As a retired physicist and astronomy hobbyist, I read with interest about the astronomical reference in "Killing Jesus: A History" by Bill O'Reilly and Martin Dugard ("Book review: 'Killing Jesus,'" Commentary, Sept. 26). The date of 5 B.C. in the month of March is specifically mentioned in the book as the time frame of Jesus' birth.
In a footnote on page 15, the authors speculate that in the hours before dawn on that date, a comet located in the constellation of Capricorn may have served as the Star of Bethlehem. Using astronomy software that I own, it is possible to determine the appearance of the stars from any point on Earth for any historical date and time. For the date in question, the constellation of Capricorn would have been seen to be located in the southeastern sky at 4 a.m. from the skies of Persia (from which the Magi are thought to have traveled). The constellation would have been positioned even farther to the East at earlier hours.
Since the Magi would have been traveling to the West in order to reach Bethlehem, a comet located in the southeastern sky could not possibly have served the purpose of a guiding light.
JEAN C. PIQUETTE