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21 Piscium, HD223438, HIP117491, HR9022

21 Piscium is a blue star that can be located in the constellation of Pisces. 21 Piscium is the brightest star in Pisces 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 HR9022. HIP117491 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD223438. The Id of the star in the Gould Star Catalogue is 46. 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 21 Piscium

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 Piscium, the location is 23h 49m 27.48 and +01d 04` 34.3 .

Proper Motion of 21 Piscium

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 -27.07 ± 0.23 miliarcseconds/year towards the north and -1.24 ± 0.37 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 9.50000 km/s with an error of about 1.00 km/s .

Physical Properties (Colour, Temperature, Radius) of 21 Piscium

21 Piscium has a spectral type of A5m. This means the star is a blue star. The star is 7403.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24145.8723563200000000s. The star has a B-V Colour Index of 0.16 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,747 Kelvin.

21 Piscium Radius has been calculated as being 2.98 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,075,434.05.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 3.38. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

21 Piscium Apparent and Absolute Magnitudes

21 Piscium has an apparent magnitude of 5.77 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 1.20 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.93. 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 Piscium

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 12.19 which gave the calculated distance to 21 Piscium as 267.57 light years away from Earth or 82.03 parsecs. It would take a spaceship travelling at the speed of light, 267.57 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 10.74 which put 21 Piscium at a distance of 303.69 light years or 93.11 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 7,403.00 Parsecs or 24,145.87 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.

21 Piscium Facts

Alternative Names

Traditional/Proper Name21 Piscium
Flamsteed Name21 Piscium
Flamsteed Short Name21 Psc
Hipparcos Library I.D.117491
Yale Bright Star Catalogue (HR) Id9022
Bonner DurchmusterungBD+00 5054
Gould I.D.46
Henry Draper Designation223438

Visual Facts

Star Type star
Absolute Magnitude1.20 / 0.93
Visual / Apparent Magnitude5.77
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)23h 49m 27.48
Declination (Dec.)+01d 04` 34.3
Galactic Latitude-58.09 degrees
Galactic Longitude92.57 degrees
1997 Distance from Earth12.19 Parallax (milliarcseconds)
 267.57 Light Years
 82.03 Parsecs
2007 Revised Distance from Earth10.74 Parallax (milliarcseconds)
 303.69 Light Years
 93.11 Parsecs
Galacto-Centric Distance24,145.87 Light Years / 7,403.00 Parsecs
Proper Motion Dec.-27.07 ± 0.23 milliarcseconds/year
Proper Motion RA.-1.24 ± 0.37 milliarcseconds/year
B-V Index0.16
Radial Velocity9.50 ± 1.00 km/s
Spectral TypeA5m
Colour(A) blue

Estimated Facts

Calculated Effective Temperature7,747 Kelvin

Sources and Links

SIMBAD SourceLink

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