A 44-byte header cointaining:
- magic: 0xfa, 0xbe, 'm', 'm' (only required if over 20 bytes past the start of the script; optional otherwise)
- block_hash: Hash of the Namecoin block header
- merkle_size: Number of entries in aux work merkle tree.
- merkle_nonce: Nonce used to calculate indexes into aux work merkle tree; you may as well leave this at zero
is included in the scriptSig of the coinbase transaction in the Bitcoin block and sent to the Bitcoin network. Note that it is only sent to the Bitcoin network if it meets the network difficulty of Bitcoin. If it only meets the difficulty of Namecoin, it is only sent to the Namecoin network.