Current hash rate required for one block Now, the height of the blockchain is 485531. How much hash power is ideally required to mine block number 500000.

And how much hash rate does a node require to publish a block successfully each hour?
Firstly, new blocks are published every 10 minutes on average, not every hour. 

There is no 'required' amount of hash power to mine a block. It is all a game of luck, a race against the rest of the network. To mine a valid block roughly once per hour, you would be mining a sixth of the total blocks (~6 blocks mined per hour), so in theory you would need around a sixth of the total hashpower on the bitcoin network. You can see the current network hash rate here:
https://blockchain.info/charts/hash-rate

At the time of this post, that's roughly 1.4 exahashes per second (million terahashes per second).