And the fourth angel sounded, and the third part of the sun was smitten, and the third part of the moon, and the third part of the stars; so as the third part of them was darkened, and the day shined not for a third part of it, and the night likewise.
All Commentaries on Revelation 8:12 Go To Revelation 8
George Leo Haydock
The third part of the sun was smitten. This may signify a third part of men killed in those wars, or (according to the opinion that refers all to antichrist's time) that in those days the sun and moon shall not give above a third part of their light. (Witham)
Here we behold a noble figure of the Church, which whilst in its most flourishing state, like the sun, is suddenly obscured, and a third part extinguished by the heresy and schism of the Greeks, under Photius, which began in 866, and infected all orders of Christians, clergy and laity, princes and individuals, signified by the sun, moon, and stars. (Pastorini)