The Milky Way Galaxy
By Maina Kiarie
The formation of the Milky Way Galaxy, commonly referred to as just the Milky Way, or sometimes simply as the Galaxy, took place 8.8 billion (plus or minus 1.7 billion) years ago
The Milky Way Galaxy is the home galaxy of the Solar System, and of Earth. The Milky Way contains 200-400 billion stars and is estimated to have at least 50 billion planets, 500 million of which could be located in the habitable zone of their parent star. It is is one of around 200 billion galaxies in the observable universe.
The Milky Way is comprised of a “thin” stellar disk and a much thicker halo of gas extending beyond the stellar disk.
Thin “thin” stellar disk formed between 8.8 ± 1.7 billion years ago. In 2007, a star in the Galactic halo (HE 1523-0901) was estimated to be about 13.2 billion years old, nearly as old as the Universe. There was a hiatus of almost 5 billion years between the formation of the halo and the thin disk.