Epsilon Coronae Borealis, Latinized from ε Coronae Borealis, is a multiple star system in the

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 origins of the e ...

Corona Borealis located around 230

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s from the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

. It shines with a combined

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 4.13, meaning it is visible to the unaided eye in all night skies except those brightly lit in inner city locations. It is an orange giant around 1.7 times as massive as the Sun of spectral type K2III, which has exhausted its core fuel supply of hydrogen and swollen to 21 times the Sun's diameter and 151 times its

luminosity Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a st ...

. That is, Epsilon Coronae Borealis's diameter is about one-quarter of Mercury's orbit. Its surface temperature has been calculated to be 4365 ± 9 K, or 4406 ± 15 K. It is thought to be around 1.74 billion years old. Epsilon Coronae Borealis B is a companion star thought to be an orange dwarf of spectral types K3V to K9V that orbits at a distance of 135 astronomical units, completing one orbit every 900 years. A faint (magnitude 11.5) star, 1.5 arc minutes away, has been called Epsilon Coronae Borealis C although it is only close by line of sight and is unrelated to the system.SIMBAD
CCDM J15576+2652C -- Star in double system
(accessed 16 November 2014) The ε CrB star system's

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 temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

was observed over seven years from January 2005 to January 2012, during which time a 'wobble' with a period of around 418 days was recorded. This has been calculated to be a planet around 6.7 times 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 mass more than two and a half times that of all the other planets in the Solar System combined, but ...

orbiting at a distance of 1.3 astronomical units with an eccentricity of 0.11. Epsilon Coronae Borealis lies one degree north of (and is used as a guide for) the variable

T Coronae Borealis T Coronae Borealis (''T CrB''), is a recurring nova in the constellation Corona Borealis. It was first discovered in outburst in 1866 by John Birmingham, although it had been observed earlier as a 10th magnitude star. Description T CrB ...

References

{{DEFAULTSORT:Epsilon Coronae Borealis Corona Borealis K-type giants Coronae Borealis, Epsilon Coronae Borealis, 12 078159 143107 5947 BD+27 2558 J15573523+2652400