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21 Sextantis, HD88764, HIP50140

21 Sextantis is a orange to red star that can be located in the constellation of Sextans. The star can not be seen by the naked eye, you need a telescope to see it.

21 Sextantis's Alternative Names

HIP50140 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD88764.

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 Sextantis with it shortened to 21 Sex.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD-07 2989.

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

Location of 21 Sextantis

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 21 Sextantis, the location is 10h 14m 08.41 and -07° 59` 36.4 .

Proper Motion of 21 Sextantis

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 -21.81 ± 0.35 miliarcseconds/year towards the north and -11.78 ± 0.54 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 us is 9.30000 km/s with an error of about 3.00 km/s .

21 Sextantis 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 127.5200000 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature) of 21 Sextantis

21 Sextantis has a spectral type of K0. This means the star is a orange to red star. The star is 7471.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24367.6634302400000000s. The star has a B-V Colour Index of 1.03 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,908 Kelvin.

21 Sextantis Radius has been calculated as being 10.79 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 7,508,875.32.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 13.34. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

21 Sextantis Apparent and Absolute Magnitudes

21 Sextantis has an apparent magnitude of 6.97 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 0.39 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.07. 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 21 Sextantis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 4.83 which gave the calculated distance to 21 Sextantis as 675.29 light years away from Earth or 207.04 parsecs. It would take a spaceship travelling at the speed of light, 675.29 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 3.91 which put 21 Sextantis at a distance of 834.18 light years or 255.75 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 7,471.00 Parsecs or 24,367.66 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.

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21 Sextantis Facts

Visual Facts

Alternative NamesHD 88764, HIP 50140, 21 Sex, BD-07 2989
Star TypeStar
GalaxyMilky Way
Absolute Magnitude0.39 / -0.07
Visual / Apparent Magnitude6.97
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)10h 14m 08.41
Declination (Dec.)-07° 59` 36.4
Galactic Latitude38.20 degrees
Galactic Longitude249.94 degrees
1997 Distance from Earth4.83 Parallax (milliarcseconds)
 675.29 Light Years
 207.04 Parsecs
2007 Revised Distance from Earth3.91 Parallax (milliarcseconds)
 834.18 Light Years
 255.75 Parsecs
Galacto-Centric Distance24,367.66 Light Years / 7,471.00 Parsecs
Proper Motion Dec.-21.81 ± 0.35 milliarcseconds/year
Proper Motion RA.-11.78 ± 0.54 milliarcseconds/year
B-V Index1.03
Radial Velocity9.30 ± 3.00 km/s
Semi-Major Axis6776.00
Stellar Luminosity (Lsun)127.52
Spectral TypeK0
Colour(K) Orange to Red

Estimated Facts

Calculated Effective Temperature4,908 Kelvin

Sources and Links

SIMBAD SourceLink

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