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J20000
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Sagittarius
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19<sup>h</sup> 21<sup>m</sup> 436<sup>s</sup>
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-15° 57' 18"
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B2Vpe+A2IaShell
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+452
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1673 ± 618
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513 ± 189
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(υ Sgr / υ 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, , is most likely 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, , is more massive, but so dim at
Visible Frequencies as to be undetectable by optical telescopes. It is likely 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 1440
Light Years from
Earth . It is predicted that Upsilon Sagittarii will end its life in a
Supernova .
Dudley, R. E., Jeffery, C. S., 1990. ''Mon. Not. R. astr. Soc.'' , 400
