Sirius

Sirius BSirius superclusterDog StarSirius ASothisDog-starSirianα Canis MajorisSirius starStar of Sirius
Sirius (, designated α Canis Majoris (Latinized to Alpha Canis Majoris, abbreviated Alpha CMa, α CMa)) is the brightest star in the night sky.wikipedia
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Apparent magnitude

apparent visual magnitudemagnitudevisual magnitude
With a visual apparent magnitude of −1.46, Sirius is almost twice as bright as Canopus, the next brightest star.
The brightest astronomical objects have negative apparent magnitudes: for example, Venus at −4.2 or Sirius at −1.46.

White dwarf

white dwarfswhite dwarf starcentral star
Sirius is a binary star consisting of a main-sequence star of spectral type A0 or A1, termed Sirius A, and a faint white dwarf companion of spectral type DA2, termed 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.

Canopus

Alpha Carinaeα Carinaea first magnitude star
With a visual apparent magnitude of −1.46, Sirius is almost twice as bright as Canopus, the next brightest star.
It is the second-brightest star in the night sky, after Sirius.

Binary star

spectroscopic binaryeclipsing binarybinary
Sirius is a binary star consisting of a main-sequence star of spectral type A0 or A1, termed Sirius A, and a faint white dwarf companion of spectral type DA2, termed Sirius B. The distance between the two varies between 8.2 and 31.5 astronomical units as they orbit every 50 years.
Examples of binaries are Sirius, and Cygnus X-1 (Cygnus X-1 being a well-known black hole).

Dog days

dog-daysDog Days of Summerdog-day
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, mostly 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.

Canis Major

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

List of brightest stars

brightest starsbrightest starone of the brightest stars
Sirius (, designated α Canis Majoris (Latinized to Alpha Canis Majoris, abbreviated Alpha CMa, α CMa)) is the brightest star in the night sky.

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, mostly 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.

Sopdet

SothisSpdt
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.

Sothic cycle

SothicSothic yearHeliacal Rise
The Egyptians continued to note the times of Sirius' 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.

Egyptian calendar

EgyptianEgyptian civil calendarancient Egyptian calendar
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.

Star

starsstellarmassive star
Sirius is a binary star consisting of a main-sequence star of spectral type A0 or A1, termed Sirius A, and a faint white dwarf companion of spectral type DA2, termed Sirius B. The distance between the two varies between 8.2 and 31.5 astronomical units as they orbit every 50 years.
By comparing the spectra of stars such as Sirius to the Sun, they found differences in the strength and number of their absorption lines—the dark lines in stellar spectra caused by the atmosphere's absorption of specific frequencies.

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).

Rigel

Beta Orionisβ Ori (Rigel)β Orionis
It is 25 times more luminous than the Sun but has a significantly lower luminosity than other bright stars such as Canopus or Rigel.
The star is a vertex of the "Winter Hexagon", an asterism that includes Aldebaran, Capella, Pollux, Procyon, and Sirius.

Procyon

Procyon BProcyon ACanis minor
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.
It forms one of the three vertices of the Winter Triangle asterism, in combination with Sirius and Betelgeuse.

Arcturus

ArcturiansArcturianAlpha Boo
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).

List of nearest stars and brown dwarfs

List of nearest starspassing starsnearest stars
At a distance of 2.64 pc, the Sirius system is one of Earth's nearest neighbours.

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.

Flooding of the Nile

Nile floodannual floodingNile floods
This rising occurs at Cairo on 19July (Julian), placing it just prior to 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.

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.
Following the three stars of Orion's belt in the opposite direction to Sirius, the first bright star encountered is Aldebaran.

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.

Kea (island)

KeaCeosKeos
The inhabitants of the island of Ceos in the Aegean Sea would offer sacrifices to Sirius and Zeus to bring cooling breezes and would await the reappearance of the star in summer.
The inhabitants were known for offering sacrifices to the Dog Star, Sirius and to Zeus to bring cooling breezes while awaiting the reappearance of Sirius in summer; if the star rose clear, it would portend good fortune; if it was misty or faint, then it foretold (or emanated) pestilence.

Walter Sydney Adams

Walter S. AdamsW. S. AdamsWalter Adams
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.

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.

Sun

solarSolThe Sun
Due to its declination of roughly −17°, Sirius is a circumpolar star from latitudes south of 73° S. From the Southern Hemisphere 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.
This is about 13 billion times brighter than the next brightest star, Sirius, which has an apparent magnitude of −1.46.