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Tau1 Eridani, 1 Eridani, HD17206, HIP12843, HR818

Tau1 Eridani is a blue to white main sequence dwarf star that can be located in the constellation of Eridanus. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it. The star has an estimated age of 3.00 Billion of Years but could be as young as 2.30 to 3.60 according to Hipparcos.

Tau1 Eridani's Alternative Names

Tau1 Eridani is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR818. HIP12843 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD17206. The Gliese ID of the star is GL 111. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Ref : Star Names.

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 1 Eridani with it shortened to 1 Eri.

The Gould star designation is one that was designed by American astronomer, Benjamin Apthorp Gould. Gould stars are predominantly in the Southern and Equatorial constellations but do appear in northern constellations such as Bootes and Orion. The star has the designation 22 G. Eridani. There are no stars with a Gould designation in Ursa Major for example.

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-19 518.

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

Location of Tau1 Eridani

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 Tau1 Eridani, the location is 02h 45m 05.98 and -18° 34` 21.5 .

Proper Motion of Tau1 Eridani

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 37.19 ± 1.36 miliarcseconds/year towards the north and 334.20 ± 1.83 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 25.90000 km/s with an error of about 0.80 km/s .

Tau1 Eridani 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 2.8200000 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, Age) of Tau1 Eridani

Tau1 Eridani has a spectral type of F5/F6V. This means the star is a blue to white main sequence dwarf star. The star is 7406.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24155.6572566400000000s. The star has a B-V Colour Index of 0.48 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,369 Kelvin.

Tau1 Eridani Radius has been calculated as being 1.37 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 953,253.95.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 1.39. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is 0.02 with an error value of 0.02 Fe/H with the Sun has a value of 1 to put it into context.

The stars age according to Hipparcos data files put the star at an age of about 3.00 Billion years old but could be between 2.30 and 3.60 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.

Tau1 Eridani Apparent and Absolute Magnitudes

Tau1 Eridani has an apparent magnitude of 4.47 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 3.74 If you used the 2007 Parallax value, you would get an absolute magnitude of 3.71. 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 Tau1 Eridani

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 71.56 which gave the calculated distance to Tau1 Eridani as 45.58 light years away from Earth or 13.97 parsecs. It would take a spaceship travelling at the speed of light, 45.58 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 70.32 which put Tau1 Eridani at a distance of 46.38 light years or 14.22 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 7,406.00 Parsecs or 24,155.66 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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Tau1 Eridani Facts

Visual Facts

Alternative NamesHD 17206, HIP 12843, HR 818, 22 G. Eridani, 1 Eridani, 1 Eri, BD-19 518, Gliese 111
Star Type main sequence Dwarf Star
GalaxyMilky Way
Age3.00 Billion Years Old
Age Range2.30 - 3.60 Billion Years Old
Absolute Magnitude3.74 / 3.71
Visual / Apparent Magnitude4.47
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)02h 45m 05.98
Declination (Dec.)-18° 34` 21.5
Galactic Latitude-62.53 degrees
Galactic Longitude200.83 degrees
1997 Distance from Earth71.56 Parallax (milliarcseconds)
 45.58 Light Years
 13.97 Parsecs
2007 Revised Distance from Earth70.32 Parallax (milliarcseconds)
 46.38 Light Years
 14.22 Parsecs
Galacto-Centric Distance24,155.66 Light Years / 7,406.00 Parsecs
Proper Motion Dec.37.19 ± 1.36 milliarcseconds/year
Proper Motion RA.334.20 ± 1.83 milliarcseconds/year
B-V Index0.48
Radial Velocity25.90 ± 0.80 km/s
Iron Abundance0.02 ± 0.02 Fe/H
Semi-Major Axis7245.00
Stellar Luminosity (Lsun)2.82
Spectral TypeF5/F6V
Associated / Clustered StarsTau3 Eridani
Tau4 Eridani
Tau5 Eridani
Tau6 Eridani
Tau7 Eridani
Tau8 Eridani
Tau9 Eridani
Colour(F) blue to white

Estimated Facts

Calculated Effective Temperature6,369 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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