A rogue planet is one that has been knocked out of its orbit by something or other. Losing their star system changes everything for that planet. A rogue planet traveling through space by itself may have a substantial history, and possibly even life! Kurzgesagt explains how that theoretically might happen.
there are more stars in the solar system than there are atoms in the entire universe
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Oops, that's an impossibility. Our solar system has but one star, Sol (though there just might be a dim companion out there). Are you thinking of a galaxy, maybe? But every star comprises a gazillion atoms. Maybe you meant to word that a tad differently.
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