Iota Capricorni Explained

Iota Capricorni (ι Cap, ι Capricorni) is a solitary, yellow-hued star in the southern constellation of Capricornus. It can be seen with the naked eye, having an apparent visual magnitude of +4.3. Based upon an annual parallax shift of 16.2 mas as seen from the Earth, the star is located about 201 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.08 due to interstellar dust.

This is an evolved G-type giant star with a stellar classification of G8 III. It is classified as a BY Draconis type variable star. This is a chromospherically-active star with a longitudinal magnetic field strength of and an X-ray luminosity of . The activity and photometric variation of the star allow an estimate of its rotation period as 68 days.

Iota Capricorni has an estimated 2.9 times the mass of the Sun and nearly 11 times the Solar radius. It is 390 million years old and is radiating 83 times the solar luminosity from its chromosphere at an effective temperature of 5,200 K.

Chinese name

In Chinese, Chinese: 十二國 (Chinese: Shíer Guó), meaning Twelve States, refers to an asterism which represents twelve ancient states in the Spring and Autumn period and the Warring States period, consisting of ι Capricorni, φ Capricorni, 38 Capricorni, 35 Capricorni, 36 Capricorni, χ Capricorni, θ Capricorni, 30 Capricorni, 33 Capricorni, ζ Capricorni, 19 Capricorni, 26 Capricorni, 27 Capricorni, 20 Capricorni, η Capricorni and 21 Capricorni.[1] Consequently, the Chinese name for ι Capricorni itself is Chinese: 代一 (Chinese: Dài yī, English: the First Star of Dai), meaning that this star (together with 37 Capricorni[2]) represents the state Dai (or Tae)(Chinese: ).[3]

Planetary system

In 2022, two exoplanets, both super-Jovian in mass, were discovered in orbit around Iota Capricorni using a combination of radial velocity and astrometry. The inner planet has a highly eccentric orbit.

Notes and References

  1. 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, .
  2. http://www.ianridpath.com/startales/capricornus.htm Iad Ridpath's Startales - Capricornus the Sea Goat
  3. AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 4 日