Iota Draconis b

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Iota Draconis b[1]
Exoplanet List of exoplanets
Artist's concept of Iota Draconis b (foreground) orbiting its parent star (center).
Parent star
Star Iota Draconis
Constellation Draco
Right ascension (α) 15h 24m 55.7747s
Declination (δ) +58° 57′ 57.836″
Apparent magnitude (mV) 3.29
Distance 101.2 ly
(31 pc)
Spectral type K2III[2]
Mass (m) 1.82 (± 0.23)[2] M
Radius (r) 11.99 (± 0.06)[2] R
Temperature (T) 4545 (± 110)[2] K
Metallicity [Fe/H] 0.14[2]
Age 10.015[3] Gyr
Physical characteristics
Minimum mass (m sin i) 8.82 (± 0.72) MJ
Radius (r) ~12 R
Stellar flux (F) 34.3
Temperature (T) 598 K (325 °C; 617 °F)
Orbital elements
Semi-major axis (a) 1.275 (± 0.074) AU
Eccentricity (e) 0.7124 (± 0.0039)
Orbital period (P) 511.098 (± 0.089) d
(1.4 y)
Argument of
(ω) 91.58 (± 0.81)°
Time of periastron (T0) 2,452,014.59 (± 0.30) JD
Semi-amplitude (K) 307.6 (± 2.3) m/s
Discovery information
Discovery date January 8, 2002
Discoverer(s) Frink et al.
Discovery method Doppler Spectroscopy
Discovery status Confirmed
Other designations
Hypatia, HD 137759 b, HIP 75458 b
Database references
Extrasolar Planets
Exoplanet Archive data
Open Exoplanet Catalogue data

Iota Draconis b, also named Hypatia, is an exoplanet orbiting the K-type giant star Iota Draconis about 101.2 light-years (31 parsecs, or nearly 2.932×1014 km) from Earth in the constellation Draco. The exoplanet was found by using the radial velocity method, from radial-velocity measurements via observation of Doppler shifts in the spectrum of the planet's parent star. It was the first planet discovered orbiting a giant star.[4]

Following its discovery the planet was designated Iota Draconis b. In July 2014 the International Astronomical Union launched a process for giving proper names to certain exoplanets and their host stars.[5] The process involved public nomination and voting for the new names.[6] In December 2015, the IAU announced that the winning name for this planet was Hypatia.[7] The winning name was submitted by Hypatia, a student society of the Physics Faculty of the Universidad Complutense de Madrid, Spain. Hypatia was a famous Greek astronomer, mathematician, and philosopher.[8]


Mass, radius and temperature[edit]

Iota Draconis b is a "super-Jupiter" a planet that has a radius and mass larger than that of the gas giants Jupiter and Saturn. It has a temperature of 598 K (325 °C; 617 °F). It has an estimated mass of around 8.82 MJ and a potential radius of around 12 R based on its mass, since it is more massive than Jupiter.

Host star[edit]

The planet orbits a (K-type) giant star named Iota Draconis. The star has exhausted the hydrogen supply in its core and is currently fusing helium. The star has a mass of 1.82 M and a radius of around 12 R. It has a surface temperature of 4545 K and is about 10 billion years old based on its evolution.[3] In comparison, the Sun is about 4.6 billion years old[9] and has a surface temperature of 5778 K.[10]

The star's apparent magnitude, a measure of how bright it appears from Earth, is 3.31. Therefore, Iota Draconis can be seen with the naked eye.


Iota Draconis b orbits its star with nearly 55 times the Sun's luminosity (55 L) every 511 days at a maximum distance of 1.275 AU (compared to Mars' orbital distance from the Sun, which is 1.52 AU) It has a very eccentric orbit, with an eccentricity of 0.7124.


Discovered in 2002 during a radial velocity study of K-class giant stars, its eccentric orbit aided its detection, as giant stars have pulsations which can mimic the presence of a planet.[4]


  1. ^ Butler; Wright, J. T.; Marcy, G. W.; Fischer, D. A.; Vogt, S. S.; Tinney, C. G.; Jones, H. R. A.; Carter, B. D.; et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal. 646 (1): 505–522. arXiv:astro-ph/0607493Freely accessible. Bibcode:2006ApJ...646..505B. doi:10.1086/504701. 
  2. ^ a b c d e Baines, Ellyn K.; et al. (December 2011), "Fundamental Parameters of the Exoplanet Host K Giant Star ι Draconis from the CHARA Array", The Astrophysical Journal, 743 (2): 130, arXiv:1109.4950Freely accessible, Bibcode:2011ApJ...743..130B, doi:10.1088/0004-637X/743/2/130 
  3. ^ a b Safonova, M.; Murthy, J.; Shchekinov, Yu. A. (2014). "Age Aspects of Habitability". International Journal of Astrobiology. 15 (2): 93–105. arXiv:1404.0641Freely accessible. doi:10.1017/S1473550415000208. 
  4. ^ a b Frink; Mitchell, David S.; Quirrenbach, Andreas; Fischer, Debra A.; Marcy, Geoffrey W.; Butler, R. Paul (2002). "Discovery of a Substellar Companion to the K2 III Giant Iota Draconis". The Astrophysical Journal. 576 (1): 478–484. Bibcode:2002ApJ...576..478F. doi:10.1086/341629. 
  5. ^ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. 9 July 2014
  6. ^ NameExoWorlds The Process
  7. ^ Final Results of NameExoWorlds Public Vote Released, International Astronomical Union, 15 December 2015.
  8. ^ NameExoWorlds The Approved Names
  9. ^ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011. 
  10. ^ Fraser Cain (September 15, 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011. 

External links[edit]

Coordinates: Sky map 15h 24m 55.7747s, +58° 57′ 57.836″