When a sea star has only one arm remaining (and often a portion of the central disc), and it regrows all of its other arms, it's called a "comet" because the original arm is so much larger and appears similar to the tail of a true comet traveling across the sky.
Today Eric spotted another comet, but in a different species:
This is a Six-armed Sea Star (Leptasterias sp.). They normally have six arms of similar length, but in this case, the sea star has one very large arm and five much smaller arms. Note the larger (original) arm is pink, while the newer arms are white.
For comparison, here's a more typical Six-armed Sea Star:
Both of these sea stars were photographed in Del Norte County on 26 May 2017.
I wrote a little more about sea star "comets" in the August 2015 post, so if you're interested, you can review that post here.