On this day in 1814 - September 27th - American astronomer Daniel Kirkwood was born.
Kirkwood is best known for his study of asteroid orbits. When arranging the then-growing number of discovered asteroids by their distance from the Sun, he noted several gaps, now named Kirkwood gaps. He associated these gaps with orbital resonances with the orbit of Jupiter.
On this day in 1880 - September 30th - Henry Draper took the first photograph of the Orion Nebula.
Draper was an American physician, professor of medicine, keen astronomer and pioneer of astrophotographer. Stars with HD numbers are listed in the Henry Draper Catalog compiled by Harvard College Observatory and funded by Draper's widow, Anna Draper.
On this day in 1920 - October 2nd - Italian mathematician and engineer Giuseppe 'Bepi' Colombo was born.
Colombo, known as "Grandfather of the fly-by", suggested to NASA in 1970 that its Mariner 10 mission could achieve a second fly-by of Mercury by making use of the planet's gravity. A careful analysis showed this could indeed be done and was incorporated into the mission. ESA (European Space Agency) has commemorated him by naming its Mercury mission BepiColombo.
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