Short answers, pulled from the story.
The Nebra sky disc is a bronze artifact inlaid with gold symbols representing the sun, moon, and a cluster of seven stars that was discovered in Germany in 1999. This object dates back to approximately 1600 BCE and functioned as a sophisticated calendar for Neolithic populations to track the heliacal rising of Sirius.
Aristarchus of Samos proposed a heliocentric model where the Earth and planets rotated around the Sun by the 3rd century BC. Nicolaus Copernicus revived this heliocentric model during the Renaissance, maintaining circular orbits before Galileo Galilei confirmed the theory with telescopic observations in the 1600s.
Edwin Hubble used the Hooker Telescope to identify Cepheid variables in the Andromeda Nebula and Triangulum in 1922 and 1923. This discovery proved conclusively that these nebulae were entire galaxies outside our own, expanding the known universe from a single galaxy to a multitude of island universes.
Cosmic microwave background radiation was discovered in 1965 and provides the first experimental evidence to support the Big Bang theory proposed by Georges Lemaître in 1927. This radiation is a remnant of the early universe and confirms that the universe began as an extremely dense and hot point 13.8 billion years ago.
The LIGO project detected gravitational waves from a binary black hole on the 14th of September 2015. This observation marked a new era in astronomy by allowing scientists to observe the universe through a medium other than electromagnetic radiation.
Karl Jansky discovered a radio source at the center of the Milky Way, pioneering the field of radio astronomy. This discovery demonstrated that amateurs could make groundbreaking contributions to the field and allowed astronomers to observe interstellar gas, pulsars, and fast radio bursts.