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Alsafi (Sigma Draconis) - HD185144 - HIP96100

Alsafi (Sigma Draconis) is a orange to red main sequence dwarf star that can be located in the constellation of Draco. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Sigma Draconis is the Bayer Classification for the star. HIP96100 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD185144. The Gliese ID of the star is Gliese GL764. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Ref : Star Names.

Alsafi has alternative name(s), 61 Draconis , 61 Dra.

Location of Alsafi

The location of the star in the galaxy 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 Alsafi, the location is 19h 32m 20.59 and +69d39`55.4 .

Proper Motion of Alsafi

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 -1,738.40 ± 0.17 miliarcseconds/year towards the north and 598.07 ± 0.18 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Alsafi

Alsafi has a spectral type of K0V. This means the star is a orange to red main sequence dwarf star. The star is 7401.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24139.3490894400000000s. The star has a B-V Colour Index of 0.78 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,337 Kelvin.

Alsafi Radius has been calculated as being 0.73 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 511,370.76.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 0.73. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is -0.19 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Alsafi Apparent and Absolute Magnitudes

Alsafi has an apparent magnitude of 4.67 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 5.86 If you used the 2007 Parallax value, you would get an absolute magnitude of 5.87. 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 Alsafi

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 173.41 which gave the calculated distance to Alsafi as 18.81 light years away from Earth or 5.77 parsecs. It would take a spaceship travelling at the speed of light, 18.81 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 173.77 which put Alsafi at a distance of 18.77 light years or 5.75 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 7,401.00 Parsecs or 24,139.35 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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.

Alsafi Facts

Alternative Names

Traditional/Proper NameAlsafi
Short Name61 Dra
Bayer DesignationSigma Draconis
Alternative Name(s)61 Draconis
Hipparcos Library I.D.96100
Bonner DurchmusterungBDD+69 1053
Gliese ID764
Henry Draper Designation185144

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude5.86 / 5.87
Visual / Apparent Magnitude4.67
Naked Eye VisibleYes - Ref: Wiki
Right Ascension (R.A.)19h 32m 20.59
Declination (Dec.)+69d39`55.4
Galactic Latitude21.88 degrees
Galactic Longitude101.31 degrees
1997 Distance from Earth173.41 Parallax (milliarcseconds)
 18.81 Light Years
 5.77 Parsecs
2007 Revised Distance from Earth173.77 Parallax (milliarcseconds)
 18.77 Light Years
 5.75 Parsecs
Galacto-Centric Distance24,139.35 Light Years / 7,401.00 Parsecs
Proper Motion Dec.-1738.40 ± 0.17 milliarcseconds/year
Proper Motion RA.598.07 ± 0.18 milliarcseconds/year
B-V Index0.78
Radial Velocity26.78 ± 0.08 km/s
Iron Abundance-0.19 ± 9.99 Fe/H
Spectral TypeK0V
Colour(K) Orange to Red

Estimated Facts

Calculated Effective Temperature5,337 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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
185144+69 1053.0A4.80000577.00000-1743.00000K0Orange
B1902

Location of Alsafi in Draco


Alsafi (Sigma Draconis) Location in Draco

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


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