The four examples of K stars (above) show that Epsilon Eridani exhibits much higher intrinsic noise than other K stars. Thus, the possible planet around Epsilon Eridani, first suggested by Bruce Campbell in 1987, remains controversial. In August 2000, Hatzes et al. revived interest in the planet interpretation.
However, the noise in the Doppler measurements, caused by the erratic photosphere and the strong magnetic field variations, renders the existence of the planet uncertain. Our knowledge of the Doppler "jitter" of such highly magnetic stars is poor. The atmosphere itself could be varying with a 7 year period. However, the chromosphere shows no such period.
Campbell et al. detected a Doppler period of 10 yr and independently Cumming et al. found 6.9 yr. The modest agreement between these two periods and the large scatter of the Doppler measurements highlights the uncertainty in the planet interpretation.