Tau Sagittarii Explained

Tau Sagittarii (Tau Sgr, τ Sagittarii, τ Sgr) is a star in the southern zodiac constellation of Sagittarius.

Description

With an apparent visual magnitude of +3.3, this is one of the brighter members of the constellation. The distance of this star from Earth is roughly 122abbr=offNaNabbr=off, based upon parallax measurements.

This is a spectral type K1 giant star with about . The stellar envelope is slightly cooler than the Sun with an effective temperature of 4,459 K, giving the star a light orange color. The interferometry-measured angular diameter of this star, after correcting for limb darkening, is, which, at its estimated distance, equates to a physical radius of about 16 times the radius of the Sun.

τ Sagittarii is a suspected double star although no companion has been confirmed yet. A lower metal content (Fe to H ratio is 54% lower than the sun's) and a high peculiar velocity (64 km/s, four times the local average) relative to the Sun suggest the star is a visitor from a different part of the Galaxy. ^[1]

τ  Sagittarii is a red clump giant, a star with a similar mass to the sun which has exhausted its core hydrogen, passed through the red giant branch, and started helium fusion in its core.

The Wow! signal

τ Sagittarii is the closest constellational star (a star that is part of the traditional outline of a constellation) to the origin of the 1977 Wow! signal.^[2]

Name and etymology

• The star forms part of simple asterisms:
  • γ Sgr, τ Sgr, δ Sgr, ε Sgr, ζ Sgr, λ Sgr, σ Sgr and φ Sgr — the Teapot.^[3]
  • φ Sgr, τ Sgr, ζ Sgr, χ Sgr (double) and σ Sgr — the Returning Ostriches; in Arabic Al Naʽām al Ṣādirah often transliterated as Namalsadirah (النعم السادرة).^[4]
    • Originally four stars in a numerical order: φ Sgr, τ Sgr, χ¹ Sgr and χ² Sgr^[5]
  • ν Sgr, τ Sgr, ψ Sgr, ω Sgr, 60 Sgr and ζ Sgr, Al Udḥiyy — the Ostrich's Nest.^[4]
  • In the entirely separate Chinese tradition — Chinese: 斗 (Chinese: Dǒu), meaning Dipper: τ Sgr, φ Sgr, λ Sgr, μ Sgr, σ Sgr and ζ Sgr. The star itself is Chinese: 斗宿五 (Chinese: Dǒu Xiù wǔ, English: the Dipper's fifth star).^[6]

Notes and References

1. Web site: The Teapot: A Guide to Deep Sky Objects in Sagittarius – Constellation Guide . 2023-02-09 . www.constellation-guide.com.
2. Web site: The world's biggest mysteries scientists still can't solve. 2 September 2014. 11 September 2015. 8 November 2015. https://web.archive.org/web/20151108091852/http://www.news.com.au/technology/science/the-worlds-biggest-mysteries-scientists-still-cant-solve/story-fnjwl1aw-1227045377722. dead.
3. Web site: Teapot. constellation-guide.com. 2017-05-13.
4. Book: Allen , R. H. . Richard Hinckley Allen

   . 1963 . Richard Hinckley Allen . Star Names: Their Lore and Meaning . 2012-09-04 . Reprint . Dover Publications Inc . New York . 0-486-21079-0 . 355 . registration .

5. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720005197_1972005197.pdf Jack W. Rhoads - Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology; November 15, 1971
6. AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 11 日