Eta Eridani
A red clump giant in Eridanus, also known as Azha.
Eta Eridani, also designated η Eridani and officially named Azha (the 'h' is silent), is a giant star located in the constellation Eridanus. Parallax data from the Hipparcos mission places it roughly 137 light-years from the Sun.
The star's Bayer designation is η Eridani, Latinised as Eta Eridani. Its traditional name, Azha, comes from the old Arab asterism udḥiyy al-naʽām, meaning "the ostrich nest" or "hatching place," which included this star. In medieval manuscripts, the first word was miscopied from ادحى to ازحى, which could be read as azḥā. The International Astronomical Union's Working Group on Star Names approved Azha as the official name on 12 September 2016, and it now appears on the IAU's list of approved star names.
In Chinese astronomy, Eta Eridani is part of an asterism called Celestial Meadows, which also includes Gamma, Pi, Delta, Epsilon, Zeta Eridani, Pi Ceti, and Tau1 through Tau9 Eridani. The Chinese name for Eta Eridani itself is derived from this grouping.
Eta Eridani is a K3 giant star, an evolved object that has expanded to tens of times the Sun's diameter and shines with nearly sixty times its luminosity. It is a red clump giant, slightly more massive than the Sun, and is currently fusing helium in its core. The star is also a mild barium star, sometimes called a "semi-barium" star. While most barium stars have binary companions, Eta Eridani has no known companion.
This star exhibits high proper motion, moving across the sky at a rapid rate for a relatively nearby star. It is suspected to be variable, with brightness fluctuating between magnitudes 3.81 and 3.90.
Quick Facts
- Bayer designation
- η Eridani
- Official name
- Azha
- Distance
- approximately 137 light-years
- Spectral class
- K3
- Luminosity class
- giant
- Apparent magnitude range
- 3.81 to 3.90 (suspected variable)
- Proper motion
- high proper motion star
Facts from the source article.
Lore & Background
The star bore the traditional name Azha, from the old Arab asterism نَعَام أُدْحِيّ udḥiyy al-naʽām 'the ostrich nest' (or 'hatching place'), which included Eta Eridani. The first word, ادحى udḥiyy, was miscopied as ازحى (readable as azḥā) in medieval manuscripts. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Azha for this star on 12 September 2016 and it is now so included in the List of IAU-approved Star Names. In Chinese, the asterism known as Celestial Meadows consists of Eta Eridani, Gamma Eridani, Pi Eridani, Delta Eridani, Epsilon Eridani, Zeta Eridani, Pi Ceti, Tau1 Eridani, Tau2 Eridani, Tau3 Eridani, Tau4 Eridani, Tau5 Eridani, Tau6 Eridani, Tau7 Eridani, Tau8 Eridani and Tau9 Eridani. Consequently, the Chinese name for Eta Eridani itself is derived from that asterism.
Reader's Guide
Eta Eridani is significant as a red clump giant, a star slightly more massive than the Sun that is currently fusing helium in its core. It is an evolved star that has expanded to tens of times the size of the Sun and nearly sixty times its luminosity. It is classified as a mild barium star, sometimes referred to as a 'semi-barium' star. Although most barium stars are in binary systems, Eta Eridani has no known companion. The star is also a high proper motion star, moving across the sky at a high rate compared to most stars. It is suspected to be a variable star with a range from magnitude 3.81 to 3.90. Its traditional name Azha, approved by the IAU in 2016, preserves a medieval miscopying of an Arabic term for an ostrich nest, linking the star to ancient Arab astronomical traditions. The star's inclusion in the Chinese asterism Celestial Meadows further illustrates its role in multiple cultural sky traditions.
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