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Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus[1]
Right ascension 21h 38m 08.733s[2]
Declination +30° 29′ 19.47″[2]
Apparent magnitude (V) 10.54
Spectral type K
Proper motion (μ) RA: −78.0±0.9[2] mas/yr
Dec.: −125.5±1.0[2] mas/yr
Distance 90 ± 3 pc
Mass 0.857±0.039 M
Radius 0.837 R
Luminosity 0.48±0.04 L
Surface gravity (log g) 4.53±0.02[3] cgs
Temperature 5345±70[3] K
Metallicity 0.06±0.08[3]
Rotational velocity (v sin i) 1.3±1.0[3] km/s
Age 7.8±3.3 Gyr
Other designations
GSC 2717-00417

HAT-P-17 is a K-type main-sequence star about 90 ± 3 parsecs (293.5 ± 9.8 ly) away. It has a mass of about 0.857 ± 0.039 M. It is the host of two planets, HAT-P-17b and HAT-P-17c, both discovered in 2012.[4] A search for a binary companion star using adaptive optics at the MMT Observatory was negative.[5]

Planetary system[edit]

In 2012 a multi-planet system consisting of a transiting hot Saturn in an eccentric orbit and a Jupiter like planet in an outer orbit. The transiting planet HAT-P-17b was detected by the HATNet Project using telescopes located in Hawaii, Arizona and at Wise Observatory in Israel. It was confirmed with radial velocity measurements taken at the Keck telescope which also lead to the discovery of the second planet on a much wider orbit.[4]

The HAT-P-17 planetary system[4][6]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b 0.532+0.018
0.0882±0.0014 10.338523+0.000088
0.3422±0.0046 89.3+0.18
1.010±0.029 RJ
c > 3.4+1.1


  1. ^ Roman, Nancy G. (1987). "Identification of a Constellation From a Position". Publications of the Astronomical Society of the Pacific 99 (617): 695–699. Bibcode:1987PASP...99..695R. doi:10.1086/132034.  Vizier query form
  2. ^ a b c d Zacharias, N. et al. (2013). "The Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4)". The Astronomical Journal 145 (2). 44. arXiv:1212.6182. Bibcode:2013AJ....145...44Z. doi:10.1088/0004-6256/145/2/44. Vizier catalog entry
  3. ^ a b c d Torres, Guillermo et al. (2012). "Improved Spectroscopic Parameters for Transiting Planet Hosts". The Astrophysical Journal 757 (2). 161. arXiv:1208.1268. Bibcode:2012ApJ...757..161T. doi:10.1088/0004-637X/757/2/161. 
  4. ^ a b c Howard, A. W. et al. (2012). "HAT-P-17b,c: A Transiting, Eccentric, Hot Saturn and a Long-period, Cold Jupiter". The Astrophysical Journal 749 (2). 134. arXiv:1008.3898. Bibcode:2012ApJ...749..134H. doi:10.1088/0004-637X/749/2/134. 
  5. ^ Adams, E. R. et al. (2013). "Adaptive Optics Images. II. 12 Kepler Objects of Interest and 15 Confirmed Transiting Planets". The Astronomical Journal 146 (1). 9. arXiv:1305.6548. Bibcode:2013AJ....146....9A. doi:10.1088/0004-6256/146/1/9. 
  6. ^ Fulton, Benjamin J. et al. (2013). "The Stellar Obliquity and the Long-period Planet in the HAT-P-17 Exoplanetary System". The Astrophysical Journal 772 (2). 80. arXiv:1301.6289. Bibcode:2013ApJ...772...80F. doi:10.1088/0004-637X/772/2/80. 

Coordinates: Sky map 21h 38m 09s, +30° 29′ 19″