The Buruj are the giant stars, as Allah says,

[تَبَارَكَ الَّذِى جَعَلَ فِى السَّمَآءِ بُرُوجاً وَجَعَلَ فِيهَا سِرَاجاً وَقَمَراً مُّنِيراً ]

(Blessed is He Who has placed in the heaven Buruj, and has placed therein a great lamp (the sun), and a moon giving light.) (25:61) Ibn `Abbas, Mujahid, Ad-Dahhak, Al-Hasan, Qatadah and As-Suddi, all said, "Al-Buruj are the stars.'' Al-Minhal bin `Amr said,

[وَالسَّمَآءِ ذَاتِ الْبُرُوجِ ]

(By the heaven holding the Buruj.) "The beautiful creation.'' Ibn Jarir chose the view that it means the positions of the sun and the moon, which are twelve Buruj. The sun travels through each one of these "Burj'' (singular of Buruj) in one month. The moon travels through each one of these Burj in two-and-a-third days, which makes a total of twenty-eight positions, and it is hidden for two nights.