58 Eridani

JPL, CalTech, NASA


Larger illustration


Astronomers have identified 58
Eridani as a prime target for the
Terrestrial Planet Finder (TPF),
now planned for launch between
2014 and 2020.

The Star

58 Eridani is a yellow-orange main sequence dwarf star of spectral and luminosity type G1-3 V. Similar to Sol (Giusa Cayrel de Strobel, 1996), this "Solar analogue" may have roughly the same mass, around 96 to 99 percent of its diameter (Pasinetti-Fracassini et al, 2001; Perrin and Karoji, 1987; and Johnson and Wright, 1983, page 655), and 96 percent of its luminosity. It appears to be around 97 percent as enriched than Sol in elements heavier than hydrogen ("metals") based on its abundance of iron (B.J. Taylor, 2003).

The star is considered to be a nearby, young Solar analogue -- with a spectral type from G0 to K2 and a coronal x-ray luminosity suggesting an age of less than 800 million years (Gaidos and Gonalez, 2002; and Eric J. Gaidos, 1998). Little 10-micron emission from silicate dust in a circumstellar disk around the star was found suggesting that 58 Eridani may be more than 400 million years old although significant excess infrared emission was detected (Gaidos and Koresko, 2003). The star has "a combination of differential rotation and concentration of starspot activity at different stellar latitudes from year to year" (Guidos et al, 2000, in pdf). Useful catalogue numbers and designations for the star include: 58 Eri, HR 1532, Gl 177, Hip 22263, HD 30495, BD-17 954, SAO 149888, and LTT 2088.

Hunt for Planetary Objects

An Earth-type planet with liquid water on its surface would require a stable orbit centered around 0.96 AU from 58 Eridani -- just under the orbital distance of Earth in the Solar System. Such a planet would have an orbital period lasting close to an Earth year. However, given its conjectured young age, an Earth-sized planet is not likely to have developed an oxygen-rich atmosphere but is likely to be under heavy bombardment by asteroids and comets. Astronomers are hoping to use NASA's Terrestrial Planet Finder (TPF) and the ESA's Darwin planned groups of observatories to search for a rocky inner planet in the so-called "habitable zone" (HZ) around 58 Eridani. As currently planned, the TPF will include two complementary observatory groups: a visible-light coronagraph to launch around 2014; and a "formation-flying" infrared interferometer to launch before 2020, while Darwin will launch a flotilla of three mid-infrared telescopes and a fourth communications hub beginning in 2015.