140 AD
Claudius Ptolemy of Alexandria wrote the Almagest, an astronomical treatise recording all the knowledge of the ancient world. He also produced the most accurate star catalogue of his time.
1054 AD
Chínese astronomers recorded a supernova explosion in Taurus. The Crab Nebula is the remnant of this event.
1543
Copernicus laid the groundwork of modern astronomy by showing that the Earth and all the planets revolved around the Sun.
1608
The Dutchman, Hans Lippershey, used the magnifying power of glass lenses to build the first telescope. The following year, Galileo used his own telescope to observe sunspots, the moons of Jupiter and the stars oftheMilky Way.
1671
The first telescopes were crude refractors. In 1671, Newton invented the reflecting telescope. Though only 16 cm long, it was as powerful as a 200 cm refractor.
1937
Grote Reber built the first true radio telescope. He set up a 9 m reflecting dish in his garden to study the radio noises that carne from the sky.
1960
Radio astronomers discover quasars (quasi-stellar radio sources). These puzzling objects lie at tremendous distances from us—as much as 15,000 million light years away. They are a fraction the size of galaxies yet hundreds of times brighter.
1967
Unexpected signals from space were discovered by astronomers at Cambridge, England. These unknown pulses turned out to be coming from rapidly spinning neutron stars. They were called pulsars. One has been found in the middle of the Crab Nébula, right at the heart of the supernova explosion of 1054.
1987
In a small nearby galaxy, the Large Magellanic Cloud, a blue supergiant star blew up. This supernova, as an exploding star is called, was 160,000 light years away, and was the nearest ío the Earth since the telescope was invented.
1990
The Hubble Space Telescope, with a 2.4-m mirror, was launched into orbit.
