Theta Pyxidis

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Theta Pyxidis
Diagram showing star positions and boundaries of the Pyxis constellation and its surroundings
Cercle rouge 100%.svg

Location of θ Pyxidis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Pyxis
Right ascension 09h 21m 29.60s[1]
Declination –25° 57′ 55.5″[1]
Apparent magnitude (V) 4.72
Spectral type M0III
B−V color index 1.61
Variable type semiregular variable[2]
Radial velocity (Rv) +20.0 ± 2 km/s
Proper motion (μ) RA: –12.24 ± 0.40[1] mas/yr
Dec.: –9.29 ± 0.37[1] mas/yr
Parallax (π) 6.49 ± 0.45[1] mas
Distance 500 ± 30 ly
(150 ± 10 pc)
Radius 54[3] R
Luminosity 970[4] L
Temperature 3825[4] K
Other designations
θ Pyxidis, θ Pyx, Theta Pyx, CPD−25  4152, FK5 1243, GC 12916, HD 80874, HIP 45902, HR 3718, PPM 256035, SAO 177322.
Database references

Theta Pyxidis (Theta Pyx, θ Pyxidis, θ Pyx) is a red M-type giant in the constellation Pyxis. It is approximately 500 ± 30 light years from Earth.[1] It is of spectral type M1III and semi-regular variable with two measured periods of 13 and 98.3 days, and an average visual magnitude of 4.71,[2] It shines with a luminosity approximately 970 times that of the Sun and has a surface temperature of 3825 K.[4] It has a diameter around 54 times that of the Sun.[3]

Theta Pyxidis is moving through the Galaxy at a speed of 22.8 km/s relative to the Sun. Its projected Galactic orbit carries it between 21,200 and 24,700 light years from the center of the Galaxy. It came closest to the Sun 5.8 million years ago when it had brightened to magnitude 3.12 from a distance of 241 light years.


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752Freely accessible, doi:10.1051/0004-6361:20078357 
  2. ^ a b Tabur, V.; Bedding, T.R. (2009). "Long-term photometry and periods for 261 nearby pulsating M giants". Monthly Notices of the Royal Astronomical Society. 400 (4): 1945–61. Bibcode:2009MNRAS.400.1945T. arXiv:0908.3228Freely accessible. doi:10.1111/j.1365-2966.2009.15588.x. 
  3. ^ a b Pasinetti Fracassini, L. E.; Pastori, L.; Covino, S.; Pozzi, A. (2001). "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics". Astronomy & Astrophysics. 367: 521–24. Bibcode:2001A&A...367..521P. arXiv:astro-ph/0012289Freely accessible. doi:10.1051/0004-6361:20000451. 
  4. ^ a b c McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (2012). "Fundamental Parameters and Infrared Excesses of Hipparcos Stars". Monthly Notices of the Royal Astronomical Society. 427 (1): 343–57. Bibcode:2012MNRAS.427..343M. arXiv:1208.2037Freely accessible. doi:10.1111/j.1365-2966.2012.21873.x.