After graduating from the University of Valencia in 1537, he was educated in astronomy and mathematics by the mathematicians and professors Oronce Fine and Gemma Frisius.
A prominent and highly respected figure in Spanish mathematics and astronomy, he gained fame throughout Europe for his 1573 publication Libro del nuevo cometa, his account of SN 1572.
[2][5] At that time, the university officially lacked a mathematics professor, so Muñoz attended private lessons in astronomy and geometry delivered by Frisius in his own home.
[4][6] As a professor in both subjects, he was both well-paid and well-respected; those who selected Muñoz for the mathematics professorship called him "distinguished and eminent in all of the sciences".
[8][10] He was a major figure in Spanish mathematical circles and was considered an "expert" in the field by Gabriel Serrano, who succeeded him at the University of Salamanca.
His first, Institutiones Arithmeticae ad Percipiendam Astrologiam et Mathematicas facultates necessariae, was published in 1566 and covers essential arithmetic knowledge needed for astronomic calculations.
[2][13] The publication, which begins with a refutation of Aristotelian cosmology,[14] is Muñoz's account of SN 1572, which he observed on 2 December 1572 while still a professor at the University of Valencia.