After studying physics at the Masaryk University in Brno and astronomy at the Charles University in Prague he joined the Astronomical Institute of the Academy of Sciences, Department of Stellar Astronomy in Ondřejov. Twenty years later he moved to the Institute of Physics, Low Temperature Physics Department at Řež, where he remained for more than ten years. Shortly after the Velvet Revolution he joined the High Energy Physics Department at the same institution. From 1992 to 1998, Grygar chaired the Czech Astronomical Society. He also chaired the Czech Television Council and the Science and Philosophy section of the European Culture Club. He is member of editorial boards of the periodicals Říše hvězd, Vesmír, Universum and Omega.
Dr. Grygar holds a Ph.D. in astrophysics. His papers focus on interplanetary matter (meteors, comets), limb darkening in stellar atmospheres, close binaries, novae, chemically peculiar stars and remote sensing.
He is well known to the public in the Czech Republic and Slovakia because of his famous TV series about the Universe - Okna vesmíru dokořán ("Wide open windows of the Universe"; 1982–1990). He also engages in activities against un-scientific charlatanism (in the Sisyfos Club of Skeptics).
In 2009, Dr. Grygar was awarded one of the most prestigious Czech scientific awards, Česká hlava.
In 2010, he was the inaugural recipient of the respectable Mensa Czech Republic Award.
Dr. Grygar is a recipient of a number of other awards.