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Delta Indi, Latinized from δ Indi, is a binary star system in the southern constellation of Indus. It is visible to the naked eye with a combined
apparent visual 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 lig ...
of +4.40. The brighter primary, designated component A, is magnitude 4.80 while the companion, component B, is magnitude 5.96. Based upon an annual parallax shift of 14.07  mas as measured from Earth, the system is located about 188  light years from the
Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
. The binary nature of this system was discovered by South African astronomer William Stephen Finsen from 1936 onward, with his published orbital elements appearing in 1956. The pair have an
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 ...
of 12.2 years, a
semimajor axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the lo ...
of 0.176 
arc second A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The n ...
s, and an
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 ...
of around 0.03. Both components have been listed with a stellar classification of F0 IV by multiple authors, suggesting they are yellow-white hued F-type
subgiant star 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 o ...
s. However, their estimated masses don't match this classification, so Docobo and Andrade (2013) suggest the Hipparcos parallax may have been underestimated.


References

{{DEFAULTSORT:Delta Indi F-type subgiants Binary stars Indus (constellation) Indi, Delta Durchmusterung objects 208450 108431 8368