Sigma Puppis, Latinized from σ Puppis, is a

binary star A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...

system in the southern constellation

Puppis Puppis ("poop deck, stern") is a constellation in the southern sky. It was originally part of the Former constellations, traditional constellation of Argo Navis (the ship of Jason and the Argonauts), which was divided into three parts, the other ...

. It 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 3.25, which is bright enough to be visible to the naked eye at night from the Southern Hemisphere. Through a telescope, it appears as a bright, orange-hued

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 ...

with a nearby white companion.

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 indicate this star is located at a distance of about from

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

This is a

spectroscopic binary A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...

system, consisting of an

orbit In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...

ing pair of stars that have not been individually resolved with a telescope. Their

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

is 257.8 days and the

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

is 0.17. The pair form an eclipsing binary of the Beta Lyrae type and a period of 130.5 days, or one half of their orbital period. The eclipse of the primary component causes a decline of 0.04 of a magnitude, while the secondary eclipse reduces the magnitude by 0.03. The combined

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 ...

is K5 III, which matches 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 ...

of a

giant star A giant star has a substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature. They lie above the main sequence (luminosity class V in the Yerkes spectral classification) on the Hertzsp ...

. The primary is 44 times larger than the Sun and 340 times more luminous. Its surface has 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 , giving it the orange hue 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 ...

. It shows the behavior of a

slow irregular variable A slow irregular variable (ascribed the GCVS types L, LB and LC) is a variable star that exhibit no or very poorly defined periodicity in their slowly changing light emissions. These stars have often been little-studied, and once more is learnt a ...

. In addition to its binary components, Sigma Puppis has a more distant companion that has a matching

proper motion Proper motion is the astrometric measure of changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...

, suggesting that it may be gravitationally bound to the binary. This magnitude 8.5 star is at an

angular separation Angular distance or angular separation is the measure of the angle between the orientation of two straight lines, rays, or vectors in three-dimensional space, or the central angle subtended by the radii through two points on a sphere. When t ...

of 22.4

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

s with a

position angle In astronomy, position angle (usually abbreviated PA) is the convention for measuring angles on the sky. The International Astronomical Union defines it as the angle measured relative to the Celestial pole, north celestial pole (NCP), turning pos ...

of 74° from Sigma Puppis, which is equivalent to a

projected separation This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outs ...

of . In 1970, American astronomer Olin J. Eggen suggested that Sigma Puppis belonged to a

moving group In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space. Stellar kinematics encompasses the measurement of stellar velocities in the Milky Way and its satellites as well as ...

of stars that share a similar motion through space, and thereby a common origin. It served as the

eponym An eponym is a noun after which or for which someone or something is, or is believed to be, named. Adjectives derived from the word ''eponym'' include ''eponymous'' and ''eponymic''. Eponyms are commonly used for time periods, places, innovati ...

for this, the σ Puppis group. The existence of this group was later brought into question. The

SIMBAD SIMBAD (the Set of Identifications, Measurements and Bibliography for Astronomical Data) is an astronomy, astronomical database of objects beyond the Solar System. It is maintained by the Centre de données astronomiques de Strasbourg (CDS), Fr ...

database lists the name "Hadir" for this star, of unclear origin.

References

{{DEFAULTSORT:Sigma Puppis K-type giants Beta Lyrae variables Slow irregular variables Spectroscopic binaries Puppis Puppis, Sigma CD-43 03260 059717 036377 2878