Epsilon Eridani - Properties

Properties

At a distance of 10.50 ly (3.22 parsecs), Epsilon Eridani is the 13th nearest known star (and ninth nearest solitary star or stellar system) to the Sun as of 2011. The proximity of this star makes it one of the most studied stars of its stellar classification. This star is located in the northern part of the constellation Eridanus, about 3° east of the slightly brighter star Delta Eridani. With a declination of −9.46°, Epsilon Eridani can be viewed from much of the Earth's surface. Only to the north of latitude 80° N is it permanently hidden below the horizon. The apparent magnitude of 3.73 can make this star difficult to observe from an urban area with the unaided eye, as the night skies over cities are obscured by light pollution.

Epsilon Eridani has an estimated 82% of the Sun's mass and 74% of the Sun's radius, but only 34% of its luminosity. The estimated surface temperature is 5,084 K. With a stellar classification of K2 V, it is the second-nearest K-type main-sequence star after Alpha Centauri B. Indeed, since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. Its metallicity, or enrichment in elements heavier than helium, is slightly lower than the Sun's. In the star's chromosphere, a region of the outer atmosphere just above the light emitting photosphere, the proportion of iron is estimated at 74% of the Sun's abundance.

The K-type classification of this star indicates that the spectrum displays relatively weak absorption lines from energy absorbed by hydrogen, plus strong lines of neutral atoms and singly ionized calcium (Ca II). The luminosity class V is assigned to stars that are undergoing thermonuclear fusion of hydrogen at their core. For a K-type main-sequence star, this fusion is dominated by the proton–proton chain reaction, wherein a series of mergers of four hydrogen nuclei results in a helium nucleus. In the inner region of this star, energy is transported outward from the core by means of radiation, which results in no net motion of the surrounding plasma. Outside of this region, in the star's envelope, energy is carried to the photosphere by plasma convection, where it radiates into space.