ٱلنَّجْمُ ٱلثَّاقِبُ
Sentence structure
ٱلنَّجْمُ explains ٱلطَّارِقُ in the preceding question. ٱلثَّاقِبُ is its matching nominative adjective.
Ayah summary
At-Tariq is an intensely shining star.
ٱلنَّجْمُ — (It is) the star
Grammar: ٱل is the definite article; نَّجْمُ is nominative and explains ٱلطَّارِقُ as an apposition, adjective-like explanation, or predicate of an understood topic.
ٱلثَّاقِبُ — the piercing
Grammar: ٱل is the definite article; ثَّاقِبُ is a nominative active-participle adjective matching ٱلنَّجْمُ.