Beta Boötis
Encyclopedia
Beta Boötis is a variable star
in the constellation
Boötes
. It is a yellow G-type
giant
with an apparent magnitude
of +3.49. The traditional name Nakkar or Nekkar is based upon the Arabic
name for the constellation. This is a mis-transliteration of the Arabic
بقّار baqqār "cattle driver", the Arabic letters b and n differing only in the placement of the dot. In the modern constellation, it marks the head of Boötis the herdsman. This star is approximately 225 light years
from Earth.
This star has more than three times the mass of the Sun
and greater than 21 times the Sun's radius. The estimated age is , which is oddly younger than the expected age of a post-main sequence, giant star of this mass. The reason for this discrepancy is unexplained. It has an estimated rotation period of about 200 days and is inclined to the line of sight from the Earth. In 1993, the ROSAT
satellite was used to observe an X-ray flare on Beta Boötis, which released an estimated . This was the first such observation for a low-activity star of this type. The flare may be explained by an as yet unobserved M-type dwarf
companion star.
Variable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching 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....
Boötes
Boötes
Boötes is a constellation in the northern sky, located between 0° and +60° declination, and 13 and 16 hours of right ascension on the celestial sphere. The name comes from the Greek Βοώτης, Boōtēs, meaning herdsman or plowman...
. It is a yellow G-type
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...
giant
Giant star
A giant star is a star with substantially larger radius and luminosity than a main sequence star of the same surface temperature. Typically, giant stars have radii between 10 and 100 solar radii and luminosities between 10 and 1,000 times that of the Sun. Stars still more luminous than giants are...
with 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 +3.49. The traditional name Nakkar or Nekkar is based upon the Arabic
Arabic language
Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...
name for the constellation. This is a mis-transliteration of the Arabic
Arabic language
Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...
بقّار baqqār "cattle driver", the Arabic letters b and n differing only in the placement of the dot. In the modern constellation, it marks the head of Boötis the herdsman. This star is approximately 225 light years
Light Years
Light Years is the seventh studio album by Australian recording artist Kylie Minogue. It was released on 25 September 2000 by Parlophone and Mushroom Records. The album's style was indicative of her return to "mainstream pop dance tunes"....
from Earth.
This star has more than three times the mass of the Sun
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
and greater than 21 times the Sun's radius. The estimated age is , which is oddly younger than the expected age of a post-main sequence, giant star of this mass. The reason for this discrepancy is unexplained. It has an estimated rotation period of about 200 days and is inclined to the line of sight from the Earth. In 1993, the ROSAT
ROSAT
ROSAT was a German Aerospace Center-led satellite X-ray telescope, with instruments built by Germany, the UK and the US...
satellite was used to observe an X-ray flare on Beta Boötis, which released an estimated . This was the first such observation for a low-activity star of this type. The flare may be explained by an as yet unobserved M-type dwarf
Red dwarf
According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type....
companion star.