Gamma Delphini, which is Latinized from γ Delphini, is a wide

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 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 Delphinus. The star marks one corner of the asterism " Job's Coffin". The pair can be split with a modest amateur telescope and have been described as "one of the prettier pairs in the sky", with their contrasting colors said to be orange and lime in appearance. Together, the system is visible to the naked eye with a combined

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 3.87.

Space motion

The system is located at a distance of 115

light year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distance, astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by t ...

s from 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 ...

based on

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 ...

, but is drifting closer with a

radial velocity The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ...

of −7 km/s. It is a member of the thin disk population, and is a proposed member of the Wolf 630 moving group. This star was found to be a

double Double, The Double or Dubble may refer to: Mathematics and computing * Multiplication by 2 * Double precision, a floating-point representation of numbers that is typically 64 bits in length * A double number of the form x+yj, where j^2=+1 * A ...

by Christian Mayer and later observed by William Herschel on Sept 27th, 1779. It was later included as STF 2727 in the catalogue compiled by F. G. W. Struve and can be found under this name in the Washington Double Star Catalog. At the time, the components had 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 along 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 ...

(PA) of 280°. As of 2019, they are separated by with a PA of 265°. The fainter component, designated γ¹ Delphini, is of

apparent magnitude Apparent magnitude () is a measure of the Irradiance, 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 (astronomy), ...

5.03. Its companion is a magnitude 4.360 star designated γ² Delphini. A fit of

orbital elements Orbital elements are the parameters required to uniquely identify a specific orbit. In celestial mechanics these elements are considered in two-body systems using a Kepler orbit. There are many different ways to mathematically describe the same o ...

to the available positional data provides a period of 3,249 years with a high

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 ...

(ovalness) of 0.88. Their physical separation ranges from roughly 40 out to .

Physical properties

The

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 γ¹ Delphini is F7V, which matches an

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 ...

with a yellow-white hue. It is about 1.8 billion years old and is spinning with a

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 bu ...

of 7.8 km/s. The star has 1.6 times the mass and 2.6 times the radius of the Sun. It is radiating 10 times the Sun's luminosity from its

photosphere The photosphere is a star's outer shell from which light is radiated. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately , or equivalently, a depth from which 50% of light will esc ...

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 6,295 K. The brighter component, γ² Delphini, has an orange hue with a class of K1IV. Being the more massive star of the pair, it is the more

evolved Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...

star and is currently on the

subgiant branch 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 of ...

. It has double the mass of the Sun but has expanded to over eight times the Sun's radius. The star is radiating 33 times the luminosity of the Sun at 4,798 K. It is spinning with a

of 3.6 km/s. The star displays a radial acceleration with a periodicity of 1.44 years, which may be the effect of an orbiting companion. The system is a source of X-ray emission with high probability.

Search for planets

In 1999, the presence of a planetary companion was inferred around Gamma² Delphini as one possible explanation for the radial velocity variations. Such a planet would have a minimum mass of 0.7

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 ...

masses, orbital period of 1.44 years and separation of nearly 1.5

astronomical unit 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 m ...

s (almost the orbital separation of

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

from the

). The planetary candidate has not been confirmed. McDonald Observatory researches have set mass limits for potential planetary companions in orbit around the star Gamma² Delphini.

References

External links

* {{DEFAULTSORT:Gamma Delphini F-type main-sequence stars K-type subgiants Hypothetical planetary systems Binary stars Delphinus Delphini, Gamma BD+15 4255 Delphini, 12 197963 4 102531/2 7947/8