Universe Guide


55 Sagittarii, HD186005, HIP96950

55 Sagittarii is a blue to white subgiant star that can be located in the constellation of Sagittarius. 55 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.

HIP96950 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD186005. The Id of the star in the Gould Star Catalogue is 225. 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 55 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 55 Sagittarii, the location is 19h 42m 31.09 and -16d07`26.3 .

Proper Motion of 55 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 -9.67 ± 0.14 miliarcseconds/year towards the north and 66.29 ± 0.26 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of 55 Sagittarii

55 Sagittarii has a spectral type of F3IV/V. This means the star is a blue to white subgiant star. The star is 7353.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23982.7906843200000000s. The star has a B-V Colour Index of 0.31 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,167 Kelvin.

55 Sagittarii Radius has been calculated as being 3.15 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,191,286.08.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 3.19. 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 -0.20 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

55 Sagittarii Apparent and Absolute Magnitudes

55 Sagittarii has an apparent magnitude of 5.06 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 1.42 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.39. 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 55 Sagittarii

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 18.67 which gave the calculated distance to 55 Sagittarii as 174.70 light years away from Earth or 53.56 parsecs. It would take a spaceship travelling at the speed of light, 174.70 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 18.41 which put 55 Sagittarii at a distance of 177.17 light years or 54.32 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 7,353.00 Parsecs or 23,982.79 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.

55 Sagittarii Facts

Alternative Names

Traditional/Proper Name55 Sagittarii
Flamsteed Name55 Sagittarii
Flamsteed Short Name55 Sgr
Hipparcos Library I.D.96950
Bonner DurchmusterungBD-16 5413
Gould I.D.225
Henry Draper Designation186005

Visual Facts

Star Typesubgiant star
Absolute Magnitude1.42 / 1.39
Visual / Apparent Magnitude5.06
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)19h 42m 31.09
Declination (Dec.)-16d07`26.3
Galactic Latitude-18.40 degrees
Galactic Longitude23.82 degrees
1997 Distance from Earth18.67 Parallax (milliarcseconds)
 174.70 Light Years
 53.56 Parsecs
2007 Revised Distance from Earth18.41 Parallax (milliarcseconds)
 177.17 Light Years
 54.32 Parsecs
Galacto-Centric Distance23,982.79 Light Years / 7,353.00 Parsecs
Proper Motion Dec.-9.67 ± 0.14 milliarcseconds/year
Proper Motion RA.66.29 ± 0.26 milliarcseconds/year
B-V Index0.31
Radial Velocity-32.00 ± 3.40 km/s
Iron Abundance-0.20 ± 9.99 Fe/H
Spectral TypeF3IV/V
Colour(F) blue to white

Estimated Facts

Calculated Effective Temperature7,167 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
186005-16 5413.0A6.3000063.00000-10.00000F0Yellow/White

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