The biggest stars of our universe which could ever have formed are thought to have existed billions of years ago, when the universe just came into existence after the Big Bang. Those stars were gigantic. Some of them were even more than 1000 times as massive as our Sun. Those massive hypothetical stars are also called quasi-stars or black hole stars because they contain a black hole at its core.
However, one of the biggest stars which is known from our time is the star BAT99‑98 in the Large Magellanic Cloud, which is only 226 times as massive as our Sun in comparison to those enormous stars. This star is located near the R136 cluster.
What are Quasi-Stars?
Quasi-stars are no longer found in our universe. Because of their gigantic size, they would have had a short maximum lifespan of about 7 million years. Some scientists also speculate that the supermassive black holes, which are found at the center of modern galaxies, might have been formed from those black hole in the core of the quasi-stars.
These black hole stars were not powered by nuclear fusion occurring in their cores like modern stars. Their brightness and energy would come from the material falling into the massive black hole in their core.
READ ALSO : What is inside of a Black Hole?
How are Quasi-Stars formed?
When the core of a large protostar collapsed into a black hole and the outer layers of the protostar were massive enough to absorb all the resulting burst of energy without being blown away and those outer layers did not fall into the black hole, it formed those huge quasi-stars.
Thus, there was no supernova explosion during the formation of the black hole in the core. Once the black hole formed at the core of the quasi-star, it produced enormous amount of radiant energy from the stellar material falling into the black hole.
READ ALSO : What is a Supernova Explosion?
Do Quasi-Stars still exist?
In this generation of stars, such huge stars can no longer be found in our universe because there is too much contamination from elements heavier than hydrogen and helium. Just after the Big Bang, when our universe came into existence and the first stars were not formed yet, there were no such heavy elements in our universe.
READ ALSO : The Big Bang – Beginning of time
How hot is a Quasi-Star?
These enormous stars had surface temperatures of approximately 10,000K or 9,700 °C and they were almost 7000 times as big as our Sun. During their short lifespan, they are thought to have cooled to temperatures of about 4000K. Then, those stars gradually start to dissipate and eventually die which would leave behind just the black hole.
READ ALSO : How hot is the Surface of the Sun?