Eta Serpentis, Latinized from η Serpentis, is a star in the constellation

Serpens Serpens ( grc, , , the Serpent) 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 ...

. 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 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 3.260, making it visible to the naked eye. Parallax measurements give a distance estimate of from the Earth. This star is larger than 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 ...

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

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 ...

matches a stellar classification of K0 III-IV, with the

luminosity class 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 ...

of III-IV corresponding to an

evolved Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

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: ''gigas'', cognate giga-) are beings of human-like appearance, but are at times prodigious in size and strength or bear an otherwise notable appearance. The word ''giant'' is first attested in 1297 fr ...

stages. The expanded outer envelope star is radiating about 19 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 ...

at an effective 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 stars that are excited in the same way as those in the Sun, namely by turbulent convection in its outer layers. Stars that show solar-like oscillations are called solar-like oscillators. The oscillations a ...

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

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 Chinese people have identified stars from 1300 BCE, as Chinese star names later categorized in the twe ...

, 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, λ Herculis, μ Herculis, o Herculis, 112 Herculis, η Ophiuchi, ζ Aquilae, θ¹ Serpentis, ν Ophiuchi and ξ Serpentis. 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 ofte ...

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 (constellation) Serpentis, Eta Durchmusterung objects Serpentis, 58 168723 089962 6869