Beta Coronae Borealis
Encyclopedia
Beta Coronae Borealis (Beta CrB, β Coronae Borealis, β CrB), which has the traditional name Nusakan, is the second brightest star
in the constellation
of Corona Borealis. Although it appears to the naked eye to be a single star, it is actually a binary star
system. It is approximately 114 light-years away and has an apparent visual magnitude which varies between 3.65 and 3.72.
In Chinese
, , meaning Coiled Thong
, refers to an asterism consisting of β Coronae Borealis, π Coronae Borealis, θ Coronae Borealis, α Coronae Borealis, γ Coronae Borealis, δ Coronae Borealis, ε Coronae Borealis, ι Coronae Borealis and ρ Coronae Borealis
. Consequently, β Coronae Borealis itself is known as .
; J. B. Cannon published an orbit in 1914, finding a period of 40.9 days. Later spectroscopic investigations by F. J. Neubauer at Lick, published in 1944, found a period of 10.5 years, with no evidence for the 41-day periodicity. Antoine Labeyrie and his coworkers resolved the pair by speckle interferometry in 1973 and found that the two stars were separated by about 0.25 arcseconds; this work was published in 1974. The pair was also observed visually by Coteau in 1973. A number of orbits were subsequently published using visual and speckle-interferometric observations, both alone and in conjunction with spectroscopic data. In 1999, Söderhjelm published an orbit using speckle-interferometric data together with Hipparcos
observations.
Neubauer's 1944 work found a small variation in the radial velocity of β Coronae Borealis with a periodicity of 320 days, suggesting the presence of a third, lighter, body in the system. A 1999 study of the system by long-baseline infrared
interferometry
performed at Palomar Observatory
found no evidence for this, and showed that any tertiary companion with this period must have mass 10 Jupiter masses or below. This study also found very weak evidence for the presence of a companion with a shorter, 21-day, period, but the data was insufficient to draw a positive conclusion.
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...
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 Corona Borealis. Although it appears to the naked eye to be a single star, it is actually a binary star
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. It is approximately 114 light-years away and has an apparent visual magnitude which varies between 3.65 and 3.72.
In Chinese
Chinese language
The Chinese language is a language or language family consisting of varieties which are mutually intelligible to varying degrees. Originally the indigenous languages spoken by the Han Chinese in China, it forms one of the branches of Sino-Tibetan family of languages...
, , meaning Coiled Thong
Heavenly Market enclosure
Tian Shi Yuan, the Heavenly Market Enclosure , is one of the San Yuan or Three enclosures. Stars and constellations of this group are visible during late summer and early autumn in the Northern Hemisphere . The summer triangle lies directly to the northwest.-Asterisms:The asterisms are :...
, refers to an asterism consisting of β Coronae Borealis, π Coronae Borealis, θ Coronae Borealis, α Coronae Borealis, γ Coronae Borealis, δ Coronae Borealis, ε Coronae Borealis, ι Coronae Borealis and ρ Coronae Borealis
Rho Coronae Borealis
Rho Coronae Borealis is a Solar twin, yellow dwarf star approximately 57 light-years away in the constellation of Corona Borealis. The star is thought to be similar to the Sun with nearly the same mass, radius, and luminosity. As of 1997, an extrasolar planet has been confirmed to be orbiting the...
. Consequently, β Coronae Borealis itself is known as .
Properties
β Coronae Borealis was first announced to be a binary star in 1907, based on spectroscopic observations at Lick ObservatoryLick Observatory
The Lick Observatory is an astronomical observatory, owned and operated by the University of California. It is situated on the summit of Mount Hamilton, in the Diablo Range just east of San Jose, California, USA...
; J. B. Cannon published an orbit in 1914, finding a period of 40.9 days. Later spectroscopic investigations by F. J. Neubauer at Lick, published in 1944, found a period of 10.5 years, with no evidence for the 41-day periodicity. Antoine Labeyrie and his coworkers resolved the pair by speckle interferometry in 1973 and found that the two stars were separated by about 0.25 arcseconds; this work was published in 1974. The pair was also observed visually by Coteau in 1973. A number of orbits were subsequently published using visual and speckle-interferometric observations, both alone and in conjunction with spectroscopic data. In 1999, Söderhjelm published an orbit using speckle-interferometric data together with Hipparcos
Hipparcos
Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...
observations.
Neubauer's 1944 work found a small variation in the radial velocity of β Coronae Borealis with a periodicity of 320 days, suggesting the presence of a third, lighter, body in the system. A 1999 study of the system by long-baseline infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
interferometry
Interferometry
Interferometry refers to a family of techniques in which electromagnetic waves are superimposed in order to extract information about the waves. An instrument used to interfere waves is called an interferometer. Interferometry is an important investigative technique in the fields of astronomy,...
performed at Palomar Observatory
Palomar Observatory
Palomar Observatory is a privately owned observatory located in San Diego County, California, southeast of Pasadena's Mount Wilson Observatory, in the Palomar Mountain Range. At approximately elevation, it is owned and operated by the California Institute of Technology...
found no evidence for this, and showed that any tertiary companion with this period must have mass 10 Jupiter masses or below. This study also found very weak evidence for the presence of a companion with a shorter, 21-day, period, but the data was insufficient to draw a positive conclusion.