How many arms can a sea star have?

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A common comet star and a cushion sea star rest on colorful sponges and seagrass in a vibrant Caribbean underwater scene. — echinoderm Starfishes.

While sea stars are often associated with having five arms, the number of rays varies significantly across different species within the phylum Echinodermata.

Typical count: Most sea star species possess five arms.1
Variations: Many species feature a higher number of rays. For example, the spiny sun star (Crossaster papposus) can have up to 15 arms, while the sunflower sea star (Pycnopodia helianthoides) typically has between 15 and 24.1
Maximum range: Some genera exhibit even greater numbers; the genus Heliaster may have as many as 50 arms.1

Additionally, sea stars have the biological capability to lose one or more arms and regenerate new ones.1