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45 Eridani, HD28749, HIP21139, HR1437

45 Eridani is a orange to red giant 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.

45 Eridani's Alternative Names

The Id of the star in the Yale Bright Star Catalogue is HR1437. HIP21139 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD28749.

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 45 Eridani with it shortened to 45 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 231 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-00 713.

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

Location of 45 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 45 Eridani, the location is 04h 31m 52.67 and -00° 02` 38.4 .

Proper Motion of 45 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 -8.19 ± 0.22 miliarcseconds/year towards the north and -1.85 ± 0.38 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 16.30000 km/s with an error of about 0.80 km/s .

45 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 762.1100000 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 45 Eridani

45 Eridani has a spectral type of K3II-III. This means the star is a orange to red giant star. The star is 7567.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24680.7802404800000000s. The star has a B-V Colour Index of 1.32 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,289 Kelvin.

45 Eridani Radius has been calculated as being 44.90 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 31,238,958.84.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 35.50. 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 -0.08 with an error value of 0.06 Fe/H with the Sun has a value of 1 to put it into context.

45 Eridani Apparent and Absolute Magnitudes

45 Eridani has an apparent magnitude of 4.91 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 -2.12 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.61. 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 45 Eridani

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.93 which gave the calculated distance to 45 Eridani as 829.93 light years away from Earth or 254.45 parsecs. It would take a spaceship travelling at the speed of light, 829.93 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 4.97 which put 45 Eridani at a distance of 656.26 light years or 201.21 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 7,567.00 Parsecs or 24,680.78 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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45 Eridani Facts

Visual Facts

Alternative NamesHD 28749, HIP 21139, HR 1437, 231 G. Eridani, 45 Eri, BD-00 713
Star TypeGiant Star
GalaxyMilky Way
Absolute Magnitude-2.12 / -1.61
Visual / Apparent Magnitude4.91
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)04h 31m 52.67
Declination (Dec.)-00° 02` 38.4
Galactic Latitude-30.63 degrees
Galactic Longitude195.34 degrees
1997 Distance from Earth3.93 Parallax (milliarcseconds)
 829.93 Light Years
 254.45 Parsecs
2007 Revised Distance from Earth4.97 Parallax (milliarcseconds)
 656.26 Light Years
 201.21 Parsecs
Galacto-Centric Distance24,680.78 Light Years / 7,567.00 Parsecs
Proper Motion Dec.-8.19 ± 0.22 milliarcseconds/year
Proper Motion RA.-1.85 ± 0.38 milliarcseconds/year
B-V Index1.32
Radial Velocity16.30 ± 0.80 km/s
Iron Abundance-0.08 ± 0.06 Fe/H
Semi-Major Axis8246.00
Stellar Luminosity (Lsun)762.11
Spectral TypeK3II-III
Colour(K) Orange to Red

Estimated Facts

Calculated Effective Temperature4,289 Kelvin

Sources and Links

SIMBAD SourceLink

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