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Sigma Leonis, 77 Leonis, HD98664, HIP55434

Sigma Leonis is a blue main sequence dwarf star that can be located in the constellation of Leo. Sigma 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.

Sigma Leonis is the Bayer Classification for the star. HIP55434 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD98664. The Id of the star in the Gould Star Catalogue is 46. 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 Sigma 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 Sigma Leonis, the location is 11h 21m 08.25 and +06d01`45.7 .

Proper Motion of Sigma 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 -11.48 ± 0.16 miliarcseconds/year towards the north and -92.97 ± 0.24 miliarcseconds/year east if we saw them in the horizon.

Sigma Leonis 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 42.0000000 that I have given is based on the Spectral Types page that I have found on the Internet. You might find a different figure, one that may have been calculated rather than generalised that I have done. The figure is always the amount times the luminosity of the Sun. It is an imprecise figure because of a number of factors including but not limited to whether the star is a variable star and distance.

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

Sigma Leonis has a spectral type of B9.5Vs. This means the star is a blue main sequence dwarf star. The star is 7410.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24168.7037904000000000s. The star has a B-V Colour Index of -0.05 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 10,395 Kelvin.

Sigma Leonis Radius has been calculated as being 2.93 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,040,512.39.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 3.01. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Sigma Leonis Apparent and Absolute Magnitudes

Sigma Leonis has an apparent magnitude of 4.05 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 -0.04 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.10. 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 Sigma Leonis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 15.24 which gave the calculated distance to Sigma Leonis as 214.02 light years away from Earth or 65.62 parsecs. It would take a spaceship travelling at the speed of light, 214.02 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 14.82 which put Sigma Leonis at a distance of 220.08 light years or 67.48 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 7,410.00 Parsecs or 24,168.70 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Meteor Showers Radiating from near Sigma Leonis

The Sigma Leonids Meteor Shower radiants from a point near this star. The meteor shower runs typically between 9-Feb - 13 Mar with a peak date of Feb 25 - 26. The speed of a meteor in the shower is 23 Km/s.

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.

Sigma Leonis Facts

Alternative Names

Flamsteed Name77 Leonis
Flamsteed Short Name77 Leo
Bayer DesignationSigma Leonis
Hipparcos Library I.D.55434
Bonner DurchmusterungBD+06 2437
Gould I.D.46
Henry Draper Designation98664

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude-0.04 / -0.10
Visual / Apparent Magnitude4.05
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)11h 21m 08.25
Declination (Dec.)+06d01`45.7
Galactic Latitude59.90 degrees
Galactic Longitude253.36 degrees
1997 Distance from Earth15.24 Parallax (milliarcseconds)
 214.02 Light Years
 65.62 Parsecs
2007 Revised Distance from Earth14.82 Parallax (milliarcseconds)
 220.08 Light Years
 67.48 Parsecs
Galacto-Centric Distance24,168.70 Light Years / 7,410.00 Parsecs
Proper Motion Dec.-11.48 ± 0.16 milliarcseconds/year
Proper Motion RA.-92.97 ± 0.24 milliarcseconds/year
B-V Index-0.05
Radial Velocity-5.30 ± 2.70 km/s
Spectral TypeB9.5Vs
Colour(B) blue

Estimated Facts

Luminosity (x the Sun)42.0000000
Calculated Effective Temperature10,395 Kelvin

Sources and Links

SIMBAD SourceLink

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