Sigma Arae (σ Ara, σ Arae) is the

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. T ...

for a

star A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make ...

in the southern constellation of

Ara ARA may refer to: Media and the arts * American-Romanian Academy of Arts and Sciences * '' Artistička Radna Akcija'', compilation album released in former Yugoslavia * Associate of the Royal Academy, denoting membership in the British Royal Acad ...

. It is visible to the naked eye with 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 +4.575. The distance to this star, based upon an annual

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

shift of 8.62 mas, is around . This is an

A-type main sequence star An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 ...

with a

stellar classification 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 t ...

of A0 V. Unusually for an

A-type star An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 ...

, X-ray emissions with a luminosity of have been detected from Sigma Arae. Normally this is explained by the presence of a lower mass orbiting companion star. However, such a scenario does not appear to hold true for this star. Instead, the signature of a surface

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and t ...

has been detected with a strength of roughly , indicating the source of the X-rays may be surface magnetic activity.

References

External links

Simbad

Image Sigma Arae
{{DEFAULTSORT:Sigma Arae 159217 Arae, Sigma Ara (constellation) A-type main-sequence stars 086092 6537 Durchmusterung objects