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15 Sagittarii, HD167264, HIP89439, HR6822

15 Sagittarii is a blue very luminous supergiant star that can be located in the constellation of Sagittarius. 15 Sagittarii is the brightest star in Sagittarius 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 Id of the star in the Yale Bright Star Catalogue is HR6822. HIP89439 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD167264. The Id of the star in the Gould Star Catalogue is 43. Stars in the southern hemisphere are more likely to have a Gould Id than the northern hemisphere. For example, there are no Gould classified stars in Ursa Major.

Location of 15 Sagittarii

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 15 Sagittarii, the location is 18h 15m 12.91 and -20d 43` 41.8 .

Proper Motion of 15 Sagittarii

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 -1.51 ± 0.33 miliarcseconds/year towards the north and 1.60 ± 0.45 miliarcseconds/year east if we saw them in the horizon.

15 Sagittarii 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 320000.0000000 that I have given is based on the Spectral Types page that I have found on the Internet. You might find a different figure, one that may have been calculated rather than generalised that I have done. The figure is always the amount times the luminosity of the Sun. It is an imprecise figure because of a number of factors including but not limited to whether the star is a variable star and distance.

Physical Properties (Colour, Temperature, Radius) of 15 Sagittarii

15 Sagittarii has a spectral type of B0/1Ia/ab. This means the star is a blue supergiant star. The star has a B-V Colour Index of 0 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 10,293 Kelvin. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

15 Sagittarii Apparent and Absolute Magnitudes

15 Sagittarii has an apparent magnitude of 5.29 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 If you used the 2007 Parallax value, you would get an absolute magnitude of -9.71. 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 15 Sagittarii

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as -0.33 which gave the calculated distance to 15 Sagittarii as -9883.74 light years away from Earth or -3030.30 parsecs. It would take a spaceship travelling at the speed of light, -9883.74 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 0.10 which put 15 Sagittarii at a distance of 32616.33 light years or 10000 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. 15 Sagittarii brightness ranges from a magnitude of 5.366 to a magnitude of 5.332 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.0 days (variability).

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.

15 Sagittarii Facts

Alternative Names

Traditional/Proper Name15 Sagittarii
Flamsteed Name15 Sagittarii
Flamsteed Short Name15 Sgr
Hipparcos Library I.D.89439
Yale Bright Star Catalogue (HR) Id6822
Bonner DurchmusterungBD-20 5054
Gould I.D.43
Henry Draper Designation167264

Visual Facts

Star Typesupergiant star
Visual / Apparent Magnitude5.29
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)18h 15m 12.91
Declination (Dec.)-20d 43` 41.8
Galactic Latitude-1.74 degrees
Galactic Longitude10.46 degrees
1997 Distance from Earth-0.33 Parallax (milliarcseconds)
 -9883.74 Light Years
 -3030.30 Parsecs
2007 Revised Distance from Earth0.10 Parallax (milliarcseconds)
 32616.33 Light Years
 10000 Parsecs
Proper Motion Dec.-1.51 ± 0.33 milliarcseconds/year
Proper Motion RA.1.60 ± 0.45 milliarcseconds/year
B-V Index0.00
Radial Velocity-6.30 ± 2.80 km/s
Spectral TypeB0/1Ia/ab
Colour(B) blue

Variable Star Details

Mean Variability Period in Days0.037
Variable Magnitude Range (Brighter - Dimmer)5.332 - 5.366

Estimated Facts

Luminosity (x the Sun)320,000.0000000
Calculated Effective Temperature10,293 Kelvin

Sources and Links

SIMBAD SourceLink

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