Can the earliest stars tell us where we come from?

We know that the birth of the universe was the Big Bang. A huge explosion resulted in the formation of stars and galaxies. But we still don't know how they actually formed. A new research project will now try to add another piece to the puzzle.

»In recent decades, we have tried to understand how stars and galaxies form. We have done it in the same way as you look at butterflies. You look at them in different shapes, colours and sizes. But even if you find more and more butterflies or more and more galaxies, it doesn't tell us anything about how they form,« says Kasper Elm Heintz, who will lead the research, and adds:

»Now we can actually look at the pupa, i.e. how they are formed. We can dissect the process of the creation of the first stars and galaxies.«

Kasper Elm Heintz is an assistant professor at the Niels Bohr Institute at the University of Copenhagen and has received support for his research in the form of a Sapere Aude grant from Independent Research Fund Denmark. He is responsible for developing the two methods that are the primary in the research work.

Modern telescopes make it possible to find new clues

It is the powerful telescopes, such as the James Webb Space Telescope, that make it possible to look so far back in the history of the universe that we can learn more about how stars are formed.

One of the methods that Kasper Elm Heintz and his project group will work with regards the absorption of light.

Because when you study the light from some of the earliest galaxies, there is some light of a certain wavelength missing. In other words, something must have absorbed the light.

»We can measure it very precisely. You can imagine that it is just like if you form shadow images. You hold up a cone of light, which in this case is the stars in the galaxy, and when you hold up a few fingers, you can very precisely look at the light that is missing, i.e. at the shadows. From that, you can see how much gas there is and what type of gas it is, and thus how quickly it builds up in the galaxies and how quickly the stars are formed,« says Kasper Elm Heintz.

The second method tries to solve a problem, namely that you can only immediately look at the gas that is in the light cone. Just like if you point your flashlight at a cabinet in the dark, you can't immediately see what's behind the cabinet.

Therefore, the project group, which in addition to Kasper Elm Heintz will consist of a PhD student and a postdoc, will retrieve images from the ALMA telescope in Chile.

The earliest stars were formed from hydrogen and helium. Before a star could form, however, the gas it was supposed to consist of had to cool down a little. Meanwhile, neutral oxygen was emitted from the gas cloud, i.e. oxygen atoms that are not electrically charged, to which the researchers can measure the ratio of hydrogen.

Using ALMA's measuring equipment, it is possible to measure how much neutral oxygen was present, and thus the researchers can calculate the amount of hydrogen and helium. 

»So if we use these two methods, we get a one-dimensional, but direct target for the gas. And then we have the two-dimensional, but more calculated measure of the gas. So if we piece it together, we may be able to get a complete understanding of how this gas is structured, how it is distributed, how it drives the stars and so on,« explains Kasper Elm Heintz.

The star factory was busy for the first 100 million years

It is already known that far more star formation took place immediately after the Big Bang than happens now. The universe has found a kind of equilibrium state in which the formation of stars proceeds at a slow pace.

In fact, the number of galaxies that formed during the first 100 million years has surprised scientists. The same applies to the brightness of galaxies.

»The hope is that we can try to answer some of these big questions with a concrete answer to why it looks the way it does. But also just that we get an understanding of what is actually happening and what processes are taking place in this early universe,« says Kasper Elm Heintz about the hopes for the four-year research project.

»When I'm out giving lectures, it's clear that people are very interested in it. And it also gives a completely different curiosity and understanding of how the universe around us works. It is driven by the curiosity to try to understand this big question: Where do we come from? Now we are just starting to be able to actually look all the way back to the moment of formation and try to understand it,« he concludes.