Seems to me that Delta Vega was a moon of Vulcan or perhaps a moon of Vulcan's twin planet as Spock got a "front row seat" to the destruction, according to the mind meld.
Uhura:
'Mr. Spock.... Why don't you tell me what your homeworld looks like on a lovely night when the moon is full?'
Spock:
'Vulcan has no moon.'