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Sirius A / B <tr><td colspan="2" style="text-align:center;">
{{#invoke:Location map|main}}
The position of Sirius (circled).
</tr></td>

Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Canis Major
Sirius ({{#invoke:IPAc-en|main}}<ref name="Dictionary.com" />) system
Right ascension 06h 45m 08.91728s<ref name=aaa474_2_653/>
Declination replace|source=−16|-|−|1}}° 42′ 58.0171″<ref name=aaa474_2_653/>
Apparent magnitude (V) −1.46<ref name="Hoffleit1991" />
Sirius A
Right ascension citation CitationClass=journal

}}</ref>

Declination replace|source=−16|-|−|1}}° 42′ 58.02″<ref name=tychods/>
Apparent magnitude (V) −1.47<ref name=holberg2013/>
Sirius B
Right ascension citation CitationClass=journal

}}</ref>

Declination replace|source=−16|-|−|1}}° 43′ 06″<ref name=gianninas/>
Apparent magnitude (V) citation CitationClass=journal

}}</ref>

  1. REDIRECT

<tr><th style="background-color: #FFFFC0; text-align: center;" colspan="2">Details</th></tr></th></tr><tr><th colspan="2" style="text-align: center">α CMa A</th></tr><tr style="vertical-align:baseline;"><td>Mass</td><td>2.02<ref name="Liebert2005" /> M</td></tr><tr style="vertical-align:baseline;"><td>Radius</td><td>1.711<ref name="Liebert2005" /> R</td></tr><tr style="vertical-align:baseline;"><td>Luminosity</td><td>25.4<ref name="Liebert2005" /> </td></tr><tr style="vertical-align:baseline;"><td>Surface gravity (log g)</td><td>4.33<ref name="Adelman2004" /> cgs</td></tr><tr style="vertical-align:baseline;"><td>Temperature</td><td>9,940<ref name="Adelman2004" /> K</td></tr><tr style="vertical-align:baseline;"><td>Metallicity [Fe/H]</td><td>0.50<ref name="Qiu2001" /> dex</td></tr><tr style="vertical-align:baseline;"><td>Rotation</td><td>16 km/s<ref name="Royer2002" /></td></tr><tr style="vertical-align:baseline;"><td>Age</td><td>225–250<ref name="Liebert2005" /> Myr</td></tr><tr><th colspan="2" style="text-align: center">α CMa B</th></tr><tr style="vertical-align:baseline;"><td>Mass</td><td>0.978<ref name="Liebert2005" /> M</td></tr><tr style="vertical-align:baseline;"><td>Radius</td><td>0.0084 ± 3%<ref name="Holberg1998" /> R</td></tr><tr style="vertical-align:baseline;"><td>Luminosity</td><td>0.056<ref name=sweeney>{{#invoke:Citation/CS1|citation

CitationClass=journal

}}</ref> </td></tr><tr style="vertical-align:baseline;"><td>Surface gravity (log g)</td><td>8.57<ref name="Holberg1998" /> cgs</td></tr><tr style="vertical-align:baseline;"><td>Temperature</td><td>25,200<ref name="Liebert2005" /> K</td></tr> <tr><th style="background-color: #FFFFC0; text-align: center;" colspan="2">Database references</th></tr><tr style="vertical-align: top;"><td>SIMBAD</td><td>The system</tr><tr style="vertical-align: top;"><td></td><td>A</tr><tr style="vertical-align: top;"><td></td><td>B</tr>

Sirius ({{#invoke:IPAc-en|main}}) is the brightest star (in fact, a star system) in the Earth's night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name "Sirius" is derived from the Ancient Greek Σείριος (Seirios), meaning "glowing" or "scorcher". The system has the Bayer designation Alpha Canis Majoris (α CMa). What the naked eye perceives as a single star is actually a binary star system, consisting of a white main-sequence star of spectral type A1V, termed Sirius A, and a faint white dwarf companion of spectral type DA2, called Sirius B. The distance separating Sirius A from its companion varies between 8.2 and 31.5 AU.<ref name="Schaaf2008" />

Sirius appears bright because of both its intrinsic luminosity and its proximity to Earth. At a distance of 2.6 parsecs (8.6 ly), as determined by the Hipparcos astrometry satellite,<ref name="aaa474_2_653" /><ref name=aaa323_L49>{{#invoke:citation/CS1|citation

CitationClass=citation

}}</ref><ref name=GSM>{{#invoke:citation/CS1|citation

CitationClass=citation

}}</ref> the Sirius system is one of Earth's near neighbors. Sirius is gradually moving closer to the Solar System, so it will slightly increase in brightness over the next 60,000 years. After that time its distance will begin to increase, but it will continue to be the brightest star in the Earth's sky for the next 210,000 years.<ref>Sky and Telescope, April 1998 (p60), based on computations from Hipparcos data.</ref>

Sirius A is about twice as massive as the Sun (M) and has an absolute visual magnitude of 1.42. It is 25 times more luminous than the Sun<ref name="Liebert2005" /> but has a significantly lower luminosity than other bright stars such as Canopus or Rigel. The system is between 200 and 300 million years old.<ref name="Liebert2005" /> It was originally composed of two bright bluish stars. The more massive of these, Sirius B, consumed its resources and became a red giant before shedding its outer layers and collapsing into its current state as a white dwarf around 120 million years ago.<ref name="Liebert2005" />

Sirius is also known colloquially as the "Dog Star", reflecting its prominence in its constellation, Canis Major (Greater Dog).<ref name="Allen1899" /> 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.


Sirius sections
Intro   Observational history    Visibility    System    Etymology and cultural significance    See also    Notes    References    External links   

PREVIOUS: IntroNEXT: Observational history
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Sirius::title    First::journal    Holberg::author    Volume::pages    Bibcode::stars    Issue::citation

{{#invoke:redirect hatnote|redirect}}

Sirius A / B <tr><td colspan="2" style="text-align:center;">
{{#invoke:Location map|main}}
The position of Sirius (circled).
</tr></td>

Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Canis Major
Sirius ({{#invoke:IPAc-en|main}}<ref name="Dictionary.com" />) system
Right ascension 06h 45m 08.91728s<ref name=aaa474_2_653/>
Declination replace|source=−16|-|−|1}}° 42′ 58.0171″<ref name=aaa474_2_653/>
Apparent magnitude (V) −1.46<ref name="Hoffleit1991" />
Sirius A
Right ascension citation CitationClass=journal

}}</ref>

Declination replace|source=−16|-|−|1}}° 42′ 58.02″<ref name=tychods/>
Apparent magnitude (V) −1.47<ref name=holberg2013/>
Sirius B
Right ascension citation CitationClass=journal

}}</ref>

Declination replace|source=−16|-|−|1}}° 43′ 06″<ref name=gianninas/>
Apparent magnitude (V) citation CitationClass=journal

}}</ref>

  1. REDIRECT

<tr><th style="background-color: #FFFFC0; text-align: center;" colspan="2">Details</th></tr></th></tr><tr><th colspan="2" style="text-align: center">α CMa A</th></tr><tr style="vertical-align:baseline;"><td>Mass</td><td>2.02<ref name="Liebert2005" /> M</td></tr><tr style="vertical-align:baseline;"><td>Radius</td><td>1.711<ref name="Liebert2005" /> R</td></tr><tr style="vertical-align:baseline;"><td>Luminosity</td><td>25.4<ref name="Liebert2005" /> </td></tr><tr style="vertical-align:baseline;"><td>Surface gravity (log g)</td><td>4.33<ref name="Adelman2004" /> cgs</td></tr><tr style="vertical-align:baseline;"><td>Temperature</td><td>9,940<ref name="Adelman2004" /> K</td></tr><tr style="vertical-align:baseline;"><td>Metallicity [Fe/H]</td><td>0.50<ref name="Qiu2001" /> dex</td></tr><tr style="vertical-align:baseline;"><td>Rotation</td><td>16 km/s<ref name="Royer2002" /></td></tr><tr style="vertical-align:baseline;"><td>Age</td><td>225–250<ref name="Liebert2005" /> Myr</td></tr><tr><th colspan="2" style="text-align: center">α CMa B</th></tr><tr style="vertical-align:baseline;"><td>Mass</td><td>0.978<ref name="Liebert2005" /> M</td></tr><tr style="vertical-align:baseline;"><td>Radius</td><td>0.0084 ± 3%<ref name="Holberg1998" /> R</td></tr><tr style="vertical-align:baseline;"><td>Luminosity</td><td>0.056<ref name=sweeney>{{#invoke:Citation/CS1|citation

CitationClass=journal

}}</ref> </td></tr><tr style="vertical-align:baseline;"><td>Surface gravity (log g)</td><td>8.57<ref name="Holberg1998" /> cgs</td></tr><tr style="vertical-align:baseline;"><td>Temperature</td><td>25,200<ref name="Liebert2005" /> K</td></tr> <tr><th style="background-color: #FFFFC0; text-align: center;" colspan="2">Database references</th></tr><tr style="vertical-align: top;"><td>SIMBAD</td><td>The system</tr><tr style="vertical-align: top;"><td></td><td>A</tr><tr style="vertical-align: top;"><td></td><td>B</tr>

Sirius ({{#invoke:IPAc-en|main}}) is the brightest star (in fact, a star system) in the Earth's night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name "Sirius" is derived from the Ancient Greek Σείριος (Seirios), meaning "glowing" or "scorcher". The system has the Bayer designation Alpha Canis Majoris (α CMa). What the naked eye perceives as a single star is actually a binary star system, consisting of a white main-sequence star of spectral type A1V, termed Sirius A, and a faint white dwarf companion of spectral type DA2, called Sirius B. The distance separating Sirius A from its companion varies between 8.2 and 31.5 AU.<ref name="Schaaf2008" />

Sirius appears bright because of both its intrinsic luminosity and its proximity to Earth. At a distance of 2.6 parsecs (8.6 ly), as determined by the Hipparcos astrometry satellite,<ref name="aaa474_2_653" /><ref name=aaa323_L49>{{#invoke:citation/CS1|citation

CitationClass=citation

}}</ref><ref name=GSM>{{#invoke:citation/CS1|citation

CitationClass=citation

}}</ref> the Sirius system is one of Earth's near neighbors. Sirius is gradually moving closer to the Solar System, so it will slightly increase in brightness over the next 60,000 years. After that time its distance will begin to increase, but it will continue to be the brightest star in the Earth's sky for the next 210,000 years.<ref>Sky and Telescope, April 1998 (p60), based on computations from Hipparcos data.</ref>

Sirius A is about twice as massive as the Sun (M) and has an absolute visual magnitude of 1.42. It is 25 times more luminous than the Sun<ref name="Liebert2005" /> but has a significantly lower luminosity than other bright stars such as Canopus or Rigel. The system is between 200 and 300 million years old.<ref name="Liebert2005" /> It was originally composed of two bright bluish stars. The more massive of these, Sirius B, consumed its resources and became a red giant before shedding its outer layers and collapsing into its current state as a white dwarf around 120 million years ago.<ref name="Liebert2005" />

Sirius is also known colloquially as the "Dog Star", reflecting its prominence in its constellation, Canis Major (Greater Dog).<ref name="Allen1899" /> 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.


Sirius sections
Intro   Observational history    Visibility    System    Etymology and cultural significance    See also    Notes    References    External links   

PREVIOUS: IntroNEXT: Observational history
<<>>