Iota Draconis b

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Iota Draconis b[1]
Artist's concept of Iota Draconis b (foreground) orbiting its parent star (center).
Discovered byFrink et al.
Discovery dateJanuary 8, 2002
Doppler Spectroscopy
Orbital characteristics
1.275 (± 0.074) AU
Eccentricity0.7124 (± 0.0039)
511.098 (± 0.089) d
1.4 y
2,452,014.59 (± 0.30)
91.58 (± 0.81)
Semi-amplitude307.6 (± 2.3)
StarIota Draconis
Physical characteristics
Mean radius
~12 R
Temperature598 K (325 °C; 617 °F)

Iota Draconis b, formally named Hypatia (pronounced /hˈpʃiə/ or /hɪˈpʃə/), 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.[2]


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.[3] The process involved public nomination and voting for the new names.[4] In December 2015, the IAU announced that the winning name for this planet was Hypatia.[5] 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.[6]


Mass, radius and temperature

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

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.[7] In comparison, the Sun is about 4.6 billion years old[8] and has a surface temperature of 5778 K.[9]

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.[2]


  1. ^ Butler, R. P.; 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/0607493. Bibcode:2006ApJ...646..505B. doi:10.1086/504701.
  2. ^ 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 doi:10.1086/341629.
  3. ^ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. 9 July 2014
  4. ^ NameExoWorlds The Process
  5. ^ Final Results of NameExoWorlds Public Vote Released, International Astronomical Union, 15 December 2015.
  6. ^ NameExoWorlds The Approved Names
  7. ^ Safonova, M.; Murthy, J.; Shchekinov, Yu. A. (2014). "Age Aspects of Habitability". International Journal of Astrobiology. 15 (2): 93–105. arXiv:1404.0641. Bibcode:2016IJAsB..15...93S. doi:10.1017/S1473550415000208.
  8. ^ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
  9. ^ Fraser Cain (September 15, 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.

External links

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