Universe Guide

Nu Hydri

Nu Hydri Facts

Nu Hydri's Alternative Names

Nu Hydri (Nu. Hyi) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in 1603. The brightest star in the constellation is normally given the Alpha designation, there are exceptions such as Pollux which is Beta Geminorum.

The Id of the star in the Yale Bright Star Catalogue is HR872. HIP13244 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD18293.

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

Location of Nu 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 Nu Hydri, the location is 02h 50m 28.54 and -75° 04` 00.8 .

Radial Velocity and Proper Motion of Nu 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 -27.30 ± 0.15 milliarcseconds/year towards the north and -33.01 ± 0.16 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 4.70 km/s with an error of about 0.80 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.

Nu 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 240.69 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 Nu Hydri

Nu Hydri Colour and Temperature

Nu Hydri has a spectral type of K3III. This means the star is a orange to red giant star. The star has a B-V Colour Index of 1.33 which means the star's temperature is about 4,273 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu at being .

Nu Hydri Radius

Radius has been calculated as being 19.21 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 13,363,634.75.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 19.84. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Nu Hydri Apparent and Absolute Magnitudes

Nu Hydri has an apparent magnitude of 4.76 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 -0.26 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.33. 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 Nu Hydri

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 9.92 which gave the calculated distance to Nu Hydri as 328.79 light years away from Earth or 100.81 parsecs. If you want that in miles, it is 220,492,041,449.

In 2007, Hipparcos data was revised with a new parallax of 9.61 which put Nu Hydri at a distance of 339.40 light years or 104.06 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 21,463,766.18 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 7,369.00 Parsecs or 24,034.98 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 Nu 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 A380736309,249,027.01
Speed of Sound (Mach 1)767.269296,646,005.35
Concorde (Mach 2)1,534.54148,322,809.36
New Horizons Probe33,0006,897,190.42
Speed of Light670,616,629.00339.40

Meteor Showers Radiating from near Nu Hydri

The nu Hydrids Meteor Shower radiants from a point near this star. The meteor shower runs typically between with a peak date of 19th March. The speed of a meteor in the shower is 20 Km/s.

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 Nu Hydri Facts and Figures

Visual Facts

Primary / Proper / Traditional NameNu Hydri
Alternative NamesNu. Hyi, HD 18293, HIP 13244, HR 872
Spectral TypeK3III
Constellation's Main StarYes
Multiple Star SystemNo / Unknown
Star TypeGiant Star
ColourOrange to Red
GalaxyMilky Way
Absolute Magnitude -0.26 / -0.33
Visual / Apparent Magnitude4.76
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)02h 50m 28.54
Declination (Dec.)-75° 04` 00.8
Galactic Latitude-39.77 degrees
Galactic Longitude293.35 degrees
1997 Distance from Earth9.92 Parallax (milliarcseconds)
 328.79 Light Years
 100.81 Parsecs
2007 Distance from Earth9.61 Parallax (milliarcseconds)
 339.40 Light Years
 104.06 Parsecs
 21,463,766.18 Astronomical Units
Galacto-Centric Distance24,034.98 Light Years / 7,369.00 Parsecs
Proper Motion Dec.-27.30 ± 0.15 milliarcseconds/year
Proper Motion RA.-33.01 ± 0.16 milliarcseconds/year
B-V Index1.33
Radial Velocity4.70 ± 0.80 km/s
Semi-Major Axis8990.00
Stellar Luminosity (Lsun)240.69

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Estimated Calculated Facts

Radius (x the Sun)19.84
Effective Temperature4,273 Kelvin

Sources and Links

SIMBAD SourceLink

Hydrus Main Stars

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