Original: The moon was discovered by British astronomer William Lassell on October 10 , 1846 , just 17 days after Neptune itself was discovered by German astronomers Johann Gottfried Galle and Heinrich Louis d'Arrest .
Simplified: It was discovered by British astronomer William Lassell on October 10 1846 , just 17 days after Neptune itself was discovered by German astronomer Johann Gottfried Galle .