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Rho2 Sagittarii, 45 Sagittarii, HD181645, HIP95188, HR7344

Rho2 Sagittarii is a orange to red giant star that can be located in the constellation of Sagittarius. Rho2 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.

Rho2 Sagittarii is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR7344. HIP95188 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD181645. The Id of the star in the Gould Star Catalogue is 175. 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 Rho2 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 Rho2 Sagittarii, the location is 19h 21m 50.83 and -18d 18` 29.4 .

Proper Motion of Rho2 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 -93.20 ± 0.25 miliarcseconds/year towards the north and 102.72 ± 0.40 miliarcseconds/year east if we saw them in the horizon.

Rho2 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 96.0000000 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 Rho2 Sagittarii

Rho2 Sagittarii has a spectral type of K0III. This means the star is a orange to red giant star. The star is 7308.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23836.0171795200000000s. The star has a B-V Colour Index of 1.06 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,736 Kelvin.

Rho2 Sagittarii Radius has been calculated as being 10.38 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 7,220,350.13.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 9.60. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Rho2 Sagittarii Apparent and Absolute Magnitudes

Rho2 Sagittarii has an apparent magnitude of 5.84 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 0.63 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.80. 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 Rho2 Sagittarii

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 9.09 which gave the calculated distance to Rho2 Sagittarii as 358.82 light years away from Earth or 110.01 parsecs. It would take a spaceship travelling at the speed of light, 358.82 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 9.82 which put Rho2 Sagittarii at a distance of 332.14 light years or 101.83 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 7,308.00 Parsecs or 23,836.02 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.

Rho2 Sagittarii Facts

Alternative Names

Flamsteed Name45 Sagittarii
Flamsteed Short Name45 Sgr
Bayer DesignationRho2 Sagittarii
Hipparcos Library I.D.95188
Yale Bright Star Catalogue (HR) Id7344
Bonner DurchmusterungBD-18 5325
Gould I.D.175
Henry Draper Designation181645

Visual Facts

Star Typegiant star
Absolute Magnitude0.63 / 0.80
Visual / Apparent Magnitude5.84
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)19h 21m 50.83
Declination (Dec.)-18d 18` 29.4
Galactic Latitude-14.77 degrees
Galactic Longitude19.64 degrees
1997 Distance from Earth9.09 Parallax (milliarcseconds)
 358.82 Light Years
 110.01 Parsecs
2007 Revised Distance from Earth9.82 Parallax (milliarcseconds)
 332.14 Light Years
 101.83 Parsecs
Galacto-Centric Distance23,836.02 Light Years / 7,308.00 Parsecs
Proper Motion Dec.-93.20 ± 0.25 milliarcseconds/year
Proper Motion RA.102.72 ± 0.40 milliarcseconds/year
B-V Index1.06
Radial Velocity-12.70 ± 2.90 km/s
Spectral TypeK0III
Colour(K) Orange to Red

Estimated Facts

Luminosity (x the Sun)96.0000000
Calculated Effective Temperature4,736 Kelvin

Sources and Links

SIMBAD SourceLink

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