Universe Guide

Sirius (Alpha Canis Majoris, 9 Canis Majoris) Star Facts

Sirius Facts

  • Sirius is a multiple star system that can be located in the constellation of Canis Major. The description is based on the spectral class.
  • Sirius is a main star of the constellation outline.
  • Based on the spectral type (A0m...) of the star, the star's colour is blue - white .
  • Sirius is the brightest star in the night sky and the brightest star in Canis Major based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.
  • The star is calculated at being about 8.60 light years away from us. Distance

Information on Sirius

Sirius is also known as the Dog star, after all it is in the Big Dog constellation of Canis Major. It is widely known in part as it is the brightest star in the night sky, it is almost twice as bright as the next brightest star, Canopus. It is also one of our nearest neighbour stars, not as close as Rigil Kentaurus (Alpha Centauri) but still close. The only thing that is brighter excluding the moon is the planet Venus. It is moving closer towards us but won't for a long time, longer than you and I will be on this planet so nothing to worry.

Sirius is a Double Star System with the smaller star being a white dwarf star having used up all its hydrogen. The smaller star was not discovered until 1862.

Brightest Star in the Night Sky

When we look up at the night sky, the brightest star we can see is Sirius (assuming clear sky and in the right location). However if we are talking about brightest in terms of Luminosity and not necessarily visible brightest, then the most luminous we know of is R136a1 which in a nearby galaxy.

Sirius in Fiction

Being the brightest and one of the most well known, it has become of interest by science fiction writers, for example, the lizard Visitors from V come from a planet orbiting this star. JK Rowling, author of the Harry Potter books has a character Sirius Black who name is inspired from this star. There are also other stars that have been the inspiration for characters such as Regulus Black. Sirius isn't just limited to being mentioned in these fictions, the star is mentioned elsewhere. Sirius gets mentioned in Star Trek but there's no real stories based in the Sirius Solar System excluding the cartoon series and extended Universe. ref:Memory Alpha.

Sirius on the Move

Sirius is currently moving towards us but don't fear a solar apocalypse, it will never collide with our Sun. It is moving at a very slow speed of 5.5 km/s and the closest it will ever get to us is 7.8 Light years, down from 8.6 that it is now. It will continue to be the brightest star in the night sky for at least another 90000 year after which point Delta Scuti will then take on that title. ref:StackExchange

Sirius's Alternative Names

Alpha Canis Majoris (Alf Cma) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in 1603. The brightest star in the constellation is normally given the Alpha designation, there are exceptions such as Pollux which is Beta Geminorum.

The Id of the star in the Yale Bright Star Catalogue is HR2491. HIP32349 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD48915. The Gliese ID of the star is GL 244A. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Star Names

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John named the stars in the constellation with a number and its latin name, this star's Flamsteed designation is 9 Canis Majoris. The Flamsteed name can be shortened to 9 Cma.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD-16 1591.

More details on objects' alternative names can be found at Star Names .

Location of Sirius

The location of the multiple star system in the night sky is determined by the Right Ascension (R.A.) and Declination (Dec.), these are equivalent to the Longitude and Latitude on the Earth. The Right Ascension is how far expressed in time (hh:mm:ss) the star is along the celestial equator. If the R.A. is positive then its eastwards. The Declination is how far north or south the object is compared to the celestial equator and is expressed in degrees. For Sirius, the location is 06h 45m 09.25 and -16° 42` 47.3 .

Radial Velocity and Proper Motion of Sirius

Proper Motion

All stars like planets orbit round a central spot, in the case of planets, its the central star such as the Sun. In the case of a star, its the galactic centre. The constellations that we see today will be different than they were 50,000 years ago or 50,000 years from now. Proper Motion details the movements of these stars and are measured in milliarcseconds. The star is moving -1,223.07 ± 1.04 milliarcseconds/year towards the north and -546.01 ± 1.58 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is -5.50000 km/s with an error of about 0.40 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Physical Properties of Sirius

Sirius Colour and Temperature

Based on the star's spectral type of A0m... , Sirius's colour and type is blue - white multiple star system. The star's effective temperature is 9,580 Kelvin which is hotter than our own Sun's effective Temperature which is 5,777 Kelvin.

Sirius Luminosity

Luminosity is the amount of energy that a star pumps out and its relative to the amount that our star, the Sun gives out. The figure of 25.84 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Sirius Radius

Sirius estimated radius has been calculated as being 1.29 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 897,444.94.km. If you need the diameter of the star, you just need to multiple the radius by 2. The figure is derived at by using the formula from SDSS rather than peer reviewed papers. It has been known to produce widely incorrect figures.

Sirius Iron Abundance

Sirius Iron Abundance is 0.36 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context. The value comes from the Hipparcos Extended Catalog.

Sirius Apparent and Absolute Magnitudes

Sirius has an apparent magnitude of -1.44 which is how bright we see the star from Earth. Apparent Magnitude is also known as Visual Magnitude. Using the supplied Parallax value, you would get an absolute magnitude of 1.45 Magnitude, whether it be apparent/visual or absolute magnitude is measured by a number, the smaller the number, the brighter the Star is. Our own Sun is the brightest star and therefore has the lowest of all magnitudes, -26.74. A faint star will have a high number.

Distance to Sirius

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 379.21000 which gave the calculated distance to Sirius as 8.60 light years away from Earth or 2.64 parsecs. If you want that in miles, it is about 50,556,178,209,379.05, based on 1 Ly = 5,878,625,373,183.61 miles.

The star's Galacto-Centric Distance is 7,402.00 Parsecs or 24,142.61 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Travel Time to Sirius

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Airbus A3807367,836,009.52
Speed of Sound (Mach 1)767.2697,516,663.66
Concorde (Mach 2)1,534.543,758,326.93
New Horizons Probe33,000174,766.76
Speed of Light670,616,629.008.60

Source of Information

The source of the information if it has a Hip I.D. is from Simbad, the Hipparcos data library based at the University at Strasbourg, France. Hipparcos was a E.S.A. satellite operation launched in 1989 for four years. The items in red are values that I've calculated so they could well be wrong. Information regarding Metallicity and/or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Hide Explanations
Show GridLines

Additional Sirius Facts and Figures

Visual Facts

Primary / Proper / Traditional NameSirius
Alternative NamesAlpha Canis Majoris, Alf Cma, HD 48915, HIP 32349, HR 2491, 9 Canis Majoris, 9 Cma, BD-16 1591, Gliese 244A
Spectral TypeA0m...
Constellation's Main StarYes
Multiple Star SystemYes
Star TypeMultiple Star System
GalaxyMilky Way
ConstellationCanis Major
Absolute Magnitude 1.45
Visual / Apparent Magnitude-1.44
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)06h 45m 09.25
Declination (Dec.)-16° 42` 47.3
Galactic Latitude-8.88779442 degrees
Galactic Longitude227.22816026 degrees
Distance from Earth379.21000 Parallax (milliarcseconds)
 8.60 Light Years
 2.64 Parsecs
 544,535.29 Astronomical Units
Galacto-Centric Distance24,142.61 Light Years / 7,402.00 Parsecs
Proper Motion Dec.-1223.07000 ± 1.04000 milliarcseconds/year
Proper Motion RA.-546.01000 ± 1.58000 milliarcseconds/year
B-V Index-0.03
Radial Velocity-5.50000 ± 0.40 km/s
Iron Abundance0.3600 ± 9.99 Fe/H
Semi-Major Axis8476.0000000
Stellar Luminosity (Lsun)25.8400000
Orbital Period (Days)18295.40000
Argument Of Periastron327.27000
Brightest in Night Sky1st
Associated / Clustered StarsSirius A
Sirius B

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Estimated Calculated Facts

Radius (x the Sun)1.29
Effective Temperature11,122 Kelvin

Sources and Links

SIMBAD SourceLink

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.

Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
48915-16 1591.0A-1.60000-553.00000-1205.00000A0White

Location of Sirius in Canis Major

Sirius Location in Canis Major

The map was generated using Night Vision, an awesome free application by Brian Simpson.

Canis Major Main Stars

Comments and Questions

There's no register feature and no need to give an email address if you don't need to. All messages will be reviewed before being displayed. Comments may be merged or altered slightly such as if an email address is given in the main body of the comment.

You can decline to give a name which if that is the case, the comment will be attributed to a random star. A name is preferred even if its a random made up one by yourself.


Betty BooSaturday, 24th August 2019 3:32:43 PM
What is Sirius's luminosity?
This website is using cookies. More info. That's Fine