Galileo Galilei
FEB. 15, 1564 – JAN. 8, 1642
As I stood in the science museum of
Florence (now known as Museo Galileo)
gazing at the first lens Galileo made,
Astronomy Editor David Eicher, standing
next to me, said, “That’s where optical
astronomy began.” For that reason, Italian
astronomer Galileo di Vincenzo Bonaiuti
de’ Galilei ranks No. 1 on this list.
Although he didn’t invent the telescope, Galileo was the first to
use it to study the sky. He observed sunspots, the phases of Venus,
Saturn’s rings (although he called them “handles”), and the four
large moons of Jupiter. He also saw stars fainter than the eye could
see, describing them with a term never before used: 7th magnitude.
And that’s my list. Discuss. Debate. Rearrange. Just don’t try to
change my mind. PORTRAIT: PAINTING BY JUSTUS SUSTERMANS, COURTESY AIP EMILIO SEGRÈ VISUAL ARCHIVES,
W.F. MEGGERS COLLECTION1
ABOVE: The objective lens that Galileo Galilei used for many of his observations
in 1609–1610 is preserved in an ebony and ivory frame in the Museo Galileo in
Florence. MUSEO GALILEOTycho Brahe
DEC. 14, 1546 – OCT. 24, 1601
Danish astronomer Tyge (Tycho) Ottesen Brahe
was history’s greatest pre-telescopic observer. In
fact, his careful observations of Mars enabled
Kepler to derive his laws of planetary motion.
Although Brahe didn’t have a telescope, he con-
structed many observing instruments: several
quadrants, an armillary sphere, a sextant, and
a large globe.
Two of his famous observations were of the
supernova that appeared in 1572 (now called
Tycho’s Nova) and the Great Comet of 1577. When
he measured their positions, he saw no parallax,
meaning that their distances placed them beyond
the Moon.2
As seen in this engraving, noble ancestors of Tycho Brahe
included Rosenkrans and Guldensteren, which has led some
scholars to suggest that Shakespeare was rejecting Tycho’s
geocentric theories when he killed off Rosencrantz and
Guildenstern in Hamlet. SARAH CAMPBELL BLAFFER FOUNDATION, HOUSTONMichael E. Bakich is a contributing editor of
Astronomy. Contrary to popular belief, he did not know
Eratosthenes.