Psi1 Draconis

From the Science Archives, the open-project database of science information
Jump to navigation Jump to search

ψ¹ Draconis
Psi1 Draconis.jpg
ψ¹ Draconis in optical light
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
ψ¹ Dra A
Right ascension 17h 41m 56.35536s[1]
Declination +72° 08′ 55.8481″[1]
Apparent magnitude (V) 4.58[2]
ψ¹ Dra B
Right ascension 17h 41m 58.10460s[1]
Declination +72° 09′ 24.8581″[1]
Apparent magnitude (V) 5.82[3]
ψ¹ Dra A
Spectral type F5IV-V[4]
U−B color index +0.01[2]
B−V color index +0.43[2]
ψ¹ Dra B
Spectral type F8V[5]
U−B color index +0.04[2]
B−V color index +0.525[2]
ψ¹ Dra A
Radial velocity (Rv)-13.30 ± 0.2[6] km/s
Proper motion (μ) RA: 25.32[1] mas/yr
Dec.: -268.47[1] mas/yr
Parallax (π)43.79 ± 0.45[1] mas
Distance74.5 ± 0.8 ly
(22.8 ± 0.2 pc)
ψ¹ Dra B
Radial velocity (Rv)-11.20 ± 0.3[6] km/s
Proper motion (μ) RA: 34.89[1] mas/yr
Dec.: -275.94[1] mas/yr
Parallax (π)43.36 ± 0.51[1] mas
Distance75.2 ± 0.9 ly
(23.1 ± 0.3 pc)
Primaryψ¹ Dra Aa
Companionψ¹ Dra Ab
Period (P)6774+271
Semi-major axis (a)9.1+0.4
Eccentricity (e)0.679+0.006
Inclination (i)31 ± 1°
Periastron epoch (T)2450388+169
Argument of periastron (ω)
32.6 ± 0.7°
Semi-amplitude (K1)
Semi-amplitude (K2)
11.1 ± 0.2 km/s
ψ¹ Dra A
/ 0.70 ± 0.07[7] M
Radius1.2—1.3[8] R
Diameter1.2—1.3[8] D
Surface gravity (log g)3.90 ± 0.11[9] cgs
Temperature6544 ± 42 / 4400 ± 300[7] K
Metallicity [Fe/H]−0.10 ± 0.05[9] dex
ψ¹ Dra B
Mass1.19 ± 0.07[9] M
Radius1.5[8] R
Surface gravity (log g)4.20 ± 0.12[9] cgs
Temperature6212 ± 75[9] K
Age3.3 ± 1.0[9] years
Other designations
31 Dra, ADS 10759 AB, Gliese 694.1
ψ¹ Dra A: BD+72° 804, HD 162003, HIP 86614, HR 6636, SAO 8890[4]
ψ¹ Dra B: BD+72° 805, HD 162004, HIP 86620, HR 6637, SAO 8891[5]
Database references
ψ¹ Dra A
ψ¹ Dra B

Psi¹ Draconis (ψ¹ Draconis, abbreviated Psi¹ Dra, ψ¹ Dra), also designated 31 Draconis, is a triple star system in the northern constellation of Draco. The system is fairly close, and is located about 75 light-years (23 parsecs) from the Sun, based on its parallax.[1]

Psi¹ Draconis was considered a binary star consisting of a F-type subgiant and a F-type main-sequence star, designated Psi¹ Draconis A (also named Dziban[10]) and Psi¹ Draconis B, respectively. In 2015, Psi¹ Draconis A was itself found to be a double-lined spectroscopic binary, making the system a triple. The companion to Psi¹ Draconis A was designated Psi¹ Draconis C by its discoverers.[7]

Also in 2015, Psi¹ Draconis B was discovered to be orbited by an exoplanet, designated Psi¹ Draconis Bb.[9]


ψ¹ Draconis (Latinised to Psi¹ Draconis) is the system's Bayer designation and 31 Draconis its Flamsteed designation. The designation of the components – ψ¹ Draconis A and B – derives from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[11]

Psi¹ Draconis bore the traditional name of Dziban or Dsiban, derived from the Arabic Adh-Dhi'ban, meaning "The two wolves" or "The two jackals".[12] In 2016, the IAU organized a Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[14] It approved the name Dziban for the component Psi¹ Draconis A on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[10]

In Chinese astronomy, Psi¹ Draconis is called 女史, Pinyin: Nǚshǐ, meaning Female Protocol, because this star is marking itself and stands alone in the asterism Female Protocol in the Purple Forbidden enclosure (see Chinese constellation).[15] 女史 (Nǚshǐ) has been Latinised into Niu She by R.H. Allen, meaning "the Palace Governess", or "a Literary Woman".[12]


ψ¹ Draconis AC and ψ¹ Draconis B are separated by about 31 arcseconds. Only a very small fraction of the orbit has been observed: an orbit of with a period 10,000 years has been calculated,[16] but it is extremely preliminary and likely to be in high error.

ψ¹ Draconis A and C have varying radial velocities in respect to Earth, indicating that there must be orbital motion. The orbital period is estimated to be around 20 years, and the eccentricity must be fairly high, around 0.679.[7]


Psi¹ Draconis Bb is a Jupiter-like exoplanet orbiting Psi¹ Draconis B, the secondary star. The planet was discovered when periodic Doppler shifts in the star's spectrum revealed the presence of a planet, similar to the spectroscopic binary nature of Psi¹ Draconis AC. Its minimum mass is 1.53 MJ, and it orbits its host star every 8.5 years taking a relatively eccentric orbit.[9]

The ψ¹ Draconis B planetary system[9]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b ≥1.53 ± 0.10 MJ 4.43 ± 0.04 3117 ± 42s 0.40 ± 0.05


  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. arXiv:0708.1752. Bibcode 2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. 2.0 2.1 2.2 2.3 2.4 Johnson, H. L. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory 4: 99. Bibcode 1966CoLPL...4...99J.
  3. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV data. Bibcode 1986EgUBV........0M.
  4. 4.0 4.1 Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  5. 5.0 5.1 Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  6. 6.0 6.1 Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters 32 (11): 759–771. arXiv:1606.08053. Bibcode 2006AstL...32..759G. doi:10.1134/S1063773706110065.
  7. 7.0 7.1 7.2 7.3 7.4 Gullikson, Kevin; Endl, Michael; Cochran, William D.; MacQueen, Phillip J. (2015). "MINING PLANET SEARCH DATA FOR BINARY STARS: THE ψ1 DRACONIS SYSTEM". The Astrophysical Journal 815: 62. arXiv:1511.01903. Bibcode 2015ApJ...815...62G. doi:10.1088/0004-637X/815/1/62.
  8. 8.0 8.1 Pasinetti Fracassini, L. E. et al. (2001). "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) – Third edition – Comments and statistics". Astronomy & Astrophysics 367 (2): 521–24. arXiv:astro-ph/0012289. Bibcode 2001A&A...367..521P. doi:10.1051/0004-6361:20000451.
  9. 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 Endl, Michael; Brugamyer, Erik J.; Cochran, William D.; MacQueen, Phillip J.; Robertson, Paul; Meschiari, Stefano; Ramirez, Ivan; Shetrone, Matthew et al. (2016). "Two New Long-Period Giant Planets from the Mcdonald Observatory Planet Search and Two Stars with Long-Period Radial Velocity Signals Related to Stellar Activity Cycles". The Astrophysical Journal 818: 34. arXiv:1512.02965. Bibcode 2016ApJ...818...34E. doi:10.3847/0004-637X/818/1/34.
  10. 10.0 10.1 Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  11. Lua error in Module:Citation/CS1 at line 876: attempt to call method 'sub' (a nil value).
  12. 12.0 12.1 Star Name – R.H. Allen p.212
  13. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  14. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  15. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 10 日
  16. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).

Add your comment
The Science Archives welcomes all comments. If you do not want to be anonymous, register or log in. It is free.

As a reminder, article comments are only for discussions on how to improve the article. Please direct other comments to a user's talk page. Please be formal and do not use excessive uppercase. Please be advised you may receive an automatic block if you break the article comments policy. For information regarding what is acceptable/not acceptable in article comments, please message Icons-flag-ru.png Joey (talk), Natalia (talk), Icons-flag-fr.png ynoss (talk), or Icons-flag-ca.png Daniel (older account/talk).