Sirius

SothisDog StarSirius BDog-starSirianSirioα Canis Majorisbrightest star in the nightCanis maiorCelestial Wolf
Sirius (, a latinisation of Greek Σείριος, Seirios, lit."glowing" or "scorching") is a binary star and the brightest star in the night sky.wikipedia
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Canopus

α Carinaea first magnitude starCanopean
With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. This proximity is the main reason for its brightness, as with other near stars such as α Centauri and in contrast to distant, highly luminous supergiants such as Canopus, Rigel or Betelgeuse.
Canopus, also designated α Carinae (Latinised to Alpha Carinae, abbreviated Alpha Car, α Car), is the brightest star in the southern constellation of Carina, and the second-brightest star in the night sky, after Sirius.

Apparent magnitude

apparent visual magnitudemagnitudevisual magnitude
With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star.
The brighter an object appears, the lower its magnitude value (i.e. inverse relation), with the brightest astronomical objects having negative apparent magnitudes: for example Sirius at −1.46.

White dwarf

white dwarfswhite dwarf starcentral star
The binary system consists of a main-sequence star of spectral type A0 or A1, termed Sirius A, and a faint white dwarf companion of spectral type DA2, designated Sirius B. The distance between the two varies between 8.2 and 31.5 astronomical units as they orbit every 50 years.
The nearest known white dwarf is Sirius B, at 8.6 light years, the smaller component of the Sirius binary star.

Canis Major

CMaGreat DogSirius
Sirius is also known colloquially as the "Dog Star", reflecting its prominence in its constellation, Canis Major (Greater Dog).
Canis Major contains Sirius, the brightest star in the night sky, known as the "dog star".

Dog days

dog-daysdog-dayCanicular
The heliacal rising of Sirius marked the flooding of the Nile in Ancient Egypt and the "dog days" of summer for the ancient Greeks, while to the Polynesians in the Southern Hemisphere the star marked winter and was an important reference for their navigation around the Pacific Ocean.
They were historically the period following the heliacal rising of the star system Sirius, which Greek and Roman astrology connected with heat, drought, sudden thunderstorms, lethargy, fever, mad dogs, and bad luck.

Binary star

spectroscopic binaryeclipsing binarybinary
Sirius (, a latinisation of Greek Σείριος, Seirios, lit."glowing" or "scorching") is a binary star and the brightest star in the night sky.
Examples of binaries are Sirius, and Cygnus X-1 (Cygnus X-1 being a well-known black hole).

Star system

multiple star systemmultiple systemstriple star
Examples of binary systems are Sirius, Procyon and Cygnus X-1, the last of which probably consists of a star and a black hole.

Alpha

ααalfa
The system has the Bayer designation α (Alpha) Canis Majoris.

Sopdet

Sothisgoddess of the Sirius starSpdt
Owing to the flood's own irregularity, the extreme precision of the star's return made it important to the ancient Egyptians, who worshipped it as the goddess Sopdet (, "Triangle";, Sō̂this), guarantor of the fertility of their land.
Sopdet is the ancient Egyptian name of the star Sirius and its personification as an Egyptian goddess.

Heliacal rising

heliacal risingsheliacallyacronychal rising
The heliacal rising of Sirius marked the flooding of the Nile in Ancient Egypt and the "dog days" of summer for the ancient Greeks, while to the Polynesians in the Southern Hemisphere the star marked winter and was an important reference for their navigation around the Pacific Ocean.
Historically, the most important such rising is that of Sirius, which was an important feature of the Egyptian calendar and astronomical development.

Sothic cycle

SothicHeliacal RiseHeliacal rise of Sirius
The Egyptians continued to note the times of Sirius's annual return, which may have led them to the discovery of the 1460-year Sothic cycle and influenced the development of the Julian and Alexandrian calendars.
During a Sothic cycle, the 365-day year loses enough time that the start of its year once again coincides with the heliacal rising of the star Sirius ( or Sopdet, "Triangle";, Sō̂this) on 19 July in the Julian calendar.

List of brightest stars

brightest starsbrightest starone of the brightest stars
Sirius (, a latinisation of Greek Σείριος, Seirios, lit."glowing" or "scorching") is a binary star and the brightest star in the night sky.

Egyptian calendar

Egyptianancient Egyptian calendarCalendar
The Egyptian civil calendar was apparently initiated to have its New Year "Mesori" coincide with the appearance of Sirius, although its lack of leap years meant that this congruence only held for four years until its date began to wander backwards through the months.
A tablet from the reign of the First-Dynasty pharaoh Djer was once thought to indicate that the Egyptians had already established a link between the heliacal rising of Sirius ( or Sopdet, "Triangle";, Sôthis) and the beginning of their year, but more recent analysis has questioned whether the tablet's picture refers to Sirius at all.

Procyon

Canis minorProcyon Aα CMi
Sirius served as the body of a "Great Bird" constellation called Manu, with Canopus as the southern wingtip and Procyon the northern wingtip, which divided the Polynesian night sky into two hemispheres. Sirius, along with Procyon and Betelgeuse, forms one of the three vertices of the Winter Triangle to observers in the Northern Hemisphere.
Procyon is usually the eighth-brightest star in the night sky, culminating at midnight on January 14. It forms one of the three vertices of the Winter Triangle asterism, in combination with Sirius and Betelgeuse.

Arcturus

ArcturiansArcturianArcturan
The other five are class M and K stars, such as Arcturus and Betelgeuse. The bright stars Aldebaran, Arcturus and Sirius were noted to have moved significantly; Sirius had progressed about 30 arc minutes (about the diameter of the Moon) to the southwest.
With an apparent visual magnitude of −0.05, Arcturus is the brightest star in the northern celestial hemisphere and the fourth-brightest star in the night sky, after Sirius (−1.46 apparent magnitude), Canopus (−0.72) and α Centauri (combined magnitude of −0.27).

Vega

2828Botercadentconstellation of Vega
This is at marked variance with the similar-sized Vega, which rotates at a much faster 274 km/s and bulges prominently around its equator.
It is relatively close at only 25 light-years from the Sun, and, together with Arcturus and Sirius, one of the most luminous stars in the Sun's neighborhood.

Mesori

Mesrafourth month12th month
The Egyptian civil calendar was apparently initiated to have its New Year "Mesori" coincide with the appearance of Sirius, although its lack of leap years meant that this congruence only held for four years until its date began to wander backwards through the months.
The intercalary month was added every few years as needed to maintain the heliacal rising of Sirius within the month.

Alpha Centauri

α CentauriAlphaα Centauri A
This proximity is the main reason for its brightness, as with other near stars such as α Centauri and in contrast to distant, highly luminous supergiants such as Canopus, Rigel or Betelgeuse.
Alpha Centauri A and B are Sun-like stars (Class G and K), and together they form the binary star Alpha Centauri AB. To the naked eye, the two main components appear to be a single star with an apparent magnitude of −0.27, forming the brightest star in the southern constellation of Centaurus and the third-brightest in the night sky, outshone only by Sirius and Canopus.

Flooding of the Nile

annual floodingfloodingfloodings
This occurs at Cairo on 19July (Julian), placing it just prior to the summer solstice and the onset of the annual flooding of the Nile during antiquity.
This cycle was so consistent that the Egyptians timed its onset using the heliacal rising of Sirius, the key event used to set their calendar.

List of nearest stars and brown dwarfs

passing starsnearest starsclosest stars
At a distance of 2.6 parsecs (8.6 ly), as determined by the Hipparcos astrometry satellite, the Sirius system is one of Earth's near neighbours.

Winter Triangle

Sirius, along with Procyon and Betelgeuse, forms one of the three vertices of the Winter Triangle to observers in the Northern Hemisphere.
It is an imaginary equilateral triangle drawn on the celestial sphere, with its defining vertices at Sirius, Betelgeuse, and Procyon, the primary stars in the three constellations of Canis Major, Orion, and Canis Minor, respectively.

William Huggins

Sir William HugginsHugginsHuggins, Sir William
Sir William Huggins examined the spectrum of the star and observed a red shift.
With observations of Sirius showing a redshift in 1868, Huggins hypothesized that a radial velocity of the star could be computed.

Aldebaran

Alpha Tauribrightest starRohini
The bright stars Aldebaran, Arcturus and Sirius were noted to have moved significantly; Sirius had progressed about 30 arc minutes (about the diameter of the Moon) to the southwest.
This, as well as observations of the changing positions of stars Sirius and Arcturus, led to the discovery of proper motion.

Absolute magnitude

Hbolometric magnitudeabsolute magnitude (H)
Sirius A is about twice as massive as the Sun and has an absolute visual magnitude of +1.42.
For comparison, Sirius has an absolute magnitude of 1.4, which is brighter than the Sun, whose absolute visual magnitude is 4.83 (it actually serves as a reference point).

Walter Sydney Adams

Walter AdamsWalter S. AdamsAdams, Walter Sydney
In 1915, Walter Sydney Adams, using a 60-inch (1.5 m) reflector at Mount Wilson Observatory, observed the spectrum of Sirius B and determined that it was a faint whitish star.
In 1915 he began a study of the companion of Sirius and found that despite a size only slightly larger than the Earth, the surface of the star was brighter per unit area than the Sun and it was about as massive.