Slovenian researcher helping to design James Webb Space Telescope

One of the main purposes of the James Webb Space Telescope is to observe and study the first galaxies in the universe, which are more than 13 billion years old, almost as old as the universe itself.

One of the people studying the oldest galaxies is Slovenian astrophysicist and galaxy and dark matter researcher Maruša Bradač, who works at the University of California, Davis.

Galaxies are systems of stars, stellar remnants, interstellar gas, dust and dark matter. The best known among them is the Milky Way, the galaxy which includes our Solar System.

Only a hundred years ago it was believed that the Milky Way is the only galaxy in the universe, today we know that this is far from the truth, as scientists estimate that there are at least 100 billion galaxies in the universe.

Using large telescopes, such as the Hubble and Spitzer, and the Keck telescopes in Hawaii, astronomers may travel back in time and observe the universe at the moment when its age was around 1% of today's age.

Such time travel gives provides then with insight into the earliest years of the oldest galaxies.

While observing galaxies which are billions of light years away from the Earth, scientists see the light emitted by an object billions of years ago, as light travels with the speed of 300,000 kilometres per second.

Studying early galaxies is a great challenge

Studying early galaxies is a great challenge for researchers, since the light they emit is very weak. Light emitted by objects so distant from the Earth grows weaker, and the first galaxies also have fewer stars, which additionally contributes to their weakness.

This is why the largest and most powerful telescopes are needed to observe the most distant galaxies. One of the most important instruments since the 1990 is the Hubble Space Telescope, which enabled the observation of galaxies from the "universe's adolescence".

Its successor, the James Webb Space Telescope, which is to be launched in 2021, is expected to provide scientists with a more detailed insight in the more distant objects, which emit much weaker light.

James Webb Space Telescope

Bradač has participated in designing the James Webb Space Telescope built by NASA, which is the size of a tennis court. This is an exceptional achievement for the Slovenian astrophysicist, whose research team has developed an observation project for one of the instruments for the new telescope in cooperation with researchers from Canada.

This is why they will be given the exceptional opportunity to observe the universe with it and be among the first scientists in the world to obtain data from the telescope. The team is currently undertaking intensive preparations for this.

"It's a telescope which is directly connected with my research and I have high hopes. We know approximately what we'll see. But the most interesting findings will be those we can't even imagine the telescope will give us," says Bradač.

The launch of the James Webb Space Telescope is being delayed, with the latest available information saying that it is to be sent into space in March 2021. "We're all on pins and needles. I've invested a big part of my career in this telescope and every delay is problematic. The plans by doctoral students, who are being promised to get data, are falling apart."

One of the reasons the launch is most probably being delayed is because there will be no opportunity to correct mistakes. Unlike with Hubble, no corrections will be possible once it is launched. James Webb will travel far further into outer space, and will not be reachable with a space mission.

The James Webb Space Telescope is designed with the purpose of discovering galaxies on the edge of the universe, which is why it is much more powerful than its predecessor - the Hubble Space Telescope. Researchers expect that it will discover many more galaxies than Hubble and provide a much clearer picture about what these galaxies are like, says Bradač.

Who we are and where we came from

According to Bradač, studying galaxies and dark matter is about looking for answers to the fundamental question of how life came to be. "It's about scientific curiosity, which is always present. It's therefore important that this research is done, even though some do not see it as useful at all," she says.

"Science gives us a lot, it needs to be pushed forward, as this is the only way to get things to which we are very attached today. It was astronomers who discovered that it's possible to record a picture by means of memory cards. This is how first light detectors, and later CCD sensors, a key element of today's cameras, were invented. What we have in our phones today, what we take pictures with, is a result of astronomical development of cameras," explains the astrophysicist.

Discovery of the darkest and oldest galaxy

An international research team headed by Bradač discovered the darkest known galaxy in 2016, and one of the oldest galaxies, the MACS1423-z7p64, in 2017. The latter is 13.1 billion light years away from the Earth, and was formed 13.5 billion years ago. It is the first ordinary galaxy from that period discovered, and an alleged "culprit" for the universe "clearing up".

In the early aftermath of the Big Bang, the universe was shrouded in a mist, which scientists call the "dark ages". The mist was dispersing over the next several hundred million years. This period, when the universe was making the transition from the "misty" state with neutral hydrogen into the transparent state with ionised hydrogen, is described by researchers as the period of reionization, which is believed to have lasted between 400 million and 1.3 billion years after the Big Bang.

According to Bradač, the discovery of the oldest galaxy enabled further research into the formation of the first galaxies and stars constituting galaxies, and provided direct insight into the universe as it was at the very beginning. The research showed that stars started to form much earlier than it had been initially thought, which brings changes to the theory about the formation of the first stars and makes researchers change the existing models, Bradač explains.

Research of dark matter

A major part of the astrophysicist's work is research into dark matter, the unknown substance which accounts for 27% of the known universe. Dark matter is very important for both the past and future of the universe, as it slows down the expansion of the universe by means of gravity. Dark energy, which accounts for 70% of the universe, is what makes the universe expand at an accelerated rate.

Bradač researchers dark matter by studying the collisions of clusters of galaxies which happened in the past, and observes how dark matter behaves after a collision. Such collisions release a large quantity of energy, some of the largest in the universe, which is why Bradač believes that they have a dark matter accelerator of their own.

Since dark matter does not interact with ordinary matter, studying it is a great challenge. Although researchers distinguish between a large number of particles today, none of them match the description of dark matter. "We're looking for a needle in a huge haystack, and if we search only a small part of the haystack, we'll probably not find the needle. Now we have to search the entire haystack, which will take quite a while."

Cooperation with Slovenian researchers

Since October 2019, Bradač has been on a sabbatical at the University of Ljubljana and is doing her research from Slovenia. She also cooperates a lot with Slovenian researchers on other projects, and would like to see a Slovenian student come to California to do research.

She is trying to inspire students at the University of California, Davis, to learn physics through her course Physics of California, where she teaches the physics of skiing, snowboarding and diving. She takes students into the world of physics not by means of equation, but through everyday activities they are familiar with.

Bradač has found that students are very enthusiastic about astronomy, "because astronomy is attractive, interesting, and a lot of research is done in this field, and we have a good basis for this in Slovenia". She is aware that young people are justifiably worried about their job prospects after such studies if they do not decide to continue their careers in research, but abroad, and in particular in the US, this is not a problem.

According to her, companies such as Google or large insurers "are happy to employ students from this field, because they know how to make models and project their behaviour in the future, they know how to work with data, process it and write programs which process this data. Things are beginning to change in Slovenia, so I would like to tell students that it really pays to study physics, as it offers many opportunities."