Universe Guide

Regulus (Alpha Leonis, 32 Leonis) Star Facts

Regulus Facts

  • Regulus is a main sequence star that can be located in the constellation of Leo. The description is based on the spectral class.
  • Regulus is a main star of the constellation outline.
  • Based on the spectral type (B7V) of the star, the star's colour is blue .
  • Regulus is the 21st brightest star in the night sky and 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.
  • Regulus has a radius that is 3.09 times bigger than the Suns. Radius
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 79.30 light years away from us. Distance

Information on Regulus

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.

Regulus's Alternative Names

Alpha Leonis (Alf Leo) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in 1603. The brightest star in the constellation is normally given the Alpha designation, there are exceptions such as Pollux which is Beta Geminorum.

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.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John named the stars in the constellation with a number and its latin name, this star's Flamsteed designation is 32 Leonis. The Flamsteed name can be shortened to 32 Leo.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD+12 2149.

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

Location of Regulus

The location of the main sequence 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 Regulus, the location is 10h 08m 22.46 and +11° 58` 01.9 .

Radial Velocity and Proper Motion of Regulus

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 5.59 ± 0.21 milliarcseconds/year towards the north and -248.73 ± 0.35 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 5.90000 km/s with an error of about 2.40 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.

Physical Properties of Regulus

Regulus Temperature and Colour

Based on the star's spectral type of B7V , Regulus's colour and type is blue main sequence star. The star's effective temperature is 12,460 Kelvin which is hotter than our own Sun's effective Temperature which is 5,777 Kelvin.

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 239.45 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Regulus Radius

Regulus Radius has been calculated as being 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. If you need the diameter of the star, you just need to multiple the radius by 2.

Regulus Mass

The Regulus's solar mass is 3.80 times that of our star, the Sun. The Sun's Mass is 1,989,100,000,000,000,000,000 billion kg. which to calculate using this website is too large. To give idea of size, the Sun is 99.86% the mass of the solar system.

Regulus Iron Abundance

Regulus Iron Abundance is 0.21 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context. The value comes from the Hipparcos Extended Catalog.

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 42.09000 which gave the calculated distance to Regulus as 77.49 light years away from Earth or 23.76 parsecs. If you want that in miles, it is about 455,534,680,167,997.94, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 41.13000 which put Regulus at a distance of 79.30 light years or 24.31 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 5,014,262.50 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 7,411.00 Parsecs or 24,171.97 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Travel Time to Regulus

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Airbus A38073672,255,297.12
Speed of Sound (Mach 1)767.26969,310,631.19
Concorde (Mach 2)1,534.5434,655,270.43
New Horizons Probe33,0001,611,512.08
Speed of Light670,616,629.0079.30

Meteor Showers Radiating from near Regulus

The alpha Leonid Complex Meteor Shower radiants from a point near this star. The speed of a meteor in the shower is 12 Km/s.

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.

The Northern alpha Leonids Meteor Shower radiants from a point near this star. The meteor shower runs typically between with a peak date of 9th March. The speed of a meteor in the shower is 11 Km/s.

The Southern alpha Leonids Meteor Shower radiants from a point near this star. The speed of a meteor in the shower is 12 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.

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Additional Regulus Facts and Figures

Visual Facts

Primary / Proper / Traditional NameRegulus
Alternative NamesAlpha Leonis, Alf Leo, HD 87901, HIP 49669, HR 3982, 32 Leonis, 32 Leo, BD+12 2149
Spectral TypeB7V
Constellation's Main StarYes
Multiple Star SystemYes
Star Type Main Sequence Dwarf Star
GalaxyMilky Way
Absolute Magnitude -0.52 / -0.57
Visual / Apparent Magnitude1.36
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)10h 08m 22.46
Declination (Dec.)+11° 58` 01.9
Galactic Latitude48.93473609 degrees
Galactic Longitude226.42779079 degrees
1997 Distance from Earth42.09000 Parallax (milliarcseconds)
 77.49 Light Years
 23.76 Parsecs
2007 Distance from Earth41.13000 Parallax (milliarcseconds)
 79.30 Light Years
 24.31 Parsecs
 5,014,262.50 Astronomical Units
Galacto-Centric Distance24,171.97 Light Years / 7,411.00 Parsecs
Proper Motion Dec.5.59000 ± 0.21000 milliarcseconds/year
Proper Motion RA.-248.73000 ± 0.35000 milliarcseconds/year
B-V Index-0.08
Radial Velocity5.90000 ± 2.40 km/s
Iron Abundance0.2100 ± 9.99 Fe/H
Semi-Major Axis8018.0000000
Stellar Luminosity (Lsun)239.4500000
Brightest in Night Sky21st
Associated / Clustered StarsRegulus B
Regulus C

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Estimated Calculated Facts

Radius (x the Sun)3.09
Effective Temperature11,099 Kelvin
Mass Compared to the Sun3.80

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 Location in Leo

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

Leo Main Stars

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