The sunflower sea star (Pycnopodia helianthoides) is a large predatory sea star usually with 1624 limbs called rays. It is the largest sea star in the world. Sunflower sea stars can grow to have an arm span of 1 meter (3 ft 3 in) in diameter.[2] The color of the sunflower sea star ranges from bright orange, yellow and red to brown and sometimes to purple, with soft, velvet-textured bodies and 1624 arms with powerful suckers.[2][3] Most sea star species have a mesh-like skeleton that protects their internal organs.[4] Easily stressed by predators such as large fish and other sea stars, they can shed arms to escape, which will grow back within a few weeks. They are preyed upon by the king crab.[4]
I'm 98% certain of the species ID but have not had it confirmed by an expert. There are 180 species of Echinoderms in the Pacific Northwest, but this one seems pretty unique in the descriptions (largest seastar in the PNW; 16-24 arms -- this specimen appears to have 16), and matches the pictures of it online.
The animal is so flaccid that if its body is held long in the air, rays will break off and fall, as has happened to this specimen just above my hand. Photo by Dave Cowles, July 1997
Besides the large spines and pedicellariae on the aboral side, this seastar has long tube feet on the oral side. Note that this individual has been recently feeding, as indicated by the partly everted stomach. Photo by Dave Cowles at San Simeon, CA, April 1997 This seastar can move extremely rapidly for a seastar. Its presence elicits an escape reaction from many species such as the spiny scallop Chlamys hastata (click here for an .MPG movie), the sea cucumber Parastichopus californicus, and limpets. This movie shows how fast the animal is able to move its long tube feet.
This species is usually found subtidally but can sometimes be found in the very low intertidal or in cave tidepools, as this one was. Note the purple color.