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Aldebaran, Alpha Tauri, 87 Tauri, HD29139, HIP21421, HR1457

Aldebaran (Alpha Tauri) is a orange to red giant star that can be located in the constellation of Taurus. Aldebaran is the 14th brightest star in the night sky and is the brightest star in Taurus based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it. It is calculated at being 6.600 Billion Years old. This information comes from ExoPlanet. Aldebaran has at least 1 Extrasolar Planets believed to be in orbit around the star.

Aldebaran is the brightest star in the constellation hence its Alpha Tauri status. It is probably mistaken by some to be the location of Alderaan, the planet in the Star Wars franchise because their name start the same.

Aldebaran is the biggest star that has a possible planet in orbit round it on this site. Other large stars with planets include Pollux and Hamal but this star is larger than both. The planet would be a gas planet and would be many times the size of Jupiter. If we had Aldebaran instead of the Sun as our star, it would reach out to halfway between the Sun and Mercury. Our planet would be less likely to have life because it`d be too hot. Ref: Illionois University

Aldebaran's Alternative Names

Alpha Tauri is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR1457. HIP21421 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD29139. The Gliese ID of the star is GL 171.1A. 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.

Aldebaran has alternative name(s) :- Alpha Tau . In Arabic, it is known as Ad-Dabaran.

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 87 Tauri with it shortened to 87 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+16 629.

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

Location of Aldebaran

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 Aldebaran, the location is 04h 35m 55.20 and +16° 30` 35.1 .

Proper Motion of Aldebaran

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 -188.94 ± 0.43 miliarcseconds/year towards the north and 63.45 ± 0.77 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 54.26000 km/s with an error of about 0.03 km/s .

Aldebaran 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 502.13 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, Mass) of Aldebaran

Aldebaran has a spectral type of K5III. This means the star is a orange to red giant star. The star is 7,419.00 Parsecs from the Galactic Centre or terms of Light Years is 24,198.06 s. The star has a B-V Colour Index of 1.53 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,933 Kelvin.

Aldebaran Radius has been calculated as being 26.88 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 18,704,500.82.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 27.51. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's solar mass is 1.13 times that of the Sun's. The Sun's Mass is 1,989,100,000,000,000,000,000 billion kg. which to calculate using this website is too large. To give idea of size, the Sun is 99.86% the mass of the solar system.

The star's metallicity is -0.270000, this value is the fractional amount of the star that is not Hydrogen (X) or Helium (Y). An older star would have a high metallicity whereas a new star would have a lower one.

The star is believed to be about 6.60 Billion years old. To put in context, the Sun is believed to be about five billion years old and the Universe is about 13.8 billion years old.

Aldebaran Apparent and Absolute Magnitudes

Aldebaran has an apparent magnitude of 0.87 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 -0.63 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.68. 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 Aldebaran

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 50.09 which gave the calculated distance to Aldebaran as 65.12 light years away from Earth or 19.96 parsecs. It would take a spaceship travelling at the speed of light, 65.12 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 48.94 which put Aldebaran at a distance of 66.65 light years or 20.43 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 7,419.00 Parsecs or 24,198.06 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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Aldebaran Facts

Visual Facts


 Aldebaran
Alternative NamesAlpha Tauri, Alpha Tau, Ad-Dabaran, HD 29139, HIP 21421, HR 1457, 87 Tauri, 87 Tau, BD+16 629, Gliese 171.1A
Spectral TypeK5III
Multiple Star SystemYes
Star TypeGiant Star
Colour orange to red
GalaxyMilky Way
ConstellationTaurus
Age6.60 Billion Years Old
Absolute Magnitude-0.63 / -0.68
Visual / Apparent Magnitude0.87
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)04h 35m 55.20
Declination (Dec.)+16° 30` 35.1
Galactic Latitude-20.25 degrees
Galactic Longitude180.97 degrees
1997 Distance from Earth50.09 Parallax (milliarcseconds)
 65.12 Light Years
 19.96 Parsecs
2007 Distance from Earth48.94 Parallax (milliarcseconds)
 66.65 Light Years
 20.43 Parsecs
Galacto-Centric Distance24,198.06 Light Years / 7,419.00 Parsecs
Proper Motion Dec.-188.94 ± 0.43 milliarcseconds/year
Proper Motion RA.63.45 ± 0.77 milliarcseconds/year
B-V Index1.53
Radial Velocity54.26 ± 0.03 km/s
Iron Abundance-0.17 ± 9.99 Fe/H
Eccentricity0.16
Semi-Major Axis7280.00
Stellar Luminosity (Lsun)502.13
Brightest in Night Sky14th

Companions (Multi-Star and Exoplanets) Facts


Exoplanet Count1

Estimated Facts


Calculated Effective Temperature3,933 Kelvin
Mass Compared to the Sun1.13

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
29139+16 629.0A1.1000065.00000-189.00000K5Orange
B13.600001877
C11.300001923
CD13.700001923
E1899
F13.600001908

Location of Aldebaran in Taurus


Aldebaran (Alpha Tauri) Location in Taurus

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


List of Extrasolar Planets orbiting Aldebaran


NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastronInclination
Aldebaran bConfirmed0.53628.9600.119981.46287.0001998.000

Related Stars

Aldebaran Solar System


This is a N.A.S.A. impression of what the solar system might look like. If the star is not on display, its because its so small compared to the orbits of the outer planets. The green area denotes the habital zone which if the planet is within that area, life could exist. The habital zone might not appear on the picture because its outside the area for the picture. Our planets show the orbit of the planet if its was in our solar system. For more information about the planet and other exoplanetary stuff, visit N.A.S.A.

Aldebaran Solar System

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