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BN Hydri, HD20313, HIP14521

BN Hydri is a blue to white giant star that can be located in the constellation of Hydrus. The description is based on the spectral class. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

BN Hydri's Alternative Names

HIP14521 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD20313.

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

Location of BN Hydri

The location of the star in the night sky 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 BN Hydri, the location is 03h 07m 31.90 and -78° 59` 21.9 .

Proper Motion of BN Hydri

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 73.64 ± 0.60 miliarcseconds/year towards the north and 80.80 ± 0.58 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 11.00000 km/s with an error of about 7.40 km/s .

BN Hydri 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 30.49 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 BN Hydri

BN Hydri has a spectral type of F2II-III. This means the star is a blue to white giant star. The star is 7,372.00 Parsecs from the Galactic Centre or terms of Light Years is 24,044.76 s. The star has a B-V Colour Index of 0.29 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,270 Kelvin.

BN Hydri Radius has been calculated as being 3.29 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,292,485.72.km. If you need the diameter of the star, you just need to multiple the radius by 2. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 3.58. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

BN Hydri Apparent and Absolute Magnitudes

BN Hydri has an apparent magnitude of 5.67 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 1.26 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.08. 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 BN Hydri

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 13.13 which gave the calculated distance to BN Hydri as 248.41 light years away from Earth or 76.16 parsecs. It would take a spaceship travelling at the speed of light, 248.41 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 12.07 which put BN Hydri at a distance of 270.23 light years or 82.85 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 7,372.00 Parsecs or 24,044.76 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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BN Hydri Facts

Visual Facts


Primary / Proper / Traditional NameBN Hydri
Alternative NamesHD 20313, HIP 14521
Spectral TypeF2II-III
Multiple Star SystemYes
Star TypeGiant Star
Colour blue to white
GalaxyMilky Way
ConstellationHydrus
Absolute Magnitude1.26 / 1.08
Visual / Apparent Magnitude5.67
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)03h 07m 31.90
Declination (Dec.)-78° 59` 21.9
Galactic Latitude-36.05 degrees
Galactic Longitude295.34 degrees
1997 Distance from Earth13.13 Parallax (milliarcseconds)
 248.41 Light Years
 76.16 Parsecs
2007 Distance from Earth12.07 Parallax (milliarcseconds)
 270.23 Light Years
 82.85 Parsecs
Galacto-Centric Distance24,044.76 Light Years / 7,372.00 Parsecs
Proper Motion Dec.73.64 ± 0.60 milliarcseconds/year
Proper Motion RA.80.80 ± 0.58 milliarcseconds/year
B-V Index0.29
Radial Velocity11.00 ± 7.40 km/s
Eccentricity0.12
Semi-Major Axis6839.00
Stellar Luminosity (Lsun)30.49

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Estimated Facts


Calculated Effective Temperature7,270 Kelvin

Sources and Links


SIMBAD SourceLink

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