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

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

in the

zodiac The zodiac is a belt-shaped region of the sky that extends approximately 8° north and south celestial latitude of the ecliptic – the apparent path of the Sun across the celestial sphere over the course of the year. Within this zodiac ...

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 first constellati ...

of Leo. Based upon

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

measurements, it lies at a distance of about from the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

Properties

δ Leonis is a main-sequence star 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 gratin ...

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 opt ...

, 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. 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 stellar atmosphere, outer atmosphere is inflated and tenuous, making the radius large and the surface t ...

star before decaying quietly into a

remnant Remnant or remnants may refer to: Religion * Remnant (Bible), a recurring theme in the Bible * Remnant (Seventh-day Adventist belief), the remnant theme in the Seventh-day Adventist Church * ''The Remnant'' (newspaper), a traditional Catholic n ...

white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...

consisting of carbon and oxygen. 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 bu ...

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 Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

is estimated at 38.1°, which would mean the

azimuth An azimuth (; from ) is the horizontal angle from a cardinal direction, most commonly north, in a local or observer-centric spherical coordinate system. Mathematically, the relative position vector from an observer ( origin) to a point ...

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 circu ...

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 The Ursa Major Moving Group, also known as Collinder 285 and the Ursa Major association, is the closest Stellar kinematics#Moving groups, stellar moving group – a set of stars with common velocities in space and thought to have a common orig ...

, 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 alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...

. 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 classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

, 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 Sub-Saharan Africa and India. It has a muscular, broad-chested body (biology), body; a short, rounded head; round ears; and a dark, hairy tuft at the ...

. In 2016, the

International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

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, (), 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 for δ Leonis itself is (, ), 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 Ursa Major moving group Zosma Leonis, Delta Leo (constellation) Durchmusterung objects Leonis, 68 0419 054872 097603 4357