Eta Serpentis, Latinized from η Serpentis, 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

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 ...

Serpens Serpens () is a constellation in the northern celestial hemisphere. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it remains one of the 88 modern constellations designated by the International Astronomical Union. It ...

. In particular, it lies in Serpens Cauda, the snake's tail. The star has an

apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction of the object's light ca ...

of 3.260, making it visible to the naked eye.

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 give a distance estimate of from the Earth. This star is larger than 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 ...

, with 1.6 times the mass and almost six times the radius. The

spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...

matches 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 K0 III-IV, with the

luminosity class 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 III-IV corresponding to an

evolved Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...

star that lies between the

subgiant A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution ...

and

giant In folklore, giants (from Ancient Greek: ''wiktionary:gigas, gigas'', cognate wiktionary:giga-, giga-) are beings of humanoid appearance, but are at times prodigious in size and strength or bear an otherwise notable appearance. The word ''gia ...

stages. The expanded outer envelope star is radiating about 18 times the

luminosity of the Sun The solar luminosity () is a unit of radiant flux ( power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun. One nominal s ...

at 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 . At this temperature, it has an orange hue typical of a

K-type star In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

. Eta Serpentis displays

solar-like oscillations Solar-like oscillations are oscillations in 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 ot ...

with a period of 0.09 of a day. Eta Serpentis was previously classified as a

carbon star A carbon star (C-type star) is typically an asymptotic giant branch star, a luminous red giant, whose Stellar atmosphere, atmosphere contains more carbon than oxygen. The two elements combine in the upper layers of the star, forming carbon monox ...

, which would have made it the brightest carbon star in the sky, although this classification was since found to be erroneous. Eta Serpentis is currently 1.6 light-years away from

Gliese 710 Gliese 710, or HIP 89825, is an orange star in the constellation Serpens Cauda. It is projected to pass near the Sun in about 1.29 million years at a predicted minimum distance of 0.051 parsecs— (about 1.6 trillion km)—about 1/25th o ...

Name

Chinese astronomy Astronomy in China has a long history stretching from the Shang dynasty, being refined over a period of more than 3,000 years. The Ancient China, ancient Chinese people have identified stars from 1300 BCE, as Chinese star names later categori ...

, the star is known as (), meaning 'Left Wall of

Heavenly Market Enclosure The Heavenly Market Enclosure (天市垣, ''Tian Shi Yuan''), is one of the ''San Yuan'' or Three enclosures. Stars and constellations of this group are visible during late summer and early autumn in the Northern Hemisphere (late winter and early ...

'; the name refers to an asterism that represents eleven old states in China. The leftmost borderline of the enclosure consists of η Serpentis,

δ Herculis Delta Herculis (δ Herculis, abbreviated Delta Her, δ Her) is a multiple star system in the constellation of Hercules. Its light produces to us apparent magnitude 3.12, as such the third-brightest star in the large, fairly dim constella ...

λ Herculis Lambda Herculis (λ Herculis. abbreviated Lambda Her, λ Her), formally named Maasym , is a star in the constellation of Hercules. From parallax measurements taken during the Gaia mission, it is approximately 393 light-years from the Sun. ...

, μ Herculis, o Herculis,

112 Herculis 112 Herculis is a binary star system in the northern constellation of Hercules. It is dimly visible to the naked eye with a combined apparent visual magnitude of 5.43. The secondary component is about two magnitudes fainter than the prim ...

η Ophiuchi Eta Ophiuchi (η Ophiuchi, abbreviated Eta Oph, η Oph) is a binary star in the constellation of Ophiuchus. With a combined apparent magnitude of +2.43, it is the second-brightest of the constellation and one of the brightest stars in th ...

ζ Aquilae Zeta Aquilae is a binary star system in the equatorial constellation of Aquila (constellation), Aquila. Its name is a Bayer designation that is Romanization of Greek, Latinized from ζ Aquilae, and abbreviated Zeta Aql or ζ Aql. This sys ...

, θ¹ Serpentis, ν Ophiuchi and ξ Serpentis. Consequently, the

Chinese name Chinese may refer to: * Something related to China * Chinese people, people identified with China, through nationality, citizenship, and/or ethnicity **Han Chinese, East Asian ethnic group native to China. **'' Zhonghua minzu'', the supra-ethni ...

for η Serpentis itself is (, ''the Eighth Star of Left Wall of Heavenly Market Enclosure'', representing the region of Donghai (東海, lit. meaning 'eastern sea'),English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name
, Hong Kong Space Museum. Accessed on line November 23, 2010.

References

{{Stars of Serpens K-type giants Serpens Serpentis, Eta Durchmusterung objects Serpentis, 58 168723 089962 6869