3 Serpentis is a binary 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 ...

with an orbital period of approximately 66 years. It is dimly visible to the naked eye with an

apparent 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 ...

of 5.337. Located around distant, it is an

orange giant 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 ...

of spectral type K0III, a star that has used up its core

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

. The two components of 3 Serpentis can be resolved using

speckle interferometry Speckle imaging describes a range of high-resolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of atmospheric turbulence. They can be divided into the shift-and-add ("'' ...

and were separated by 0.23" in 2014. The orbit is highly eccentric and at

periastron An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ...

passage in 1997, the two are calculated to have been only 6 mas apart. Individual spectra for the two components of 3 Serpentis cannot be obtained and the spectral type of K0III is for the two stars combined. The primary is 2.5 magnitudes brighter than the secondary and cooler. The combined spectral type indicates that the primary is likely to have evolved away from the main sequence, but comparison of the colour and brightness of the secondary suggest it is still a main sequence star.

References

{{DEFAULTSORT:3 Serpentis Serpens Serpentis, 03 K-type giants Durchmusterung objects 5674 135482 074649 Binary stars