"...the moon" is known to be direct object. The direct object is known to be the noun or noun phrase which the subject acts upon. This means that the direct object is receiving the action from the subject.
In the given sentence, "The cow..." is the subject, "...jumped over..." is the action/verb while "...the moon" is the direct object.
The basic construction in identifying a direct object works like this: <em>Subject + Verb + Who or What.</em>
