Universe Guide


Ras Elased Australis, Epsilon Leonis, 17 Leonis, HD84441, HIP47908

Ras Elased Australis (Epsilon Leonis) is a white to yellow luminous giant star that can be located in the constellation of Leo. Ras Elased Australis is the brightest star in Leo 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.

Epsilon Leonis is the Bayer Classification for the star. HIP47908 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD84441.

Ras Elased Australis has alternative name(s), Algenubi , .

Location of Ras Elased Australis

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 Ras Elased Australis, the location is 09h 45m 51.10 and +23d46`27.4 .

Proper Motion of Ras Elased Australis

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 -9.21 ± 0.10 miliarcseconds/year towards the north and -45.61 ± 0.15 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Ras Elased Australis

Ras Elased Australis has a spectral type of G0II. This means the star is a white to yellow luminous giant star. The star is 7445.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24282.8609608000000000s. The star has a B-V Colour Index of 0.8 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,422 Kelvin.

Ras Elased Australis Radius has been calculated as being 20.73 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 14,423,914.43.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 20.35. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is -0.09 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Ras Elased Australis Apparent and Absolute Magnitudes

Ras Elased Australis has an apparent magnitude of 2.97 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 -1.46 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.42. 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 Ras Elased Australis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 13.01 which gave the calculated distance to Ras Elased Australis as 250.70 light years away from Earth or 76.86 parsecs. It would take a spaceship travelling at the speed of light, 250.70 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 13.22 which put Ras Elased Australis at a distance of 246.72 light years or 75.64 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 7,445.00 Parsecs or 24,282.86 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.

Ras Elased Australis Facts

Alternative Names

Traditional/Proper NameRas Elased Australis
Flamsteed Name17 Leonis
Flamsteed Short Name17 Leo
Bayer DesignationEpsilon Leonis
Alternative Name(s)Algenubi
Hipparcos Library I.D.47908
Bonner DurchmusterungBD+24 2129
Henry Draper Designation84441

Visual Facts

Star Typeluminous giant star
Absolute Magnitude-1.46 / -1.42
Visual / Apparent Magnitude2.97
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)09h 45m 51.10
Declination (Dec.)+23d46`27.4
Galactic Latitude48.20 degrees
Galactic Longitude206.82 degrees
1997 Distance from Earth13.01 Parallax (milliarcseconds)
 250.70 Light Years
 76.86 Parsecs
2007 Revised Distance from Earth13.22 Parallax (milliarcseconds)
 246.72 Light Years
 75.64 Parsecs
Galacto-Centric Distance24,282.86 Light Years / 7,445.00 Parsecs
Proper Motion Dec.-9.21 ± 0.10 milliarcseconds/year
Proper Motion RA.-45.61 ± 0.15 milliarcseconds/year
B-V Index0.80
Radial Velocity4.48 ± 0.09 km/s
Iron Abundance-0.09 ± 9.99 Fe/H
Spectral TypeG0II
Colour(G) White to Yellow

Estimated Facts

Calculated Effective Temperature5,422 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Location of Ras Elased Australis in Leo

Ras Elased Australis (Epsilon Leonis) Location in Leo

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

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