- The Eoarchean (IPA: /ˌiːoʊ.ɑːrˈkiːən/ EE-oh-ar-KEE-ən; also spelled Eoarchaean) is the first era of the Archean Eon of the geologic record. It spans 431 million years, from the end of the Hadean Eon 4031 Mya to the start of the Paleoarchean Era 3600 Mya. The beginnings of life on Earth have been dated to this era and evidence of archaea and cyanobacteria date to 3500 Mya, comparatively shortly after the Eoarchean. At that time, the atmosphere was without oxygen and the pressure values ranged from 10 to 100 bar (around 10 to 100 times the atmospheric pressure today).
- How to find and observe Almach (TOTS#6) (eyesonthesky.com)
Gamma Andromedae is a rather interesting double star within our own Milky Way galaxy. First, the primary is a very yellow star, and the secondary an intense blue. At over 350 light years distance, the light from these stars reaching us today left not long after Christian Huygens proposed that Saturn had rings… in the 1600’s! But the star gets even stranger. The dimmer blue secondary is itself a double star, averaging a Sun/Neptune distance. Stranger still, the primary of THAT system is ALSO double! So Gamma Andromedae is really a quadruple star system.