Final answer:
Yes, 'undeniably' can be placed between dashes in the given sentence to add emphasis and is both grammatically correct and stylistically effective.
Step-by-step explanation:
The question asks if the word undeniably can be correctly placed within dash lines in the sentence provided. In English, dashes can be used to add emphasis or to insert a parenthetical element into a sentence.
In the example given, placing 'undeniably' between dashes would emphasize the speaker's conviction that the addressee is the brightest star among all. This usage is both grammatically correct and stylistically effective, as it adds dramatic effect to the statement.
Examples of similar usage can be found in various forms of writing, including poetry and prose, where the placement of a word within dashes serves to underscore the importance or certainty of the surrounding phrase.