Universe Guide


Upsilon Leonis, 91 Leonis, HD100920, HIP56647

Upsilon Leonis is a white to yellow giant star that can be located in the constellation of Leo. Upsilon Leonis 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.

Upsilon Leonis is the Bayer Classification for the star. HIP56647 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD100920. The Id of the star in the Gould Star Catalogue is 69. Stars in the southern hemisphere are more likely to have a Gould Id than the northern hemisphere. For example, there are no Gould classified stars in Ursa Major.

Location of Upsilon Leonis

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 Upsilon Leonis, the location is 11h 36m 56.93 and -00d49`25.9 .

Proper Motion of Upsilon Leonis

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 43.37 ± 0.15 miliarcseconds/year towards the north and 1.76 ± 0.22 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Upsilon Leonis

Upsilon Leonis has a spectral type of G9III. This means the star is a white to yellow giant star. The star is 7402.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24142.6107228800000000s. The star has a B-V Colour Index of 0.98 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,888 Kelvin.

Upsilon Leonis Radius has been calculated as being 9.83 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 6,840,997.74.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 10.01. 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 -0.18 with an error value of 0.03 Fe/H with the Sun has a value of 1 to put it into context.

Upsilon Leonis Apparent and Absolute Magnitudes

Upsilon Leonis has an apparent magnitude of 4.30 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 0.61 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.57. 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 Upsilon Leonis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 18.31 which gave the calculated distance to Upsilon Leonis as 178.13 light years away from Earth or 54.61 parsecs. It would take a spaceship travelling at the speed of light, 178.13 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 17.97 which put Upsilon Leonis at a distance of 181.50 light years or 55.65 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 7,402.00 Parsecs or 24,142.61 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.

Upsilon Leonis Facts

Alternative Names

Flamsteed Name91 Leonis
Flamsteed Short Name91 Leo
Bayer DesignationUpsilon Leonis
Hipparcos Library I.D.56647
Bonner DurchmusterungBD-00 2458
Gould I.D.69
Henry Draper Designation100920

Visual Facts

Star Typegiant star
Absolute Magnitude0.61 / 0.57
Visual / Apparent Magnitude4.30
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)11h 36m 56.93
Declination (Dec.)-00d49`25.9
Galactic Latitude56.80 degrees
Galactic Longitude267.26 degrees
1997 Distance from Earth18.31 Parallax (milliarcseconds)
 178.13 Light Years
 54.61 Parsecs
2007 Revised Distance from Earth17.97 Parallax (milliarcseconds)
 181.50 Light Years
 55.65 Parsecs
Galacto-Centric Distance24,142.61 Light Years / 7,402.00 Parsecs
Proper Motion Dec.43.37 ± 0.15 milliarcseconds/year
Proper Motion RA.1.76 ± 0.22 milliarcseconds/year
B-V Index0.98
Radial Velocity1.70 ± 0.60 km/s
Iron Abundance-0.18 ± 0.03 Fe/H
Spectral TypeG9III
Colour(G) White to Yellow

Estimated Facts

Calculated Effective Temperature4,888 Kelvin

Sources and Links

SIMBAD SourceLink

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