Universe Guide

Elnath (Beta Tauri, 112 Tauri) Star Facts

Elnath Facts

Information on Elnath

Elnath or El Nath depending on how you like to spell it, is the closest major star to the anti-centre of the galaxy. If I was at the Galactic Centre and shone a really powerful laser at Earth and then continued onwards. El Nath would be the nearest major star to the laser line. There are closer stars but none as well known as El Nath.

Elnath is also part of the Aurigae constellation but for purposes of One Star to One Constellation, El Nath is associated with Taurus. Even when its being used in Auriga, its still known as Beta Tauri or Elnath.

Elnath's Alternative Names

Beta Tauri (Bet Tau) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in the early nineteenth century. The brightest star in the constellation is normally given the Alpha designation although there are exceptions such as Pollux which is Beta Geminorum.

The Id of the star in the Yale Bright Star Catalogue is HR1791. HIP25428 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD35497.

Elnath has alternative name(s) :- Gam Aur, Gamma Aurigae, Beta Tau, Alnath.

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 112 Tauri with it shortened to 112 Tau.

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+28 795.

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

Location of Elnath

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 Elnath, the location is 05h 26m 17.50 and +28° 36` 28.3 .

Radial Velocity and Proper Motion of Elnath

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 -173.58 ± 0.17 milliarcseconds/year towards the north and 22.76 ± 0.34 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 9.20 km/s with an error of about 2.50 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.

Elnath 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 682.41 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 Elnath

Elnath Colour and Temperature

Elnath has a spectral type of B7III. This means the star is a blue giant star. The star has a B-V Colour Index of -0.13 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 12,762 Kelvin.

Elnath Radius

Radius has been calculated as being 3.59 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,497,835.30.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 3.67. 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 0.20 with an error value of 0.04 Fe/H with the Sun has a value of 1 to put it into context.

Elnath Apparent and Absolute Magnitudes

Elnath has an apparent magnitude of 1.65 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 -1.37 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.42. 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 Elnath

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 24.89 which gave the calculated distance to Elnath as 131.04 light years away from Earth or 40.18 parsecs. It would take a spaceship travelling at the speed of light, 131.04 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 24.36 which put Elnath at a distance of 133.89 light years or 41.05 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 8,467,111.30 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 7,441.00 Parsecs or 24,269.81 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Meteor Showers Radiating from near Elnath

The Daytime Beta Taurids Meteor Shower radiants from a point near this star. The meteor shower runs typically between 5 Jun- 17 Jul with a peak date of 28-Jun. The speed of a meteor in the shower is 27 Km/s. The amount of meteors predicted to be seen per hour (Zenith Hourly Rate) is 27.

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 Elnath Facts and Figures

Visual Facts

Primary / Proper / Traditional NameElnath
Alternative NamesBeta Tauri, Bet Tau, Gam Aur, Gamma Aurigae, Beta Tau, Alnath, HD 35497, HIP 25428, HR 1791, 112 Tauri, 112 Tau, BD+28 795
Spectral TypeB7III
Constellation's Main StarYes
Multiple Star SystemYes
Star TypeGiant Star
GalaxyMilky Way
Absolute Magnitude -1.37 / -1.42
Visual / Apparent Magnitude1.65
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)05h 26m 17.50
Declination (Dec.)+28° 36` 28.3
Galactic Latitude-3.75 degrees
Galactic Longitude177.99 degrees
1997 Distance from Earth24.89 Parallax (milliarcseconds)
 131.04 Light Years
 40.18 Parsecs
2007 Distance from Earth24.36 Parallax (milliarcseconds)
 133.89 Light Years
 41.05 Parsecs
 8,467,111.30 Astronomical Units
Galacto-Centric Distance24,269.81 Light Years / 7,441.00 Parsecs
Proper Motion Dec.-173.58 ± 0.17 milliarcseconds/year
Proper Motion RA.22.76 ± 0.34 milliarcseconds/year
B-V Index-0.13
Radial Velocity9.20 ± 2.50 km/s
Iron Abundance0.20 ± 0.04 Fe/H
Semi-Major Axis6488.00
Stellar Luminosity (Lsun)682.41
Brightest in Night Sky27th

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Estimated Calculated Facts

Radius (x the Sun)3.67
Effective Temperature12,762 Kelvin

Sources and Links

SIMBAD SourceLink

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.

Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
35497+28 795.0A1.8000025.00000-175.00000B8Blue/White

Location of Elnath in Taurus

Elnath Location in Taurus

The map was generated using Night Vision, an awesome free application by Brian Simpson.

Taurus Main Stars

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