On this day in 1631 - November 7th - French priest and astronomer Pierre Gassendi observed a transit of Mercury.
Johannes Kepler had predicted transits of Mercury and Venus, but when Gassendi witnessed a transit of Mercury, he was the first person to see such a transit. There was a transit of Mercury in November 2019, but the next one doesn't occur until November 13, 2032.
On this day in 1934 - November 9th - American astronomer Carl Sagan was born.
Sagan was also noted as a science writer and communicator, and is still remembered for his television series Cosmos. In 2009 Carl Sagan Day was initiated as an annual celebration of astronomy and of Sagan's ideals.
On this day in 1875 - November 11th - American astronomer Vesto Slipher was born.
Slipher was director of the Lowell Observatory in Arizona, and the first to discover the redshift of galaxies when he obtained their spectra and measured their radial velocities. This laid the foundation for the work that Edwin Hubble's work on the expansion of the Universe.
On this day in 1891 - November 12th - American astronomer Seth Barnes Nicholson was born.
Nicholson worked at Mount Wilson Observatory in California for over 40 yrs, mainly concerned with solar activity. But he also computed the orbit of several comets, discovered a Trojan asteroid, and is probably best remembered for his discovery of four satellites of Jupiter.
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