When is the best time to observe Regulus?

Regulus is best observed from January through March, with peak visibility during February when it transits around midnight in the Northern Hemisphere.

Where is Regulus located in the sky?

Regulus lies in the constellation Leo at right ascension 10h 08m and declination +11° 58′.

What telescope do I need to split Regulus?

Splitting Regulus requires an aperture of roughly 60 mm or larger — the components are separated by about 175.9″ at magnitudes near 1.4. The companion is about 6.9 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Regulus — Double Star in Leo

HIP 49669; Alpha Leonis; 32 Leonis

Magnitude 1.4^m DoubleStar Leo Visible

Star Map + List + Plan

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

Magnitude 1.35

Spectral Type B8IVn supergiant

Star Color Blue-white (B-V -0.11)

Temperature 12433 K

Radius 3.1 R☉

Distance 79 ly

2Position & Identifiers

RA 10h 08m 22.3s

Dec +11° 58' 02.0"

Constellation Leo

HR 3982

HIP 49669

HD 87901

SAO 98967

Bayer Alpha

Flamsteed 32 Leo

Double Cat 7654

SIMBAD Wikipedia

3How easy to split?

Primary 1.4 mag Companion 8.2 mag Separation 175.9″

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

Easy Medium Hard Very hard Impossible

Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs

4Visibility

Set a location in User Settings to see visibility data.

Best season Jan – Mar (peak: Feb)

5Multiple Star System Quadruple D: optical

Components 4 (quadruple)

Component IDs AB

Separation 175.9″

Companion Mag 8.2

Position Angle 308°

Star Colors A: Blue-white

Discoverer STFB 6

Notes

AB binary, B, 8.13V, +0.86(B-V), +0.51(U-B), K1V. BC, 7.6, 13.1v, 2000y, a = 4.163".

Separation over time

Measured 1779 → 2023 (244 y)

Separation drift 168.3" → 175.9" (+7.60")

Rate +0.0311" / y

PA drift 307° → 308° (+1°, +0.004°/y)

Apparent motion is significant on a human timescale — worth revisiting in a decade.

Measured from the WDS observational archive. No orbital solution has been derived — most likely the period is too long to fit an orbit to the available measurement arc.