DEC. 27, 1571 –
NOV. 15, 1630
Kepler’s importance to astron-
omy is so great that the final
exam of my History of
Astronomy course at Ohio
State University consisted
of just one question: Given
Kepler’s laws of planetary motion, derive Newton’s
three laws. Indeed, German astronomer Johannes
Kepler’s laws — especially the first, which states
that planets move in ellipses (not circles) — set the
stage for the law of universal gravitation.
In addition to many years of arduous orbital cal-
culations, Kepler also observed a supernova, now
called Kepler’s Nova, in 1604. Noting that the object
showed no parallax, he concluded that it was neither
atmospheric nor nearby, but that its distance must be
the same as the other stars. PORTRAIT: AIP EMILIO SEGRÈ VISUAL ARCHIVESThe supernova that Johannes Kepler observed in 1604 is pictured here in
X-rays by NASA’s Chandra X-ray Observatory. The bright arc at the top is
caused by debris from the explosion plowing into surrounding gas and
dust. X-RAY: NASA/CXC/SAO/D.PATNAUDE, OPTICAL: DSS3
Johannes
Kepler
Nicolaus
Copernicus
FEB. 19, 1473 –
MAY 24, 1543
Unlike Herschel, who seems to have
done everything, Polish astrono-
mer Nicolaus Copernicus did just
one thing. Most scholars, however,
think it was the greatest thing ever
done in astronomy. Copernicus
formulated what’s now called the
heliocentric model — he moved Earth from the center of
the universe and replaced it with the Sun. And although he
outlined his theory around 1514, he didn’t publish his epic
De revolutionibus orbium coelestium (On the Revolutions
of the Heavenly Spheres) until he was on his deathbed in
1543, mainly because he was concerned with criticism, both
scientific and religious. PORTRAIT: ENGRAVING BY JEREMIAN FALCK, COURTESY AIP EMILIO SEGRÈ
VISUAL ARCHIVES4
NOV. 15, 1738 –
AUG. 25, 1822
You may know that Frederick
William Herschel discovered
Uranus in 1781. But Herschel
didn’t stop there. He discovered
four moons: Saturn’s Enceladus
and Mimas and Uranus’ Titania
and Oberon. He also established
the basis for the study of binary stars, and by revisiting
them for more than a quarter of a century showed that
they were physically related, not simply chance align-
ments. He found nearly 2,500 deep-sky objects and, as if
all this weren’t enough, discovered infrared radiation and
that the Sun is moving toward the constellation Hercules.
PORTRAIT: J. RUSSELL, COURTESY AIP EMILIO SEGRÈ VISUAL ARCHIVES, E. SCOTT BARR COLLECTION5
William Herschel
46 ASTRONOMY • FEBRUARY 2022