Gamma Delphini
Encyclopedia
Gamma Delphini (γ Del, γ Delphini) is a binary star
system approximately 101 light-year
s away in the constellation
of Delphinus
. The star marks one corner of the asterism
"Job's Coffin". It is one of the best known double stars in the sky, with the primary star being a yellow-white dwarf
star
, while the secondary star is an orange subgiant star.
star
of spectral type "F7V" and an apparent magnitude
of 5.14. The star is thought to have about 7 times more luminosity
than the Sun
. The secondary star (Gamma2 Delphini) is an orange subgiant star of spectral type "K1IV" and an apparent magnitude of 4.27. This star is thought to have about 20.6 times more luminosity than the Sun. Nevertheless the cooler component (Gamma2) is more massive than Gamma1 and according to the hierarchy of masses and brightness, Gamma2 should be the primary star of the system.
. Such a planet would yield a minimum mass of 0.7 Jupiter
masses, orbital period of 1.44 years and separation of nearly 1.5 astronomical unit
s (almost the orbital separation of Mars
from the Sun
).
So far 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.
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
system approximately 101 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s away in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Delphinus
Delphinus
Delphinus is a constellation in the northern sky, close to the celestial equator. Its name is Latin for dolphin. Delphinus was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains among the 88 modern constellations recognized by the International Astronomical...
. The star marks one corner of the asterism
Asterism (astronomy)
In astronomy, an asterism is a pattern of stars recognized on Earth's night sky. It may form part of an official constellation, or be composed of stars from more than one. Like constellations, asterisms are in most cases composed of stars which, while they are visible in the same general direction,...
"Job's Coffin". It is one of the best known double stars in the sky, with the primary star being a yellow-white dwarf
Yellow-white dwarf
An F-type main-sequence star 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 VII and VIII. This temperature range gives the F-type stars a...
star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
, while the secondary star is an orange subgiant star.
Stellar components
The primary star (catalogued as Gamma1 Delphini) is a yellow-white dwarfYellow-white dwarf
An F-type main-sequence star 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 VII and VIII. This temperature range gives the F-type stars a...
star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
of spectral type "F7V" and an apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of 5.14. The star is thought to have about 7 times more luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
than the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
. The secondary star (Gamma2 Delphini) is an orange subgiant star of spectral type "K1IV" and an apparent magnitude of 4.27. This star is thought to have about 20.6 times more luminosity than the Sun. Nevertheless the cooler component (Gamma2) is more massive than Gamma1 and according to the hierarchy of masses and brightness, Gamma2 should be the primary star of the system.
A planetary system?
Back in 1999 the presence of a planetary companion was inferred around Gamma2 Delphini, an evolved orange subgiant starSubgiant star
A subgiant star is a star that is slightly brighter than a normal main-sequence star of the same spectral class, but not as bright as true giant stars...
. Such a planet would yield a minimum mass of 0.7 Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
masses, orbital period of 1.44 years and separation of nearly 1.5 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s (almost the orbital separation of Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
from the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
).
So far 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.