There is no mantra greater than Gayatri – There are four Vedas. Earlier the Vedas, were in the form of hymns (छन्दोमय) and in prose (गद्यमय) and existed as one whole. Later Veda Vyasa divided them into four Vedas. And so, he was known by the name Vyasa.
The Sun occupies the central position in the Solar System. He occupies the central position in the Navagraha System too. Even as he is rising, the demonic forces conjure to attack him and so the ‘Dwijas’ chant the Gayatri mantra and offer ‘Arghya’ (अर्घ्य) by which the demonic forces are contained
The main deity of the Brahmadarsana is Gayatri. Gayatri is the Mother of Vedas- Vedamata. Brahma the creator is closely connected with Gayathri mantra. Any mantra can be used as ashtra also.