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Antares, Alpha Scorpii, 21 Scorpii, HD148478, HIP80763, HR6134

Antares (Alpha Scorpii) Location in Scorpius

Antares (Alpha Scorpii) is a red pulsating main sequence dwarf star that can be located in the constellation of Scorpius. The description is based on the spectral class. Antares is a main star of the constellation.

Antares is the 15th brightest star in the night sky and is the brightest star in Scorpius 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.

Antares's Alternative Names

Alpha Scorpii (Alf Sco) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR6134. HIP80763 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD148478.

Antares has alternative name(s) :- , alf Sco.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John numbered the stars in the constellation with a number and the latin name, this star's Flamsteed designation is 21 Scorpii with it shortened to 21 Sco.

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

Location of Antares

The location of the star 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 star is compared to the celestial equator and is expressed in degrees. For Antares, the location is 16h 29m 24.47 and -26° 25` 55.0 .

Radial Velocity and Proper Motion of Antares

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 -23.30 ± 0.58 miliarcseconds/year towards the north and -12.11 ± 1.00 miliarcseconds/year east if we saw them in the horizon.

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is -3.50 km/s with an error of about 0.80 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 (Colour, Temperature, Radius) of Antares

Antares has a spectral type of M1Ib + B2.5V. This means the star is a red main sequence dwarf star. The star is 7,243.00 Parsecs from the Galactic Centre or terms of Light Years is 23,624.01 s. The star has a B-V Colour Index of 1.86 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 2,498 Kelvin.

Antares has been calculated as 883.00 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 614,391,400.00.km. If you need the diameter of the star, you just need to multiple the radius by 2.

Antares Apparent and Absolute Magnitudes

Antares has an apparent magnitude of 1.06 which is how bright we see the star from Earth. Apparent Magnitude is also known as Visual Magnitude. If you used the 1997 Parallax value, you would get an absolute magnitude of -5.28 If you used the 2007 Parallax value, you would get an absolute magnitude of -5.09. 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 Antares

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 5.40 which gave the calculated distance to Antares as 604.01 light years away from Earth or 185.19 parsecs. It would take a spaceship travelling at the speed of light, 604.01 years to get there. We don't have the technology or spaceship that can carry people over that distance yet.

In 2007, Hipparcos data was revised with a new parallax of 5.89 which put Antares at a distance of 553.76 light years or 169.78 parsecs. It should not be taken as though the star is moving closer or further away from us. It is purely that the distance was recalculated.

The star's Galacto-Centric Distance is 7,243.00 Parsecs or 23,624.01 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of Antares

The star is a pulsating Slow Irregular variable type which means that its size changes over time. The Variable Type is usually named after the first star of that type to be spotted. Antares brightness ranges from a magnitude of 1.067 to a magnitude of 0.906 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 days (variability).

Meteor Showers Radiating from near Antares

The Alpha Scorpiids Meteor Shower radiants from a point near this star. The meteor shower runs typically between 21 Apr- 26 May with a peak date of 15-May. The speed of a meteor in the shower is 35 Km/s. The amount of meteors predicted to be seen per hour (Zenith Hourly Rate) is 35.

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.

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Antares Facts

Visual Facts


Primary / Proper / Traditional NameAntares
Alternative NamesAlpha Scorpii, Alf Sco, HD 148478, HIP 80763, HR 6134, 21 Scorpii, 21 Sco, alf Sco
Spectral TypeM1Ib + B2.5V
Constellation's Main StarYes
Multiple Star SystemYes
Star Type main sequence Dwarf Star
Colour red
GalaxyMilky Way
ConstellationScorpius
Absolute Magnitude -5.28 / -5.09
Visual / Apparent Magnitude1.06
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)16h 29m 24.47
Declination (Dec.)-26° 25` 55.0
Galactic Latitude15.06 degrees
Galactic Longitude351.95 degrees
1997 Distance from Earth5.40 Parallax (milliarcseconds)
 604.01 Light Years
 185.19 Parsecs
2007 Distance from Earth5.89 Parallax (milliarcseconds)
 553.76 Light Years
 169.78 Parsecs
Galacto-Centric Distance23,624.01 Light Years / 7,243.00 Parsecs
Proper Motion Dec.-23.30 ± 0.58 milliarcseconds/year
Proper Motion RA.-12.11 ± 1.00 milliarcseconds/year
B-V Index1.86
Radial Velocity-3.50 ± 0.80 km/s
Eccentricity0.08
Semi-Major Axis6794.00
Brightest in Night Sky15th

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeSlow Irregular
Mean Variability Period in Days0.134
Variable Magnitude Range (Brighter - Dimmer)0.906 - 1.067

Estimated Facts


Radius (x the Sun)883.00
Calculated Effective Temperature2,498 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
148478-2611359.2A1.20000-6.00000-23.00000M1Red
148479B5.40000B3Blue/White1959

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