Delta Leonis (δ Leonis, abbreviated Delta Leo, δ Leo), also named Zosma , is a

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

in the

zodiac The zodiac is a belt-shaped region of the sky that extends approximately 8° north or south (as measured in celestial latitude) of the ecliptic, the Sun path, apparent path of the Sun across the celestial sphere over the course of the year. ...

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

of Leo. Based upon

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...

measurements, it lies at a distance of about 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 ...

Properties

δ Leonis is a

main-sequence star In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hert ...

with a

stellar classification In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

of A4 V, meaning it is larger and hotter than the

. It is a fairly well-studied star, allowing relatively accurate measurements of its age and size. The radius of the star, as measured directly using an

interferometer 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 op ...

, is about 214% of the Sun's radius and it is emitting more than 15 times as much luminosity as the Sun. The energy is being emitted from the outer envelope with 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 ...

, giving it the white hue characteristic of an

A-type star An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 ...

. Having a larger mass than the Sun it will have a shorter lifespan, and in another 600 million years or so will swell into an orange or

red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or ...

star before decaying quietly into a

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes fro ...

. This star is rotating rapidly, with a

projected rotational velocity Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge ...

of 180 km s⁻¹. The inclination of the axis of rotation to the line of sight from the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

is estimated at 38.1°, which would mean the

azimuth An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north. Mathematicall ...

al velocity along the equator is about 280 km s⁻¹. This rotation is producing an equatorial bulge, giving the star a pronounced

oblate spheroid A spheroid, also known as an ellipsoid of revolution or rotational ellipsoid, is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters. A spheroid has circ ...

al shape. The polar radius is about 84% of the radius along the equator. Based upon the location and trajectory of this star through space, it may be a member of the Ursa Major Moving Group, a type of

stellar kinematics In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space. Stellar kinematics encompasses the measurement of stellar velocities in the Milky Way and its satellites as well as ...

group that share a common origin and motion through space. The age of this group is about 500 million years.

Nomenclature

''δ Leonis'' ( Latinised to ''Delta Leonis'') is the star's

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. ...

. It bore the traditional names ''Zosma'' or ''Zozma'' and ''Duhr'' (rare spellings included ''Zozca'', ''Zosca'', ''Al-Zubra'' ''الزبرة'', traditional Arabic for both shoulder, and a lion's mane and ''Dhur'' ''ظهر'', the latter meaning 'back' in Arabic). ''Zosma'' means 'girdle' in

ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

, referring to the star's location in its constellation, on the hip of the

lion The lion (''Panthera leo'') is a large Felidae, cat of the genus ''Panthera'' native to Africa and India. It has a muscular, broad-chested body; short, rounded head; round ears; and a hairy tuft at the end of its tail. It is sexually dimorphi ...

. 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 catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN, which included ''Zosma'' for this star. In

Chinese Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of ...

, (), meaning '' Right Wall of Supreme Palace Enclosure'', refers to an asterism consisting of δ Leonis, β Virginis, σ Leonis, ι Leonis and θ Leonis. Consequently, the

Chinese name Chinese names or Chinese personal names are names used by individuals from Greater China and other parts of the Chinese-speaking world throughout East and Southeast Asia (ESEA). In addition, many names used in Japan, Korea and Vietnam are often a ...

for δ Leonis itself is (, en, the Fifth Star of Right Wall of Supreme Palace Enclosure), representing (), meaning ''The First Western Minister''.English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name
, Hong Kong Space Museum. Accessed on line November 23, 2010. 西上相 (Xīshǎngxiāng), spelled ''Shang Seang'' by R.H. Allen, means "the Higher Minister of State".

References

{{DEFAULTSORT:Delta Leonis A-type main-sequence stars Delta Scuti variables Ursa Major moving group Zosma Leonis, Delta Leo (constellation) Durchmusterung objects Leonis, 68 0419 054872 097603 4357