 The winning names were submitted to the International Astronomical Union.However, 'Vulcan' was unacceptable to the IAU because it was not the name of an underworld deity and had already been used for a hypothetical planet inside the orbit of Mercury, as well as having given its name to the hypothetical vulcanoids.Cerberus is already the name of an asteroid, 1865 Cerberus, but the Greek form of the name, Kerberos, was acceptable to the IAU.