Lambda Leonis (λ Leonis, abbreviated Lam Leo, λ Leo), formally named Alterf , is a

star A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make ...

in the constellation of

Leo Leo or Léo may refer to: Acronyms * Law enforcement officer * Law enforcement organisation * ''Louisville Eccentric Observer'', a free weekly newspaper in Louisville, Kentucky * Michigan Department of Labor and Economic Opportunity Arts an ...

. The star is bright enough to be seen with the naked eye, having an apparent visual magnitude of 4.32 Based upon an annual parallax shift of 0.00991

arcsecond A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

s, it is located about 329

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 101 ...

s from the Sun. At that distance, the visual magnitude of the star is reduced by an interstellar absorption factor of 0.06 because of

extinction Extinction is the termination of a kind of organism or of a group of kinds ( taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed ...

Nomenclature

''λ Leonis'' ( Latinised to ''Lambda Leonis'') is the star's Bayer designation. It bore the traditional name ''Alterf'', from the

Arabic Arabic (, ' ; , ' or ) is a Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C. E.Watson; Walte ...

الطرف ''aṭ-ṭarf'' "the view (of the lion)". In 2016, the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

(IAU) organized a

Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize List of proper names of stars, proper names for stars for the international astronomical community. It operates under ...

(WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name ''Alterf'' for this star on February 1, 2017 and it is now so included in the List of IAU-approved Star Names. This star, along with

Xi Cancri Xi Cancri (ξ Cancri, abbreviated Xi Cnc, ξ Cnc) is a spectroscopic binary star system in the zodiac constellation of Cancer. It is visible to the naked eye with an apparent visual magnitude of +5.15. Based upon parallax measurements obt ...

, were the Persian ''Nahn'', "the Nose", and the Coptic ''Piautos'', "the Eye", both lunar asterisms.

Properties

This is a K-type giant star with a stellar classification of K4.5 III. It is a suspected variable star with a reported magnitude range of 4.28−4.34. The

interferometry Interferometry is a technique which uses the '' interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber o ...

-measured angular diameter of this star, after correcting for limb darkening, is , which, at its estimated distance, equates to a physical radius of nearly 45 times the

radius of the Sun Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3: :1\,R_ = 6.9 ...

. It shines with around 472 times the luminosity of the Sun, from an outer atmosphere that has an

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

of 3,900 K.

References

{{DEFAULTSORT:Lambda Leonis K-type giants Leo (constellation) Alterf Leonis, Lambda Leonis, 04 046750 Suspected variables 082308 3773 Durchmusterung objects