Epsilon Andromedae

Lore & Background

Epsilon Andromedae is an evolved G-type giant star, believed to be a red clump star fusing helium in its core. It has approximately the same mass as the Sun but has expanded to nine times the Sun's radius, radiating 51 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,082 K. The suffix notation in its stellar classification indicates a strong underabundance of iron and an overabundance of cyanogen (CN) in its spectrum.

Based on an annual parallax shift of 19.2 mas, the star is located about 169 light years from the Sun. Its orbit in the Milky Way is highly eccentric, causing it to move rapidly relative to the Sun and neighboring stars. The system is moving closer to the Sun with a radial velocity of −84 km/s.

In Chinese astronomy, Epsilon Andromedae is part of an asterism called Legs, which includes several other stars in Andromeda and Pisces. Its Chinese name is derived from this asterism.

Reader's Guide

Epsilon Andromedae holds significance as a red clump star, a stage of stellar evolution where helium fusion occurs in the core, providing insight into the later life cycles of Sun-like stars. Its unusual chemical abundances—a strong underabundance of iron and an overabundance of cyanogen—make it a subject of interest for studies of stellar nucleosynthesis and galactic chemical evolution. The star's highly eccentric orbit and high radial velocity relative to the Sun suggest it may have originated from a different region of the Milky Way, offering clues about the dynamics of stellar populations. As a naked-eye object at magnitude 4.4, it has been cataloged in multiple star catalogs, including the Henry Draper Catalogue (HD 3546) and the Bonner Durchmusterung (BD+28 0103). Its Bayer designation, Epsilon Andromedae, places it within the classical naming system for stars in the constellation Andromeda. The star's legacy lies in its role as a benchmark for understanding giant star evolution, chemical peculiarities, and the kinematics of stars on eccentric galactic orbits.