Epsilon Leonis (Algenubi)
Epsilon Leonis (Algenubi) is a star in the constellation Leo, magnitude 3.0.
The southern star of the Lion’s head — more powerful than Regulus, though it looks far fainter.
Its names are directions. Algenubi and Ras Elased Australis both mean ‘the southern star of the lion’s head’: Genubi is Arabic for ‘south’, Australis is Latin.
Looks deceive here. Epsilon Leonis appears much fainter than Regulus, but only because it lies more than three times as far away. Its absolute magnitude — how bright it would look from a standard distance — is −1.49, well ahead of Regulus. It is a yellow giant of about four solar masses that has finished burning hydrogen in its core and swollen to 21 times the Sun’s radius, shining 282 times as brightly.
Epsilon Leonis (Algenubi) is 250 light-years away: the light we see from it set off around 1775, around the time William Herschel discovered Uranus.
Did you know?
- Half the Sun’s metals. Its atmosphere holds only about half the Sun’s share of elements heavier than hydrogen and helium — a sign that it formed from less-enriched gas.
- A slow spinner. Seen from Earth, its surface turns at only about 8 kilometres a second. Stars tend to slow down as they swell into giants.
The yellowish 3rd-magnitude star at the tip of the Sickle, the backwards question mark that forms the Lion’s head, with Regulus at its base. Compare its pale yellow with blue-white Regulus.
When and where to see it
It is best placed in the evening sky around March, when it crosses the meridian at about 10 pm local time (around midnight in February). It can be seen from everywhere north of 66°S and never sets north of 66°N.
At its highest it stands 64° up from 50°N, 79° up from 35°N, 66° up from the equator, 31° up from 35°S.
Facts
- Type
- Star
- Constellation
- Leo
- Designations
- Algenubi, ε Leo, 17 Leo, HR 3873, HD 84441, HIP 47908
- Magnitude
- 3.0
- Position
- RA 9h 45.9m, Dec +23° 46′ (J2000)
- Spectral type
- G1IIIa
- Colour
- yellow (B−V 0.81)
- Distance
- 250 light-years
- Discovered
- Known since antiquity
Open AstroPilot to see when Epsilon Leonis (Algenubi) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.