Universe Guide

Eta2 Doradus

Eta2 Doradus Facts

Eta2 Doradus's Alternative Names

Eta2 Doradus (Eta02 Dor) 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 HR2245. HIP29353 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD43455.

Eta2 Doradus has alternative name(s) :- , NSV 02873.

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

Location of Eta2 Doradus

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 Eta2 Doradus, the location is 06h 11m 15.02 and -65° 35` 22.9 .

Radial Velocity and Proper Motion of Eta2 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 118.59 ± 0.23 milliarcseconds/year towards the north and -22.83 ± 0.23 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 34.50 km/s with an error of about 0.80 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.

Eta2 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 1,278.91 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 Eta2 Doradus

Eta2 Doradus Colour and Temperature

Eta2 Doradus has a spectral type of M2.5III. This means the star is a red giant star. The star has a B-V Colour Index of 1.59 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,804 Kelvin.

Eta2 Doradus Radius

Radius has been calculated as being 44.10 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 30,684,717.48.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 42.11. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Eta2 Doradus Apparent and Absolute Magnitudes

Eta2 Doradus has an apparent magnitude of 5.01 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 -1.56 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.46. 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 Eta2 Doradus

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 4.86 which gave the calculated distance to Eta2 Doradus as 671.12 light years away from Earth or 205.76 parsecs. It would take a spaceship travelling at the speed of light, 671.12 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 5.09 which put Eta2 Doradus at a distance of 640.79 light years or 196.46 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 40,522,501.47 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 7,386.00 Parsecs or 24,090.42 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of Eta2 Doradus

The star is a eruptive Irregular 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. Eta2 Doradus brightness ranges from a magnitude of 5.117 to a magnitude of 5.033 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 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 Eta2 Doradus Facts and Figures

Visual Facts

Primary / Proper / Traditional NameEta2 Doradus
Alternative NamesEta02 Dor, HD 43455, HIP 29353, HR 2245, NSV 02873
Spectral TypeM2.5III
Constellation's Main StarNo
Multiple Star SystemYes
Star TypeGiant Star
GalaxyMilky Way
Absolute Magnitude -1.56 / -1.46
Visual / Apparent Magnitude5.01
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)06h 11m 15.02
Declination (Dec.)-65° 35` 22.9
Galactic Latitude-28.65 degrees
Galactic Longitude275.31 degrees
1997 Distance from Earth4.86 Parallax (milliarcseconds)
 671.12 Light Years
 205.76 Parsecs
2007 Distance from Earth5.09 Parallax (milliarcseconds)
 640.79 Light Years
 196.46 Parsecs
 40,522,501.47 Astronomical Units
Galacto-Centric Distance24,090.42 Light Years / 7,386.00 Parsecs
Proper Motion Dec.118.59 ± 0.23 milliarcseconds/year
Proper Motion RA.-22.83 ± 0.23 milliarcseconds/year
B-V Index1.59
Radial Velocity34.50 ± 0.80 km/s
Semi-Major Axis6996.00
Stellar Luminosity (Lsun)1,278.91
Associated / Clustered StarsEta1 Doradus

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassEruptive
Variable Star TypeIrregular
Mean Variability Period in Days0.063
Variable Magnitude Range (Brighter - Dimmer)5.033 - 5.117

Estimated Calculated Facts

Radius (x the Sun)42.11
Effective Temperature3,804 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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