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Aldebaran (Alpha Tauri, 87 Tauri) Star Facts

Aldebaran Facts

  • Aldebaran is a giant star that can be located in the constellation of Taurus. The description is based on the spectral class.
  • Aldebaran is a main star of the constellation outline.
  • Based on the spectral type (K5III) of the star, the star's colour is orange to red .
  • 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 has a radius that is 44.13 times bigger than the Suns. Radius
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 66.65 light years away from us. Distance

Information on Aldebaran

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 (Alf Tau) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in 1603. The brightest star in the constellation is normally given the Alpha designation, there are exceptions such as Pollux which is Beta Geminorum.

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. 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 named the stars in the constellation with a number and its latin name, this star's Flamsteed designation is 87 Tauri. The Flamsteed name can be 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 objects' alternative names can be found at Star Names .

Location of Aldebaran

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

Radial Velocity and Proper Motion of Aldebaran

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 -188.94 ± 0.43 milliarcseconds/year towards the north and 63.45 ± 0.77 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 54.26 km/s with an error of about 0.03 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.

Physical Properties of Aldebaran

Aldebaran Temperature and Colour

Based on the star's spectral type of K5III , Aldebaran's colour and type is orange to red giant star. The star's effective temperature is 3,900 Kelvin which is cooler than our own Sun's effective Temperature which is 5,777 Kelvin

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.

Aldebaran Radius

Aldebaran Radius has been calculated as being 44.13 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 30,705,654.00.km. If you need the diameter of the star, you just need to multiple the radius by 2.

Aldebaran Mass

The Aldebaran's solar mass is 1.16 times that of our star, the Sun. 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.

Aldebaran Metalicity

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.

Aldebaran Estimated Age

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. If you want that in miles, it is about 382,816,084,301,716.68, based on 1 Ly = 5,878,625,373,183.61 miles.

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.

Using the 2007 distance, the star is roughly 4,213,960.63 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 7,419.00 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*.

Travel Time to Aldebaran

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Walking411,174,149,580.71
Car120372,471,652.69
Airbus A38073660,729,073.81
Speed of Sound (Mach 1)767.26958,254,143.36
Concorde (Mach 2)1,534.5429,127,033.72
New Horizons Probe33,0001,354,442.37
Speed of Light670,616,629.0066.65

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 Aldebaran Facts and Figures

Visual Facts


Primary / Proper / Traditional NameAldebaran
Alternative NamesAlpha Tauri, Alf Tau, Alpha Tau, Ad-Dabaran, HD 29139, HIP 21421, HR 1457, 87 Tauri, 87 Tau, BD+16 629, Gliese 171.1A
Spectral TypeK5III
Constellation's Main StarYes
Multiple Star SystemYes
Star TypeGiant Star
ColourOrange 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
 4,213,960.63 Astronomical Units
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 Calculated Facts


Radius (x the Sun)44.13
Effective Temperature3,933 Kelvin
Mass Compared to the Sun1.16

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 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 bConfirmed0.53628.9600.119981.46287.000

Taurus Main 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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