About Regulus
Description
Regulus is the brightest star in Leo at magnitude 1.35, a blue-white main-sequence star of spectral type B7V located about 79 light-years from Earth. It is actually a quadruple star system. Regulus spins extremely rapidly — at about 96% of its breakup velocity — completing a rotation in just 15.9 hours and making it severely oblate. Its luminosity is about 288 times solar.
Observing Tips
Regulus sits at the base of the Sickle of Leo — the reversed question-mark asterism forming the Lion's head and mane. It is the brightest star on the ecliptic, so it is frequently occulted by the Moon and occasionally by planets. The wide companion Regulus B/C (magnitude 8.1) is visible in a small telescope about 177 arcseconds away. Best observed February through June.
History
The name Regulus means 'little king' in Latin, given by Copernicus. It was one of the four Royal Stars of ancient Persia (along with Aldebaran, Antares, and Fomalhaut), marking the summer solstice around 3000 BC. The Babylonians called it 'the star that stands in the breast of the Lion.' Its position on the ecliptic has made it astronomically important since antiquity.
Fun Facts
Regulus rotates so fast that it is about 32% wider at the equator than at the poles. Its equatorial surface temperature is about 10,000 K while the poles reach 15,400 K due to gravity darkening. If it spun just 16% faster, it would tear itself apart.
Observe
1Physical Properties
2How easy to split?
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | Easy | Easy | Easy |
| 150 mm Newton 150mm Newt. | Easy | Easy | Easy |
| Celestron C8 (203 mm SCT) C8 203mm | Easy | Easy | Easy |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
3Visibility
Set a location in User Settings to see visibility data.
4Multiple Star System D: optical
Eyepiece View
A: 1.4 · B: 8.2 · Sep: 175.9″ · PA: 308° · N up, E left
Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 2.3″
Explore
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Size Comparison
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Compare Stars
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Stellar Lifecycle
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Spectral Classification
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Hertzsprung-Russell Diagram
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Blackbody Spectrum
12
Stellar Absorption Spectrum
Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.
13
Stellar Fusion
Discover
14Stellar Notes
15
Light Travel Time Machine
16
Relativistic Travel
Survey Image
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Nearby in the Sky
Other targets within a few degrees — pan your scope a little and keep exploring.
