"Inner Core"@en . "Inner core"@en . . . "The inner core of the Earth, its innermost hottest part as detected by seismological studies, is a primarily solid sphere about km ( mi) in radius, only about 70% that of the Moon. It is believed to consist of an iron-nickel alloy, and may have a temperature similar to the Sun's surface."@en . . . . "The inner core of the Earth, its innermost hottest part as detected by seismological studies, is a primarily solid sphere about km ( mi) in radius, only about 70% that of the Moon. It is believed to consist of an iron-nickel alloy, and may have a temperature similar to the Sun's surface."@en . .