Astronomy:PZ Telescopii

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Short description: Star in the constellation Telescopium
PZ Telescopii
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An image taken by the Gemini South telescope showing PZ Tel A and its brown dwarf companion PZ Tel B. Image analysis techniques were used to remove the vast majority of light from PZ Tel A.[1]
Observation data
Equinox J2000.0]] (ICRS)
Constellation Telescopium
Right ascension  18h 53m 05.87351s[2]
Declination −50° 10′ 49.8974″[2]
Apparent magnitude (V) 8.33 - 8.63[3]
Characteristics
Evolutionary stage Pre-main-sequence star[4]
Spectral type G9 IV[5] + M7±1[6]
B−V color index +0.784±0.021[7]
Variable type BY Dra[3]
Astrometry
Radial velocity (Rv)−0.01+0.12
−0.02[8] km/s
Proper motion (μ) RA: +16.272(18)[2] mas/yr
Dec.: −85.519(17)[2] mas/yr
Parallax (π)21.1621 ± 0.0223[2] mas
Distance154.1 ± 0.2 ly
(47.25 ± 0.05 pc)
Absolute magnitude (MV)4.88[7]
Orbit[8]
Period (P)140+42
−24 yr
Semi-major axis (a)28.3+4.6
−2.6 astronomical unit|AU
Eccentricity (e)0.576+0.052
−0.054
Inclination (i)91.63+0.21
−0.20°
Longitude of the node (Ω)58.91+0.12
−0.13 or 238.78+0.12
−0.13°
Periastron epoch (T)1997.2+4.7
−1.8[9]
Argument of periastron (ω)
(secondary)		38+14
−10 or 234+13
−11°
Details
Mass1.142+0.086
−0.081[8] M☉
Radius1.23±0.04[10] R☉
Luminosity0.993+0.004
−0.005[11] L☉
Surface gravity (log g)4.41±0.10[10] cgs
Temperature5,338±200[10] K
Metallicity [Fe/H]+0.05±0.20[10] dex
Rotation0.943±0.002[6] days
Rotational velocity (v sin i)69.0±0.1[5] km/s
Age24±3[10] Myr
B
Mass24.0+9.5
−7.3[8] MJup
Radius2.42+0.38
−0.34[4] RJup
Surface gravity (log g)< 4.5[6] cgs
Temperature2,700±100[10] K
Other designations
PZ Tel, CD−50°12190, HD 174429, HIP 92680, SAO 245781, PPM 347231, WDS J18531-5011AB[12]
Database references
SIMBADdata

PZ Telescopii, also known as HD 174429 or simply PZ Tel, is a young star in the constellation Telescopium. Based on parallax measurements, it is located at a distance of 154 light-years from the Sun. It is too faint to be visible to the naked eye, yet it is one of the closest and hence brightest pre-main-sequence stars to Earth.[10]

In 1980, Denis Walter Coates et al. announced that the star, then known as HD 174429, is a variable star.[13] It was given its variable star designation, PZ Telescopii, in 1981.[14] It is classified as a BY Draconis variable that ranges in apparent visual magnitude from 8.33 down to 8.63 over a period of 22.581 hours (0.94088 days).[3]

PZ Telescopii has an effective surface temperature of around 5,338 K (the Sun has an approximate surface temperature of 5,778 K), a mass around 1.13 times, and diameter 1.23 times that of the Sun.[10] The star has a high rate of spin, showing a projected rotational velocity of 69 km/s[5] and a rotation period of 22.6 h.[6] It is radiating about the same luminosity as the Sun. PZ Telescopii was originally considered to be a member of the Beta Pictoris moving group; however in a 2012 paper, James Jenkins of Universidad de Chile and colleagues used three methods to calculate its age and came up with a figure of around 24 million years—significantly older than the 12 million years of the association.[10]

This star has an orbiting debris disk calculated to span from a radius of 35 to 165 astronomical units (AU), as well as a substellar companion with about 28 or 36 times the mass of Jupiter orbiting at a distance of about 16 AU, discovered in 2009 independently by two teams.[15][16] The companion, currently known as PZ Tel B, is thought to be a brown dwarf; however it is possible (though very unlikely) that it is an extremely large Jupiter-like planet,[4] in which case it would be PZ Tel b, and the first such planet to be directly imaged.[10] Preliminary orbital elements from 2016 give a best fit orbital period of 622.2 years with an eccentricity of 0.755.[6]

The mass and orbit of this companion were updated in 2023 based on Hipparcos and Gaia astrometry, finding a somewhat lower mass, and an edge-on orbit that is eccentric but less so than previous results.[9] It is now included in the NASA Exoplanet Archive since its nominal mass of 27 |♃|J}}}}}} is below their upper limit of 30 MJ, although the margin of error is large enough that it is still possible that the mass exceeds 30 MJ.[17][18] Updated values were provided in 2026, providing tighter constraints in the mass and orbit of PZ Telescopii b.[8]

Visual band light curves for PZ Telescopii, adapted from Innis et al. (1990)[19]

References

  1. ↑ "An unusual Brown Dwarf" (Press release). NOIRLab. 2010-09-30. Retrieved 2025-06-13.
  2. ↑ 2.0 2.1 2.2 2.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 Samus, N. N. et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1 61 (1): 80–88. doi:10.1134/S1063772917010085. Bibcode: 2017ARep...61...80S. 
  4. ↑ 4.0 4.1 4.2 Schmidt, T. O. B.; Mugrauer, M.; Neuhäuser, R.; Vogt, N.; Witte, S.; Hauschildt, P. H.; Helling, Ch.; Seifahrt, A. (June 2014). "First spectroscopic observations of the substellar companion of the young debris disk star PZ Telescopii". Astronomy & Astrophysics 566: A85. doi:10.1051/0004-6361/201321625. ISSN 0004-6361. Bibcode: 2014A&A...566A..85S. http://www.aanda.org/10.1051/0004-6361/201321625. 
  5. ↑ 5.0 5.1 5.2 Torres, C. A. O.; Quast, G. R.; Silva, L. da; Reza, R. de la; Melo, C. H. F.; Sterzik, M. (December 1, 2006). "Search for associations containing young stars (SACY) - I. Sample and searching method" (in en). Astronomy & Astrophysics 460 (3): 695–708. doi:10.1051/0004-6361:20065602. ISSN 0004-6361. Bibcode: 2006A&A...460..695T. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 Maire, A. -L. et al. (March 2016). "First light of the VLT planet finder SPHERE. II. The physical properties and the architecture of the young systems PZ Telescopii and HD 1160 revisited". Astronomy & Astrophysics 587: 24. doi:10.1051/0004-6361/201526594. A56. Bibcode: 2016A&A...587A..56M. 
  7. ↑ 7.0 7.1 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A. 
  8. ↑ 8.0 8.1 8.2 8.3 8.4 Bernardi, Andrea; Zurlo, Alice; Lazzoni, Cecilia; Desidera, Silvano; Mesa, Dino; Pérez, Sebastian; Nogueira, Pedro Henrique; Barbato, Domenico; Dasgupta, Anuroop (2026-07-15). "SaNDi-SHoP: Searching for Satellites'N'Disks with a Star-Hopping Program II. Spectrophotometric analysis and orbital monitoring of directly imaged companions". arXiv:2607.13545 [astro-ph.EP].
  9. ↑ 9.0 9.1 Franson, Kyle; Bowler, Brendan P. (June 2023). "Dynamical Mass of the Young Brown Dwarf Companion PZ Tel B". The Astronomical Journal 165 (6): 246. doi:10.3847/1538-3881/acca18. Bibcode: 2023AJ....165..246F. 
  10. ↑ 10.00 10.01 10.02 10.03 10.04 10.05 10.06 10.07 10.08 10.09 Jenkins, J. S.; Pavlenko, Y. V.; Ivanyuk, O.; Gallardo, J. et al. (2012). "Benchmark Cool Companions: Ages and Abundances for the PZ Telescopii System". Monthly Notices of the Royal Astronomical Society 420 (4): 3587–98. doi:10.1111/j.1365-2966.2011.20280.x. Bibcode: 2012MNRAS.420.3587J. 
  11. ↑ Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  12. ↑ "V* PZ Tel". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=V%2A+PZ+Tel. 
  13. ↑ Coates, D. W.; Halprin, L.; Sartori, P.; Thompson, K. (September 1980). "Optical Variability of the RS CVn Candidate HD 174429". Information Bulletin on Variable Stars 1849: 1–2. Bibcode: 1980IBVS.1849....1C. https://ibvs.konkoly.hu/pub/ibvs/1801/1849.pdf. Retrieved 30 August 2025. 
  14. ↑ Kholopov, P. N.; Samus, N. N.; Kukarkina, N. P.; Medvedeva, G. I.; Perova, N. B. (November 1981). "66th Name-List of Variable Stars". Information Bulletin on Variable Stars 2042: 1–7. Bibcode: 1981IBVS.2042....1K. https://ibvs.konkoly.hu/pub/ibvs/2001/2042.pdf. Retrieved 30 August 2025. 
  15. ↑ Biller, Beth A. et al. (September 2010). "The Gemini NICI Planet-finding Campaign: Discovery of a Close Substellar Companion to the Young Debris Disk Star PZ Tel". The Astrophysical Journal Letters 720 (1): L82–L87. doi:10.1088/2041-8205/720/1/L82. Bibcode: 2010ApJ...720L..82B. 
  16. ↑ Mugrauer, M.; Vogt, N.; Neuhäuser, R.; Schmidt, T. O. B. (November 2010). "Direct detection of a substellar companion to the young nearby star PZ Telescopii". Astronomy & Astrophysics 523: L1. doi:10.1051/0004-6361/201015523. ISSN 0004-6361. Bibcode: 2010A&A...523L...1M. http://www.aanda.org/10.1051/0004-6361/201015523. 
  17. ↑ "PZ Tel". NASA Exoplanet Archive. https://exoplanetarchive.ipac.caltech.edu/overview/PZ%20Tel. 
  18. ↑ "Exoplanet Criteria for Inclusion in the Archive". NASA Exoplanet Archive. https://exoplanetarchive.ipac.caltech.edu/docs/exoplanet_criteria.html. 
  19. ↑ Innis, J. L.; Coates, D. W.; Thompson, K.; Lloyd Evans, T. (January 1990). "Observations of active-chromosphere stars III - photometry of PZ Tel 1979-1985". Monthly Notices of the Royal Astronomical Society 242 (3): 306–310. doi:10.1093/mnras/242.3.306. Bibcode: 1990MNRAS.242..306I. 



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