Epoch J2000 Equinox J2000
|Right ascension||07h 17m 08.55678s|
|Declination||−37° 05′ 50.8962″|
|Apparent magnitude (V)||2.733|
|Spectral type||K3 Ib|
|U−B color index||+1.238|
|B−V color index||+1.608|
|Radial velocity (Rv)||+15.8 km/s|
|Proper motion (μ)||RA: −10.05 mas/yr
Dec.: +6.47 mas/yr
|Parallax (π)||4.04 ± 0.33 mas|
|Distance||810 ± 70 ly
(250 ± 20 pc)
|Absolute magnitude (MV)||4.5|
|Mass||11.7 ± 0.2 M☉|
|Age||20.0 ± 3.9 Myr|
Pi Puppis (Pi Pup, π Puppis, π Pup), also named Ahadi, is the second-brightest star in the southern constellation of Puppis. It has an apparent visual magnitude of 2.733, so it can be viewed with the naked eye at night. Parallax measurements yield an estimated distance of roughly 810 light-years (250 parsecs) from the Earth. This is a double star with a magnitude 6.86 companion at an angular separation of 0.72 arcsecond and a position angle of 148°.
The spectrum of Pi Puppis matches a stellar classification of K3 Ib. The Ib luminosity class indicates this a lower luminosity supergiant star that has consumed the hydrogen fuel at its core, evolved away from the main sequence, and expanded to about 48 times the Sun's radius. The effective temperature of the star's outer envelope is about 4,000 K, which gives it the orange hue of a K-type star. It is a semiregular variable star that varies in apparent magnitude from a high of 2.70 down to 2.85. Pi Puppis is the brightest star in the open cluster Collinder 135.
In Chinese, 弧矢 (Hú Shǐ), meaning Bow and Arrow, refers to an asterism consisting of π Puppis, δ Canis Majoris, η Canis Majoris, HD 63032, HD 65456, ο Puppis, k Puppis, ε Canis Majoris and κ Canis Majoris. Consequently, π Puppis itself is known as 弧矢九 (Hú Shǐ jiǔ, English: the Ninth Star of Bow and Arrow.)
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- 弧矢 (Hú Shǐ) is westernized into Koo She. R.H. Allen had opinion that Koo She refers to the asterism including δ Velorum and ω Velorum. AEEA opinion is, δ Velorum is member of 天社 (Tiān Shè), meaning Celestial Earth God's Temple asterism and ω Velorum is not member of any asterisms. 天社 (Tiān Shè)is westernized into Tseen She and R.H.Allen used the term Tseen She for Chinese name of η Carinae. See Richard Hinckley Allen: Star Names — Their Lore and Meaning: Argo Navis and (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 17 日.
- (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 16 日