January 05 – Discovery of Eris (2005)

Dwarf planet Eris is the largest known member of a collection of objects known as the scattered disc, a subset of the larger group, the trans-Neptunian objects (TNOs).  It was discovered by a team from Palomar Observatory on January 5th 2005, and was given the “minor planet designation” of 136199.  Eris has a larger mass than Pluto by about 27% (and was partly responsible for the reclassification of Pluto by the IAU as a dwarf planet), making it the ninth most massive object orbiting the Sun.

Eris - Troublemaker
Eris – Troublemaker

Eris, and its moon Dysnonia, are a very long way away.  They orbit in a wild ellipse ranging from 38 to 97 AU from the Sun (about three times farther away than Pluto).

Eris has an appropriate name.  In Greek mythology she was the goddess of chaos and discord.  Inhabitants of Pluto, if they exist, would surely agree.


1969  –  Launch of the USSR’s Venus atmospheric probe Venera 5 from Baikonur Cosmodrome in Kazakhstan.  It reached its target on May 16th, and sent back data for almost an hour while descending by parachute through the Venusian atmosphere.