Starfish, or more accurately sea stars, fill a niche as predator and prey in marine ecosystems close to shore. With more than 18,000 species in the world, they range from the tropics to the Pacific Northwest and further north. They can grow larger than a foot across and can have as many as 40 arms. While sea stars are known for their ability to regrow lost arms, they have an unusual digestive system, too.
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Scientists are perhaps some of the smart few that make up the human population and are never short on knowledge. They research and discover and conduct tests to gain more knowledge, but the answer to your question is stars are huge celestial bodies made mostly of hydrogen and helium that produce light and heat from the churning nuclear forges inside their cores, and scientist know this because of their research.
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Although protons resemble other positive ions such as Na+ and K+ in their movement across membranes, in some respects they are unique. Hydrogen atoms are by far the most abundant type of atom in living organisms; they are plentiful not only in all carbon-containing biological molecules, but also in the water molecules that surround them. The protons in water are highly mobile, flickering through the hydrogen-bonded network of water molecules by rapidly dissociating from one water molecule to associate with its neighbor, Protons are thought to move across a protein pump embedded in a lipid bilayer in a similar way: they transfer from one amino acid side chain to another, following a special channel through the protein.
