Iota Draconis b

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
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
Distance101.2 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 0.8[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 Archivedata
Open Exoplanet Cataloguedata

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 mass larger than that of the gas giants Jupiter and Saturn. It has a blackbody 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 around 800 million years old based on its evolution. Although much younger than the Sun, the higher mass of this star correlates to a faster evolution, leading to the host star having already departed from the main sequence. When on the main sequence, Iota Draconis was probably a Class A star with surface temperature between 7,400-10,000K.[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 an average 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. Bibcode:2016IJAsB..15...93S. 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. CiteSeerX accessible. 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″