Scientists Present the Best Timeline Ever for Milky Way

The Milky Way is far larger than most of its neighbors and was formed long ago when smaller galaxies merged. As we know, our galaxy has a thick disk that emerged following the beginning of everything — a process that is known as the Big Bang.

According to the newly created timeline, the galaxy’s original disk arose 2 billion years before the formation of its stellar halo. “We are now able to create a very clear timeline of events in the earliest time of our Milky Way,” Maosheng Xiang, an astronomer, explained.

Maosheng Xiang and Hans-Walter Rix from Max Planck Institute for Astronomy in Heidelberg, Germany, examined almost a quarter of subgiants. Stars belonging to this group literally overgrow as they consume hydrogen during the evolution process happening at their centers.

Cosmis activities in the Milky Way

Astronomers studying stars receive critical information regarding those objects’ lifetime by analyzing their temperatures and brightness of them. This allows scientists to understand how contrast ratings below are in galactic history, which have produced stars with different chemical compositions and different orbits around the Milky Way’s center.

Xiang and Rix found out how the Milky Way’s disk started to combine and reshape almost 13 billion years ago, which is only 800 million years after the universe’s nascent. The Milky Way’s thick disk is estimated to be 6000 light-years from the Sun’s vicinity and has repeatedly formed stars over a long period, nearly 8 billion years ago, according to Science News.

In this period, the team found that the iron content of the thick disk increased 30-fold as exploding stars enhanced the star-forming gas. Moreover, Xiang and Rix discovered a close relationship between the age of a thick disk and its iron content, meaning that the gas in the thick disk was well mixed. The newborn stars began to absorb increasing amounts of iron, regardless of their location.

With all these happening, many researchers reported in 2018 about how a different galaxy hit ours and gave Milky Way most of the stars in its halo. As the thick disk in question used up gas, it deactivated the process of forming stars 8 billion years ago. And today as a young galaxy, the Milky Way’s thin disk is about 2,000 light-years.