天苑四
In an alternative scenario, the exozodiacal dust may be generated in an outer belt that is orbiting between 55 and 90 AU from Epsilon Eridani and has an assumed mass of 10−3 times the mass of Earth. This dust is then transported inward past the orbit of Epsilon Eridani b. When collisions between the dust grains are taken into account, the dust will reproduce the observed infrared spectrum and brightness. Outside the radius of ice sublimation, located beyond 10 AU from Epsilon Eridani where the temperatures fall below 100 K, the best fit to the observations occurs when a mix of ice and silicate dust is assumed. Inside this radius, the dust must consist of silicate grains that lack volatiles.