|Robert Trumpler born. The astronomer established the existence of interstellar reddening by dust and made systematic observations of open star clusters.
|Riccardo Giacconi born. An astronomer who was one of the pioneers of X-ray astronomy and space astronomy. He won the Nobel Prize for Physics in 2002.
|The Russian Luna 3 spacecraft takes the first photos of the far side of the Moon.
|Ejnar Hertzsprung born. He was co-developer of the Hertzsprung-Russell Diagram which helps astronomers understand the life sequence of stars.
|Karl Schwarzschild born. An astronomer and physicist who applied Einstein’s equations of General Relativity to predict the simplest kind of black hole.
|English astronomer William Lassell discovered Neptune’s largest moon, Triton. It is the only major moon in our solar system to have a retrograde orbit – that is, it revolves around the Sun in a direction opposite to the rotation of the planet on its axis.
|Heinrich Olbers, born. He was an astronomer and doctor who discovered asteroids and comets, devised a new method of orbit calculation, and proposed the paradox named after him relating to the problem of why the sky is dark at night: If the universe is endless and uniformly populated with luminous stars, then every line of sight must eventually terminate at the surface of a star.
|Jesse Greenstein born. He contributed to many fields of astronomy, including the understanding of white dwarfs, star clusters and quasars, the abundances of the elements, and the interstellar medium and its components.
|Subrahmanyan Chandrasekhar born. He was a theoretical physicist who did crucial theoretical work on the lives and deaths of stars. He shared the Nobel Prize for Physics with William A Fowler in 1983 for their work in this field.
|The Yerkes Observatory in America – the site of the largest refractor telescope in the world -was formally dedicated. There was a meeting of the country’s astronomers during the days before the dedication, which eventually led to the formation of the American Astronomical Society.
|Karl Jansky born. He was the world’s first radio astronomer.
|The Russian Venera 9 mission to Venus sent back the first ever mages from the surface of another planet.
|Henry Norris Russell born. He was an American astronomer who, along with Ejnar Hertzsprung, created the Hertzsprung-Russell Diagram and made many other contributions to astronomy.
|Edmond Halley born. A great astronomer and mathematician, Halley discovered much more than the periodicity of the comet now named after him. He found proper motion among the stars, figured out how a transit of Venus could give us the size of the solar system, invented actuarial statistics for use in insurance, and supported the publication of (and applied) Newton’s laws of motion to the heavens.
|The Galileo spacecraft had the first close encounter with an asteroid and sent back the first close-up pictures of an asteroid’s surface.
LAST UPDATED: 2023-10-01