Universe Guide

BN Hydri

BN Hydri Facts

  • BN Hydri is a giant star that can be located in the constellation of Hydrus. The description is based on the spectral class.
  • BN Hydri is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (F2II-III) of the star, the star's colour is yellow to white .
  • The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 270.23 light years away from us. Distance

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 objects' alternative names can be found at Star Names .

Location of BN Hydri

The location of the giant 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 object 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 .

Radial Velocity and Proper Motion of BN Hydri

Proper Motion

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 milliarcseconds/year towards the north and 80.80 ± 0.58 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is 11.00 km/s with an error of about 7.40 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Physical Properties of BN Hydri

BN Hydri Temperature and Colour

Based on the star's spectral type of F2II-III , BN Hydri's colour and type is yellow to white giant star. The star has a B-V Colour Index of 0.29 which means the star's temperature is about 7,270 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

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.

BN Hydri Radius

BN Hydri estimated 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 rather than peer reviewed papers. It 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. If you want that in miles, it is about 1,460,309,328,952,540.56, based on 1 Ly = 5,878,625,373,183.61 miles.

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.

Using the 2007 distance, the star is roughly 17,088,920.12 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun. 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*.

Travel Time to BN Hydri

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Airbus A380736246,223,820.18
Speed of Sound (Mach 1)767.269236,189,304.73
Concorde (Mach 2)1,534.54118,094,498.45
New Horizons Probe33,0005,491,537.32
Speed of Light670,616,629.00270.23

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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Additional BN Hydri Facts and Figures

Visual Facts

Primary / Proper / Traditional NameBN Hydri
Alternative NamesHD 20313, HIP 14521
Spectral TypeF2II-III
Constellation's Main StarNo
Multiple Star SystemYes
Star TypeGiant Star
ColourYellow - White
GalaxyMilky Way
Absolute Magnitude 1.26 / 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
 17,088,920.12 Astronomical Units
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
Semi-Major Axis6839.00
Stellar Luminosity (Lsun)30.49

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Estimated Calculated Facts

Radius (x the Sun)3.58
Effective Temperature7,270 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Comments and Questions

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