Universe Guide


Regulus (Alpha Leonis) - HD87901 - HIP49669 - HR3982

Regulus (Alpha Leonis) is a blue main sequence dwarf star that can be located in the constellation of Leo. It is the 22nd brightest star in the night sky. Alpha Leonis is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR3982. HIP49669 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD87901. Regulus has alternative name(s), 32 Leonis , 32 Leo.

Regulus is the brightest star in the constellation hence its Flamsteed classification of "Alpha Leonis". It is not actually one but a multiple star system consisting of two pairs of two stars. The brightest is a Blue-white star and is much bigger than our own the sun.

What may surprise you to know is that this star is more oval or egg-shaped than other stars. Reasons for this is because it spins faster than other stars, for example, our own star, The Sun rotates at about 4,500 miles an hour whereas Regulus rotates at about 700,000 miles an hour. Its also five times as big as the Sun. In addition to the rotation speed, it could be the fact that it is a multi-star system where the other stars pull as they orbit causing the bulge. All stars including our own bulge a little affected by the gravity of the orbiting planets.

Location of Regulus

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 Regulus, the location is 10h 08m 22.46 and +11d58`01.9 .

Proper Motion of Regulus

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 005.59 ± 000.21 towards the north and -248.73 ± 000.35 east if we saw them in the horizon.

Regulus 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 140.0000000 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 Regulus

Regulus has a spectral type of B7V. This means the star is a blue coloured main sequence dwarf star. The star has a B-V Colour Index of -0.08 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 11,099 Kelvin.

Regulus has been calculated as 3.09 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,151,413.60.km.

The star has companion stars which are in orbit close by, it has at least the following companions in close orbit, Regulus B, Regulus C.

Regulus Apparent and Absolute Magnitudes

Regulus has an apparent magnitude of 1.36 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 -0.52 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 Regulus

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 42.09 which gave the calculated distance to Regulus as 77.49 light years away from Earth or 23.76 parsecs. In 2007, Hipparcos data was revised with a new parallax of 41.13 which put Regulus at a distance of 79.30 light years or 24.31 parsecs.

It would take a spaceship travelling at the speed of light, 77.49 years using the 1997 distance to get there. We don't have the technology or spaceship that can carry people over that distance yet.

Meteor Showers Radiating from near Regulus

The Alpha Leonids Meteor Shower radiants from a point near this star. The meteor shower runs typically between 13-Jan - 13-Feb with a peak date of 24/31 Jan.

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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

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Regulus Facts

Alternative Names

Traditional NameRegulus
Short Name32 Leo
Bayer DesignationAlpha Leonis
Alternative Name(s)32 Leonis
Hipparcos Library I.D.49669
Yale Bright Star Catalogue (HR) Id3982
Bonner DurchmusterungBD+12 2149
Henry Draper Designation87901

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude-0.52 / -0.57
Apparent Magnitude1.36
Right Ascension (R.A.)10h 08m 22.46
Declination (Dec.)+11d58`01.9
1997 Distance from Earth42.09 Parallax (milliarcseconds)
 77.49 Light Years
 23.76 Parsecs
2007 Distance from Earth41.13 Parallax (milliarcseconds)
 79.30 Light Years
 24.31 Parsecs
Proper Motion Dec.5.59 ± 0.21 milliarcseconds/year
Proper Motion RA.-248.73 ± 0.35 milliarcseconds/year
B-V Index-0.08
Spectral TypeB7V
Brightest in Night Sky22nd
Colour(B) blue

Companions (Multi-Star and Exoplanets) Facts

Companion StarsRegulus B
Regulus C

Estimated Facts

Radius (x the Sun)3.09
Luminosity (x the Sun)140.0000000
Calculated Effective Temperature11,099 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
87901+12 2149.0A1.30000-248.000003.00000B8Blue/White
87884+12 2147.0B7.60000-225.000006.00000GYellow1836

Location of Regulus in Leo

Regulus (Alpha Leonis) Location in Leo

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

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