Alpha¹ Capricorni, Latinized from α¹ Capricorni, is a distant,

binary star A binary star 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 using a telescope as separate stars, in ...

system dominated by a highly luminous star in the constellation of

Capricornus Capricornus is one of the constellations of the zodiac. Its name is Latin for "horned goat" or "goat horn" or "having horns like a goat's", and it is commonly represented in the form of a sea goat: a mythical creature that is half goat, half fi ...

, north of the

ecliptic The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic agai ...

. It has the traditional star names Prima Giedi () and Algiedi Prima (). The system is separated from the brighter Alpha² Capricorni by 0.11° of the sky, a gap resolvable with the naked eye, similar to Mizar and Alcor. Both are not to be confused with much fainter 3 Capricorni nor somewhat fainter

Nu Capricorni Nu Capricorni or ν Capricorni is a binary star system in the southern constellation of Capricornus. It is visible to the naked eye with an apparent visual magnitude of +4.76. Attributes The star system is 6.6 degrees north of the eclip ...

which are 3 to 6 times the angular distance apart than separate the two Alpha stars, respectively. The primary star is a yellow hued

supergiant Supergiants are among the most massive and most luminous stars. Supergiant stars occupy the top region of the Hertzsprung–Russell diagram with absolute visual magnitudes between about −3 and −8. The temperature range of supergiant stars s ...

star 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 G3 Ib. It has 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 li ...

of +4.3; bright enough to make it visible to the naked eye. The star is located at a distance of approximately 870 light years from the solar system based on

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 ...

measurements, but is drifting closer with a

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the rate of change of the distance or range between the two points. It is equivalent to the vector projection ...

of −25 km/s. The star is past first

dredge-up A dredge-up is any one of several stages in the evolution of some stars. By definition, during a ''dredge-up'', a convection zone extends all the way from the star's surface down to the layers of material that have undergone fusion. Consequently, ...

and has already

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 te ...

through the

Cepheid instability strip The unqualified term instability strip usually refers to a region of the Hertzsprung–Russell diagram largely occupied by several related classes of pulsating variable stars: Delta Scuti variables, SX Phoenicis variables, and rapidly oscil ...

; it may be about to do so a second time. It has 5.3 times the mass and 36 times the radius of the Sun, and is radiating around 1,047 times the Sun's luminosity from its

photosphere The photosphere is a star's outer shell from which light is radiated. The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...

at 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 5,119 K. The

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...

satellite in about the year 2000 found a previously undetected companion at an

angular separation Angular distance \theta (also known as angular separation, apparent distance, or apparent separation) is the angle between the two sightlines, or between two point objects as viewed from an observer. Angular distance appears in mathematics (in pa ...

of from the primary. This magnitude 8.60 star forms a binary pair with α¹ Capricorni. Three other faint visual companion stars lie within one arc-minute, so are unresolveable in small telescopes. The brightest of these is 10th magnitude and on this basis it has often been considered as an optical binary. Separation is increasing rapidly due to great

proper motion Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more dista ...

of the primary star.

In popular culture

The name '' Giedi Prime'' is used for a fictional planet in

Frank Herbert Franklin Patrick Herbert Jr. (October 8, 1920February 11, 1986) was an American science fiction author best known for the 1965 novel ''Dune'' and its five sequels. Though he became famous for his novels, he also wrote short stories and worked a ...

's 1965

science fiction Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imagination, imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, Paral ...

novel ''

Dune A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, fl ...

''. This Giedi Prime is a planet of the star 36 Ophiuchi B, and is the home world of the villainous

House Harkonnen Baron Vladimir Harkonnen () is a fictional character in the Dune (franchise), ''Dune'' franchise created by Frank Herbert. He is primarily featured in the 1965 novel ''Dune (novel), Dune'' and is also a prominent character in the ''Prelude to Dune ...

References

{{DEFAULTSORT:Alpha1 Capricorni G-type supergiants Double stars Capricornus (constellation) Capricorni, Alpha1 Durchmusterung objects Capricorni, 05 192876 100027 7747 Algiedi Prima

In popular culture

See also

References