Hakim Atek

A researcher at the Paris Institute of Astrophysics, Hakim Atek is interested in the formation and evolution of the very first galaxies. Using the latest generations of space telescopes and gravitational lenses, he is seeking to understand how low-mass galaxies helped reionize the early Universe. His work was recently published in the prestigious journal Nature. 

A scientist who sees far. Very far. From his laboratory at l’Institut d’astrophysique de Paris (IAP), part of Sorbonne University, Hakim Atek observes the galaxies that existed a few hundred million years after the Big Bang. Until now, little has been known about this period, but it provides an insight into how the universe was structured in its early days.

Closer to the Big Bang

Using the Hubble Space Telescope as a starting point, followed by the James Webb, launched in December 2021, Hakim Atek is seeking to understand the role of dwarf galaxies, composed of just a few million stars, in the reionization of the universe. This process, which took place during the first billion years after the Big Bang, allowed the neutral hydrogen present in the universe to dissipate and light to pass freely through it. “It's one of the most important transitions in the history of the universe,” explains the scientist on the terrace of the IAP, a stone's throw from Paris Observatory.

With a team of researchers from several countries, Hakim Atek has succeeded in demonstrating the important role played by these low-mass galaxies. “We've confirmed that small galaxies outnumber massive ones by a hundred to one. The most astonishing result is their ionizing power. It's much greater than we thought. They are four times more effective than normal galaxies. It also tells us how galaxies were distributed in the very early universe”, explains the astronomer.

“Understanding our place in the universe"

This discovery would not have been possible without the exceptional sensitivity of the James Webb Space Telescope (JWST). Launched jointly by NASA and Esa, the European space agency, this bus-sized space telescope makes observations in the infrared, enabling it to go back in time to a few hundred million years after the Big Bang. “We have lots of theories, and if we don't confront them with observation, it's hard to move forward. To explore the distant universe, the young universe, we need more powerful telescopes, and we need to launch them into space”, says Hakim Atek.

A native of Kabylie, Algeria, in his forties, Atek has always had a passion for science and astrophysics. “What fascinates me is understanding our place in the universe. We've always explored what's going on, from hunter-gatherers to navigators. I've always thought that it's the role of human beings to understand the universe, and not just our immediate environment”, explains the researcher, a member of the French National Corps of Astronomers and Physicists (Cnap).

“A lab without walls"

After defending his thesis on the Lyman-alpha hydrogen recombination line in September 2009, Hakim Atek took off on a post-doc at Caltech, the California Institute of Technology, until 2012. He then joins Switzerland's École Polytechnique Fédérale de Lausanne, recognized as one of the world's top scientific schools, for another post-doc until 2015. He completes his training for a further year as a research associate at Yale University, USA, before being recruited to IAP in 2017. “International experience is highly recommended in this field, because it opens up a lot of avenues and collaborations. It also allows you to see different ways of working. At the IAP, you don't just work with your colleagues in the office next door. It's a lab without walls,” adds Hakim Atek.

At the same time, he is leading a 100-strong working group on the primordial universe, using the European space telescope Euclid, which was launched a year ago and produced its first results a few weeks ago, published by ESA. After the summer, he will lead another program in which the JWST will observe a region of the sky for 150 hours, using another gravitational magnifying glass to get even closer to the Big Bang and detect the very first galaxies in the universe. “What is their stellar content, how old are these stars and, above all, what are the conditions under which these galaxies were formed? The observations are due to arrive in September”, sums up Hakim Hatek.