International meeting discusses period when universe was young

Stars, galaxies and black holes that began to form approximately 30 million years after the Big Bang were discussed during a course supported by FAPESP and held in Brazil to prepare researchers for the next stage in world-class astronomy.

By José Tadeu Arantes  |  Agência FAPESP – Participation in large-scale international observation projects, several of them supported by FAPESP, has contributed to the growth of research on astronomy in Brazil in terms of quality as well as quantity. Among these projects are the Southern Astrophysical Research Telescope (SOAR), located on Cerro Pachón in the Chilean Andes, and the Gemini Observatory, which has “twin” telescopes, one in the Chilean Andes and the other in Hawaii.

Astronomers based in Brazil are now major world players but face the daunting challenge of creating the expertise necessary to participate in the next stage of discovery, which will be made possible by the massive telescopes scheduled to go live in the near future.

One of these is the Giant Magellan Telescope (GMT), now under construction at the Las Campanas Observatory in Chile and due to see first light in 2024, with an effective aperture of 24.5 m. FAPESP will invest USD 40 million in the GMT, or approximately 4% of the total estimated cost. This investment will guarantee 4% of the telescope’s operating time for study by researchers from the state of São Paulo.

Telescopes of this size will enable scientists to observe ever more distant – and more ancient – objects, providing precious data on the infancy of the universe and ratifying or rectifying current theoretical models. The challenge for Brazilian astronomers is to go beyond knowledge based mainly on the observation of the local universe and to equip themselves to address questions raised by data from the extremities of the cosmos.

This was the task of the São Paulo School of Advanced Science on First Light: Stars, Galaxies and Black Holes in the Epoch of Reionization, which took place July 28-August 7, 2019, at the University of São Paulo’s Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG-USP) in São Paulo, Brazil. The School was supported by FAPESP via its São Paulo School of Advanced Science (SPSAS) program. 

“The School focused on the Epoch of Reionization. We invited some of the world’s leading experts to lecture and selected 100 outstanding PhD students to attend, 50 from Brazil and the rest from other countries. Selecting them was tough as we had more than 300 applicants, all with first-rate academic credentials,” Laerte Sodré Jr., the school’s co-chair, told Agência FAPESP. A full professor and the ex-director of IAG-USP, Sodré also chairs the São Paulo Astronomy Network (SPAnet).

The term reionization refers to a process that occurred approximately 1 billion years after the Big Bang. The young universe, a hot soup of fundamental particles, was ionized because its very high temperature prevented electrically charged particles from forming neutral structures. After approximately 500,000 years, it had cooled enough for protons and electrons to combine to form neutral hydrogen. This gave rise to the first atoms. The first- and second-generation stars reionized nearby regions. Over time, as new stars and galaxies were formed, the ionized regions merged, leading to the large-scale reionization of the universe.

“The São Paulo School of Advanced Science on First Light focused on this period, thought to have been rich in events but still poorly understood. One of the key challenges is observing these distant galaxies and stars that formed in the epoch of reionization. No announced observation has so far been recognized by a majority of the scientific community, above all because the signals received are extremely weak,” Sodré said.

“The universe was made up mostly of hydrogen atoms at the onset of reionization, so observations are typically made in the neutral hydrogen emission band, but huge numbers of objects emit at the same frequency, from cell phones to accelerated electrons in the Milky Way. The signal we need to measure is almost a thousandth of the signal we receive,” he continued.

The strategies researchers use to improve access to data from the young universe include taking advantage of gravitational lensing, a natural phenomenon that consists of distortions in the geometry of spacetime due to the gravitational pull of massive objects positioned between the light source and the observer. It was predicted by Einstein’s general theory of relativity and later confirmed by astronomical observation.

A lecturer at the São Paulo School of Advanced Science on First Light, astronomer Adi Zitrin is a professor at Ben Gurion University of the Negev, Israel, and specializes in this procedure. “Gravitational lensing lets us explore the universe further and better. When we count the galaxies in the sky, we find that there are many more weak galaxies than bright galaxies. We could say these weak galaxies were the first ones responsible for reionization, simply because they’re far more numerous. The trouble is that these galaxies are hard to observe. Gravitational lensing facilitates observation, giving us access to objects that would be inaccessible with present equipment,” Zitrin told Agência FAPESP.

The new telescopes under construction will enable scientists to investigate this period more accurately, and there is enormous expectancy about the telescopes. The Hubble Space Telescope, launched into low Earth orbit in 1990, has provided humanity with a staggering amount of information on the solar system and so-called deep space. The GMT’s resolving power will be ten times greater than the Hubble’s.

“These telescopes are specifically designed to help investigate the young universe. Participation in projects like the GMT will bring these powerful resources within reach for our community, but it’s vital for us to prepare a generation of astronomers to deal with the period, including aspects such as the galaxy formation process, for example. That’s precisely the point of an international event like this school,” said Roderik Overzier, a researcher at Brazil’s National Observatory in Rio de Janeiro and co-chair of the São Paulo School of Advanced Science on First Light.