The sun, like all stars, was born in a giant cold cloud of molecular gas and dust. It may have had dozens or even hundreds of stellar siblings – a star cluster – but these early companions are now scattered throughout our Milky Way galaxy
Compared to some other galaxies in our Universe, the Milky Way is a rather subtle character. In fact, there are galaxies that are a thousands times as luminous as the Milky Way, owing to the presence of warm gas in the galaxy’s Central Molecular Zone (CMZ). This gas is heated by massive bursts of star formation that surround the Supermassive Black Hole (SMBH) at the nucleus of the galaxy.
In the 1970s, astronomers discovered that a particularly large black hole (Sagittarius A*) existed at the center of our galaxy. In time, they came to understand that similar Supermassive Black Holes (SMBHs) existed in the center of most massive galaxies. The presence of these black holes was also what differentiated galaxies that had particularly luminous cores – aka. Active Galactic Nuclei (AGN) – from those that didn’t.
The Phoenix cluster is an enormous accumulation of about 1,000 galaxies, located 5.7 billion light years from Earth. At its center lies a massive galaxy, which appears to be spitting out stars at a rate of about 1,000 per year. Most other galaxies in the universe are far less productive, squeaking out just a few stars each year, and scientists have wondered what has fueled the Phoenix cluster’s extreme stellar output.