σ Pegasi, Latinised as Sigma Pegasi, is a binary star system in the northern constellation of Pegasus. With a combined

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 5.16, it is faintly visible to the naked eye. Based upon an annual parallax shift of 36.66 mas as seen from Earth, the system is located 89 light years distant 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 ...

. It has a relatively high proper motion, advancing across the celestial sphere at the rate of 0.524 arcseconds per year. The primary, component A, is a yellow-white hued

F-type main-sequence star An F-type main-sequence star (F V) is a main-sequence, hydrogen-fusing star of spectral type F and luminosity class V. These stars have from 1.0 to 1.4 times the mass of the Sun and surface temperatures between 6,000 and 7,600 K.Tables VII ...

with a stellar classification of F6 V. However, Frasca et al. (2009) lists it as a somewhat more

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 ...

F-type

subgiant star 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 o ...

with a class of F7 IV. At the age of 2.7 billion years, it has an inactive chromosphere and is spinning with a leisurely

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 bulg ...

of 3 km/s. It has a faint, magnitude 13.23 red dwarf companion, designated component B, at an angular separation of 248

arc second A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The n ...

s. The system is most likely (96% chance) a member of the

thin disk The thin disk is a structural component of spiral and S0-type galaxies, composed of stars, gas and dust. It is the main non-centre (e.g. galactic bulge) density, of such matter. That of the Milky Way is thought to have a scale height of around ...

population of the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...

References

External links

* {{DEFAULTSORT:Sigma Pegasi F-type subgiants F-type main-sequence stars M-type main-sequence stars Binary stars Pegasus (constellation) Pegasi, Sigma Durchmusterung objects Pegasi, 49 216385 112935 8697