Universe Guide

Alpha Doradus

Alpha Doradus Facts

  • Alpha Doradus is a rotating main sequence star that can be located in the constellation of Dorado. The description is based on the spectral class.
  • Alpha Doradus is a main star of the constellation outline.
  • Based on the spectral type (A0V:) of the star, the star's colour is blue - white .
  • Alpha Doradus is the 1st brightest star in Dorado 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.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 168.65 light years away from us. Distance

Alpha Doradus's Alternative Names

Alpha Doradus (Alf Dor) 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 HR1465. HIP21281 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD29305.

Alpha Doradus has alternative name(s) :- , alf Dor.

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

Location of Alpha Doradus

The location of the main sequence 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 Alpha Doradus, the location is 04h 33m 59.72 and -55° 02` 42.0 .

Radial Velocity and Proper Motion of Alpha Doradus

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 10.93 ± 0.31 milliarcseconds/year towards the north and 57.75 ± 0.31 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 25.60000 km/s with an error of about 0.74 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 Alpha Doradus

Alpha Doradus Colour and Temperature

Based on the star's spectral type of A0V: , Alpha Doradus's colour and type is blue - white main sequence star. The star has a B-V Colour Index of -0.07 which means the star's temperature is about 10,845 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

Alpha Doradus 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 171.40 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Alpha Doradus Radius

Alpha Doradus estimated radius has been calculated as being 3.12 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,172,362.27.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 2.9953456397227367379441290895. The figure is derived at by using the formula from SDSS rather than peer reviewed papers. It has been known to produce widely incorrect figures.

Alpha Doradus Apparent and Absolute Magnitudes

Alpha Doradus has an apparent magnitude of 3.30 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 -0.36 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.27. 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 Alpha Doradus

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 18.56000 which gave the calculated distance to Alpha Doradus as 175.73 light years away from Earth or 53.88 parsecs. If you want that in miles, it is about 1,033,050,836,829,555.79, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 19.34000 which put Alpha Doradus at a distance of 168.65 light years or 51.71 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 10,665,878.81 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 7,404.00 Parsecs or 24,149.13 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 Alpha Doradus

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)
Airbus A380736153,667,791.41
Speed of Sound (Mach 1)767.269147,405,270.49
Concorde (Mach 2)1,534.5473,702,539.18
New Horizons Probe33,0003,427,257.41
Speed of Light670,616,629.00168.65

Variable Type of Alpha Doradus

The star is a rotating Alpha2 Canum Venatic variable type which means that its size changes over time. The Variable Type is usually named after the first star of that type to be spotted. Alpha Doradus brightness ranges from a magnitude of 3.243 to a magnitude of 3.204 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 2.9 days (variability).

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 Alpha Doradus Facts and Figures

Visual Facts

Primary / Proper / Traditional NameAlpha Doradus
Alternative NamesAlf Dor, HD 29305, HIP 21281, HR 1465, alf Dor
Spectral TypeA0V:
Constellation's Main StarYes
Multiple Star SystemYes
Star Type Main Sequence Dwarf Star
GalaxyMilky Way
Absolute Magnitude -0.36 / -0.27
Visual / Apparent Magnitude3.30
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)04h 33m 59.72
Declination (Dec.)-55° 02` 42.0
Galactic Latitude-41.41551486 degrees
Galactic Longitude263.83262609 degrees
1997 Distance from Earth18.56000 Parallax (milliarcseconds)
 175.73 Light Years
 53.88 Parsecs
2007 Distance from Earth19.34000 Parallax (milliarcseconds)
 168.65 Light Years
 51.71 Parsecs
  10,665,878.81 Astronomical Units
Galacto-Centric Distance24,149.13 Light Years / 7,404.00 Parsecs
Proper Motion Dec.10.93000 ± 0.31000 milliarcseconds/year
Proper Motion RA.57.75000 ± 0.31000 milliarcseconds/year
B-V Index-0.07
Radial Velocity25.60000 ± 0.74 km/s
Semi-Major Axis6589.0000000
Stellar Luminosity (Lsun)171.4000000

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassRotating
Variable Star TypeAlpha2 Canum Venatic
Mean Variability Period in Days2.943
Variable Magnitude Range (Brighter - Dimmer)3.204 - 3.243

Estimated Calculated Facts

Radius (x the Sun)3.00
Effective Temperature10,845 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
-55 664.4C10.0000024.00000120.000001938
29305-55 663.4A4.1000052.000001.00000A0White

Location of Alpha Doradus in Dorado

Alpha Doradus Location in Dorado

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

Dorado Main Stars

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