with intelligent extraterrestrial beings from the Sirius star-system.These beings, who are...

, credits them with knowledge of the four Galilean moons of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

 and the rings of Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...

. This has been the subject of controversy and speculation. According to a 1978 Skeptical Inquirer
Skeptical Inquirer
The Skeptical Inquirer is a bimonthly American magazine published by the Committee for Skeptical Inquiry with the subtitle: The magazine for science and reason....

article it is possibly the result of cultural contamination. Some have suggested the contaminators to have been the ethnographers themselves. Others see this explanation as being too simplistic.

Modern legacy


Sirius is frequently a subject used in science fiction
Science fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...

 and related popular culture
Popular culture
Popular culture is the totality of ideas, perspectives, attitudes, memes, images and other phenomena that are deemed preferred per an informal consensus within the mainstream of a given culture, especially Western culture of the early to mid 20th century and the emerging global mainstream of the...

, and even the subject of poetry. Sirius is featured on the coat of arms of Macquarie University
Macquarie University
Macquarie University is an Australian public teaching and research university located in Sydney, with its main campus situated in Macquarie Park. Founded in 1964 by the New South Wales Government, it was the third university to be established in the metropolitan area of Sydney...

, and is the name of its alumnae journal. The name of the North American satellite radio
Satellite radio
Satellite radio is an analogue or digital radio signal that is relayed through one or more satellites and thus can be received in a much wider geographical area than terrestrial FM radio stations...

 company, Satellite CD Radio, Inc., was changed to Sirius Satellite Radio
Sirius Satellite Radio
Sirius Satellite Radio is a satellite radio service operating in North America, owned by Sirius XM Radio.Headquartered in New York City, with smaller studios in Los Angeles and Memphis, Sirius was officially launched on July 1, 2002 and currently provides 69 streams of music and 65 streams of...

 in November 1999, being named after "the brightest star in the night sky". Composer Karlheinz Stockhausen
Karlheinz Stockhausen
Karlheinz Stockhausen was a German composer, widely acknowledged by critics as one of the most important but also controversial composers of the 20th and early 21st centuries. Another critic calls him "one of the great visionaries of 20th-century music"...

 has been claimed to have said on several occasions that he came from a planet in the Sirius system. Astronomer Noah Brosch has speculated that the name of the character Sirius Black
Sirius Black
Sirius Black is a fictional character in J. K. Rowling's Harry Potter series. Sirius was first mentioned briefly in Harry Potter and the Sorcerer's Stone as a wizard who lent Rubeus Hagrid a flying motorbike shortly after Lord Voldemort killed James and Lily Potter...

 from the Harry Potter
Harry Potter
Harry Potter is a series of seven fantasy novels written by the British author J. K. Rowling. The books chronicle the adventures of the adolescent wizard Harry Potter and his best friends Ron Weasley and Hermione Granger, all of whom are students at Hogwarts School of Witchcraft and Wizardry...

 stories might have been inspired by "Sirius B", and notes that the wizard has the ability to transform into a dog.
In the BBC Doctor Who series, the Doctor reveals the star actually consists of two smaller ones.
Sirius is one of the 27 stars on the flag of Brazil
Flag of Brazil
The national flag of Brazil is a blue disc depicting a starry sky spanned by a curved band inscribed with the national motto, within a yellow rhombus, on a green field. Brazil officially adopted this design for its national flag on November 19, 1889, replacing the flag of the second Empire of Brazil...

, where it represents the state of Mato Grosso
Mato Grosso
Mato Grosso is one of the states of Brazil, the third largest in area, located in the western part of the country.Neighboring states are Rondônia, Amazonas, Pará, Tocantins, Goiás and Mato Grosso do Sul. It also borders Bolivia to the southwest...

.

Seven ships of Great Britain's Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

 have been called since the 18th century, with the first
HMS Sirius (1786)
HMS Sirius was the flagship of the First Fleet, which set out from Portsmouth, England, in 1787 to establish the first European colony in New South Wales, Australia. Sirius was wrecked off the coast of Norfolk Island in the Pacific Ocean in 1790....

 being the flagship
Flagship
A flagship is a vessel used by the commanding officer of a group of naval ships, reflecting the custom of its commander, characteristically a flag officer, flying a distinguishing flag...

 of the First Fleet
First Fleet
The First Fleet is the name given to the eleven ships which sailed from Great Britain on 13 May 1787 with about 1,487 people, including 778 convicts , to establish the first European colony in Australia, in the region which Captain Cook had named New South Wales. The fleet was led by Captain ...

 to Australia in 1788. The Royal Australian Navy
Royal Australian Navy
The Royal Australian Navy is the naval branch of the Australian Defence Force. Following the Federation of Australia in 1901, the ships and resources of the separate colonial navies were integrated into a national force: the Commonwealth Naval Forces...

 subsequently named a vessel in honor of the flagship. American vessels include the as well as a monoplane model—the Lockheed Sirius
Lockheed Sirius
The Lockheed Model 8 Sirius was single engine, propeller-driven monoplane designed and built by Jack Northrop and Gerard Vultee while they were engineers at Lockheed in 1929, at the request of Charles Lindbergh...

, the first of which was flown by Charles Lindbergh
Charles Lindbergh
Charles Augustus Lindbergh was an American aviator, author, inventor, explorer, and social activist.Lindbergh, a 25-year-old U.S...

. The name was also adopted by Mitsubishi Motors
Mitsubishi Motors
is a multinational automaker headquartered in Minato, Tokyo. In 2009 it was the fifth-largest Japan-based automaker and the 17th-largest in the world measured by production...

 as the Mitsubishi Sirius engine
Mitsubishi Sirius engine
The Mitsubishi Sirius or 4G6/4D6 engine is the name of one of Mitsubishi Motors' four series of inline 4 automobile engines, along with Astron, Orion, and Saturn. The 4G6 are gasoline engines, the 4D6 diesels.-4G61:...

 in 1980.

See also



External links