Mu Leonis (μ Leonis, abbreviated Mu Leo, μ Leo), also named Rasalas , is a star in the constellation of Leo. The

apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's lig ...

of this star is 3.88, which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 0.02628

arc second 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 n ...

s as measured by the Hipparcos satellite, this system is from the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. In 2014, an exoplanet was discovered to be orbiting the star.

Nomenclature

''μ Leonis'' ( Latinised to ''Mu Leonis'') is the star's Bayer designation. It bore the traditional names ''Rasalas'' and ''Alshemali'', both abbreviations of ''Ras al Asad al Shamaliyy''. 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, outreac ...

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 proper names for stars for the international astronomical community. It operates under Division C – Education ...

(WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name ''Rasalas'' for this star on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.

Properties

Mu Leonis is an evolved K-type

giant star A giant star is a star with substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moore, New York: Oxford University Press ...

with a stellar classification of . The trailing notation indicates that, for a star of its type, it has stronger than normal absorption lines of

cyanogen Cyanogen is the chemical compound with the formula ( C N)2. It is a colorless and highly toxic gas with a pungent odor. The molecule is a pseudohalogen. Cyanogen molecules consist of two CN groups – analogous to diatomic halogen molecu ...

and

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...

in its

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors ...

. It has around 1.5 times the Sun's mass, but has expanded to around 14 times the Sun's radius. Mu Leonis shines with 63 times the luminosity of the Sun from an outer atmosphere that has an effective temperature of 4,436 K. It is around 3.35 billion years old.

Planetary system

In 2014 it was announced that Mu Leonis has a planetary companion that is at least 2.4 times as massive as Jupiter and orbits with a period of 358 days. This planet was detected by measuring radial velocity variations caused by gravitational displacement from the orbiting body.

References

External links

* {{DEFAULTSORT:Mu Leonis K-type giants CN stars Planetary systems with one confirmed planet Leo (constellation) Leonis, Mu Rasalas Leonis, 24 048455 3905 085503 Durchmusterung objects