On this day in 1987 - February 23rd - the light from supernova SN 1987A reached Earth.
The supernova occurred in the Tarantula Nebula in our neighboring galaxy the Large Magellanic Cloud. It was the closest supernova seen in nearly four hundred years, visible to the unaided eye in the southern hemisphere. It has greatly increased our understanding of this spectacular phenomenon.
On this day in 1945 - February 23rd - Ukranian astronomer Svetlana Gerasimenko was born.
Gerasimenko was the co-discoverer of comet 67P/Churyumov–Gerasimenko, the comet which was studied by the Rosetta mission. Both the Rosetta spacecraft and the lander Philae are on the comet as it continues its orbit.
On this day in 1968 - February 24th - the discovery of the first pulsar was announced.
A pulsar is a fast-rotating neutron star that emits a beam of electromagnetic radiation. We can only detect it when it's pointing towards us, rather like a lighthouse, so it seems to pulse. A neutron star is the remnant of a massive star following the collapse of its core in a supernova explosion.