Hundreds of planets are known to orbit many times closer to their star than Mercury is to our sun, with some heated to greater than 1000 K. The planets may have formed much further from the star where material in the protoplanetary disc surrounding a nascent star was plentiful enough. The planets would have then migrated inward to their current location where we infer from extrapolated observations of star formation there is not enough material to form planets. Many fundamental aspects of planet migration are still being worked out