Hello everyone and welcome back to my blog! I thought I was done with reading, but this week I read the paper that first proposed quasistars: “Formation of Supermassive Black Holes by Direct Collapse in Pregalactic Halos” by Begelman et al. I also did some work on my model along with that, so I’ll summarize what I read and what I did in a way that you will hopefully understand.

Quasistar formation

In order for a gas cloud to host a quasistar, the matter in the center needs to be spinning slow enough for it to come together into one big object. In order for this to happen, the central gas first coalesces into a bar shape. This shape allows it to transfer its momentum to the outer regions of the gas cloud. After it has transferred some of its momentum, the central region of the bar turns into a separate bar and repeats the process. Once it has transferred enough momentum, it is able to condense into a gigantic star. As the core of the star gets hotter and hotter, it pushes against gravity more. However, once it approaches a temperature of 1 billion Kelvin, it starts making tiny particles called neutrinos, which carry away some of the energy. This makes the core too cold to continue resisting the star’s own gravity, causing it to collapse.

Quasistar growth

When a quasistar’s central black hole first gets created, it has a mass of under 20 solar masses. After it forms, the quasistar keeps a relatively constant radius of a few times the distance between the earth and the sun. It is able to do this because quasistars pull in mass from their environment while being consumed from the inside.

A small hiccup

As part of the work on my model, I tried to calculate the temperature that the Milky Way would be at during the time frame of quasistars existing. The Milky Way has a mass that indicates it could’ve hosted a quasistar, so I expected to get a value that went along with what I saw on the papers I read, that being around 10,000 Kelvin. Instead, I got a temperature that is so small that it literally couldn’t ever occur. I kept trying to find what I did wrong, but I couldn’t understand. I asked my senior project advisor for help, and he managed to calculate a value of 9,800 K. As it turned out, I mistakenly swapped out one constant (h) with another (h). I honestly blame whoever came up with the variables though, because there is no reason for two constants to use the same letter when one is 10^33 times bigger than the other.

Anyway, this week was my actual last reading, and I’ll be fully focused on my model from now on. I hope you all liked this post, and I hope to see you in the next one!