Theta Cygni (θ Cygni, θ Cyg) is a

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 ...

in the northern

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

of Cygnus. 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 4.5, so it can be seen with the naked eye in sufficiently dark skies. Based upon

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, it is at a distance of about from the

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 ...

. It is suspected of hosting an

extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first detect ...

Properties

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 the primary star matches a

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 ...

of F3 V. The

luminosity class 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 ...

'V' is associated with a category of stars called

main sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or d ...

, which, like the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

, are generating energy through the

nuclear fusion Nuclear fusion is a nuclear reaction, reaction in which two or more atomic nuclei combine to form a larger nuclei, nuclei/neutrons, neutron by-products. The difference in mass between the reactants and products is manifested as either the rele ...

of hydrogen at their cores. The outer envelope of this star is radiating 4.2 times the luminosity of the Sun 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 about 6,381 K, which gives it the yellow-white hue typical of F-type stars. Theta Cygni is larger than the

, with about 38% more mass and a 58% greater radius. The estimated age of this star is probably in the range of 0.6–1.9 billion years.

Companions

θ Cygni has several faint companions. The closest is θ Cygni B, a 13th magnitude

red dwarf A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...

around 3" distant, and believed to be in orbit around 46 AU from θ Cygni. A 12th magnitude star around an

arc minute 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 ...

distant is catalogued as component C and is believed to be an optical companion. Component D is a magnitude 12.5 star also thought to be an optical companion. GJ 765B, not to be confused with θ Cygni B, is 13th magnitude and a possible

subdwarf A subdwarf, sometimes denoted by "sd", is a star with luminosity class VI under the Yerkes spectral classification system. They are defined as stars with luminosity 1.5 to 2 magnitudes lower than that of main-sequence stars of the same ...

companion. GSC 03564-00642 is another 13th magnitude red dwarf and thought to be a common proper montion companion to θ Cygni. θ Cygni B has an apparent visual magnitude of 13.03, which is too faint to be seen without a telescope. It has a stellar classification of M3 V and an estimated mass of about 0.33 times the mass of the Sun. θ Cygni A and B are traveling together through space with a high

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 ...

of 0.261

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 per year, or 0.4° per century. It is possible that θ Cygni B is itself a close binary containing two red dwarfs, each of which would be fainter and less massive than calculated for a single star.

Possible planetary companion

Radial velocity variations of Theta Cygni have been detected by the ELODIE team while searching of extrasolar planets. Desort et al. (2009) infer these variations are not caused by a dim stellar companion roughly 80

Astronomical Units The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to . Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its mode ...

away from the star, but suggest instead the presence of a perturbing

planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...

ary object, twice as massive as

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

and orbiting around the primary star in roughly 150 days. This

has yet to be confirmed. Observations made at

Lick Observatory The Lick Observatory is an astronomical observatory owned and operated by the University of California. It is on the summit of Mount Hamilton (California), Mount Hamilton, in the Diablo Range just east of San Jose, California, United States. The ...

show evidence for radial velocity variation at this period as well as at yearly aliases, however these signals have not reached statistical significance.

References

{{Stars of Cygnus Cygnus (constellation) Cygni, Theta Cygni, 13 F-type main-sequence stars Hypothetical planetary systems 0765 096441 185395 BD+49 3062 7469 M-type main-sequence stars Kepler Input Catalog