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Aldebaran (Alpha Tauri) - HD29139 - HIP21421 - HR1457

Aldebaran (Alpha Tauri) is a orange to red giant star that can be located in the constellation of Taurus. It is the 15th brightest star in the night sky. It is calculated at being 7.000 Billion Years old. This information comes from ExoPlanet. 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. Aldebaran has alternative name(s), Alpha Tau,87 Tauri , 87 Tau. In Arabic, it is known as Ad-Dabaran. 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

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 +16d30`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.

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 32.0000000 that I have given is based on the Spectral Types page that I have found on the Internet. You might find a different figure, one that may have been calculated rather than generalised that I have done. The figure is always the amount times the luminosity of the Sun. It is an imprecise figure because of a number of factors including but not limited to whether the star is a variable star and distance.

Physical Properties (Colour, Temperature, Age, Mass, Radius) of Aldebaran

Aldebaran has a spectral type of K5III. This means the star is a orange to red giant star. 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 has been calculated as 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. The star's solar mass is 1.00 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 7.00 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.

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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Aldebaran Facts

Alternative Names

Traditional/Proper NameAldebaran
Short Name87 Tau
Arabic NameAd-Dabaran
English Meaning'Follower' of the Pleiades
Bayer DesignationAlpha Tauri
Alternative Name(s)Alpha Tau,87 Tauri
Hipparcos Library I.D.21421
Yale Bright Star Catalogue (HR) Id1457
Bonner DurchmusterungBD+16 629
Henry Draper Designation29139

Visual Facts

Star Typegiant star
Age7.000 Billions of Years
Absolute Magnitude-0.63 / -0.68
Apparent Magnitude0.87
Right Ascension (R.A.)04h 35m 55.20
Declination (Dec.)+16d30`35.1
1997 Distance from Earth50.09 Parallax (milliarcseconds)
 65.12 Light Years
 19.96 Parsecs
2007 Revised Distance from Earth48.94 Parallax (milliarcseconds)
 66.65 Light Years
 20.43 Parsecs
Proper Motion Dec.-188.94 ± 0.43 milliarcseconds/year
Proper Motion RA.63.45 ± 0.77 milliarcseconds/year
B-V Index1.53
Spectral TypeK5III
Brightest in Night Sky15th
Colour(K) Orange to Red

Companions (Multi-Star and Exoplanets) Facts

Exoplanet Count1

Estimated Facts

Radius (x the Sun)26.88
Luminosity (x the Sun)32.0000000
Calculated Effective Temperature3,933 Kelvin
Mass Compared to the Sun1.00
Metallicity-0.27000

Sources and Links

SIMBAD SourceLink

Related Stars

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 AxisPeriastron
Aldebaran BConfirmed6.47628.9600.119981.46287.000

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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