Upsilon Sagittarii
Encyclopedia
Upsilon Sagittarii is a spectroscopic binary star system
in the constellation
Sagittarius
. Upsilon Sagittarii is the prototypical hydrogen-deficient binary (HdB), and one of only four such systems known. The unusual spectrum
of hydrogen-deficient binaries has made stellar classification
of Upsilon Sagittarii difficult.
The primary component, Upsilon Sagittarii A, is most probably an A type
supergiant
. The radius of the primary is estimated at 60 solar radii, and its mass is estimated to be between one and thirteen solar mass
es. A is classified as an irregular variable
and experiences apparent magnitude
fluctuations between +4.51 and +4.65 with a period of approximately 20 days. Its mean apparent magnitude is +4.52.
The companion, Upsilon Sagittarii B, is more massive, but so dim at visible frequencies as to be undetectable by optical telescopes. It is probably an O or B type main sequence
dwarf, which has accreted
much of the original mass of the primary. It is estimated to have a mass of three to eleven solar mass
es.
The binary system
has an orbital period of 137.939 days and is approximately 1672 light years
from Earth
. It is predicted that Upsilon Sagittarii will end its life in a supernova
.
Star system
A star system or stellar system is a small number of stars which orbit each other, bound by gravitational attraction. A large number of stars bound by gravitation is generally called a star cluster or galaxy, although, broadly speaking, they are also star systems.-Binary star systems:A stellar...
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....
Sagittarius
Sagittarius (constellation)
Sagittarius is a constellation of the zodiac, the one containing the galactic center. Its name is Latin for the archer, and its symbol is , a stylized arrow. Sagittarius is commonly represented as a centaur drawing a bow...
. Upsilon Sagittarii is the prototypical hydrogen-deficient binary (HdB), and one of only four such systems known. The unusual spectrum
Spectrum
A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...
of hydrogen-deficient binaries has made stellar classification
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...
of Upsilon Sagittarii difficult.
The primary component, Upsilon Sagittarii A, is most probably an A 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...
supergiant
Supergiant
Supergiants are among the most massive stars. They occupy the top region of the Hertzsprung-Russell diagram. In the Yerkes spectral classification, supergiants are class Ia or Ib . They typically have bolometric absolute magnitudes between -5 and -12...
. The radius of the primary is estimated at 60 solar radii, and its mass is estimated to be between one and thirteen solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
es. A is classified as an irregular variable
Irregular variable
An irregular variable is a type of variable star in which variations in brightness show no regular periodicity. There are two main sub-types of irregular variable: eruptive and pulsating.Eruptive irregular variables are divided into three categories:...
and experiences 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...
fluctuations between +4.51 and +4.65 with a period of approximately 20 days. Its mean apparent magnitude is +4.52.
The companion, Upsilon Sagittarii B, is more massive, but so dim at visible frequencies as to be undetectable by optical telescopes. It is probably an O or B type main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
dwarf, which has accreted
Accretion (astrophysics)
In astrophysics, the term accretion is used for at least two distinct processes.The first and most common is the growth of a massive object by gravitationally attracting more matter, typically gaseous matter in an accretion disc. Accretion discs are common around smaller stars or stellar remnants...
much of the original mass of the primary. It is estimated to have a mass of three to eleven solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
es.
The binary system
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...
has an orbital period of 137.939 days and is approximately 1672 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
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
. It is predicted that Upsilon Sagittarii will end its life in a supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
.