You cannot do this with the default Search component without modifying the search plugin database query. This is considered a core hack, therefore not recommended.
Instead I'd suggest using Smart Search:
- Go to Plugins >> Smart Search, then enable it.
- Go to Modules >> Smart Search. Enable and assign to a page.
- Go to Components >> Smart Search >> Index.
Now that the initial steps are done, you should create a Template Override for the following file:
Once done, open the template override file:
In here, you need to add the following code which will display the author:
<?php echo $this->result->author; ?>
Hope this helps