On this date in 1877, American astronomer Asaph Hall discovered the first small moon known to be orbiting Mars. Scientists now think this moon – called Phobos – is the latest incarnation of a cyclic ring-moon formation process that goes back billions of years.
In 1543, Copernicus tried to show the world that medieval beliefs of an enclosed, Earth-centered universe were wrong. Instead, he said, Earth revolves around the sun. His work set off what’s known today as the Copernican Revolution.
On this date in 1930, Clyde Tombaugh was searching for a 9th planet when he discovered Pluto. In doing so, he unknowingly opened the door to the vast “3rd zone” of our solar system, known today as the Kuiper Belt.
After 24 successful missions, shuttle launches seemed routine. That’s why those watching the launch of the space shuttle Challenger on January 28, 1986, started out excited, but soon were in a state of disbelief. Then NASA confirmed the worst.
Voyager 2 swept closest to Uranus on this day 34 years ago. During its visit, the spacecraft sent data that revealed 2 new planetary rings, 10 new moons, radiation belts, and a very unusual magnetic field.
Born on today’s date in the year 1656, English astronomer and mathematician Edmond Halley was the first to predict the return of a comet. Today, Halley’s Comet – the most famous of all comets – bears his name.
Our global human population was estimated to reach 6 billion on today’s date in 1999. Eleven years later, in 2011, Earth had gained another billion people. Today – October 12, 2019 – it stands at about 7.7 billion, according to United Nations estimates.
On October 6, 1995, astronomers Michel Mayor and Didier Queloz announced the momentous discovery of the 1st planet in orbit around a distant sunlike star. 51 Pegasi b has about half the mass of Jupiter. It orbits a star not unlike our sun.