Gamma-rays help us understand how the universe was formed

A physicist from the University of São Paulo talks of the CTA, which will be the world’s largest gamma-ray observatory, and of the studies she conducts with high-energy phenomena in astrophysical systems.

By Heitor Shimizu, in New York  |  Agência FAPESP – Only a small fraction of the universe consists of known matter, made up of atoms and molecules. More than 95% of it is dark energy and dark matter about which little is known. But thanks to a group of Brazilian scientists and the new generation of astronomical tools, this knowledge is about to increase.     

“Most of the visible matter in the universe is in a plasma state, or more specifically, is composed of partially ionized gas permeated by magnetic fields,” said Elisabete de Gouveia Dal Pino, a professor at the Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG) of the University of São Paulo (USP).

Dal Pino talked about “High-energy plasma astrophysics phenomena and the next generation of gamma-ray observatories” at FAPESP Week New York, organized jointly by the City University of New York (CUNY) and the Wilson Center November 26-28, 2018 at the Graduate Center da CUNY. 

“In recent years, important advances in this field have been achieved both by means of multidimensional magnetohydrodynamic studies and through observations with very-high-energy gamma-ray detectors located in space and on the ground,” she said.  

Magnetohydrodynamic methods constitute a powerful tool for the study of conductive fluids, as in the case of plasmas. 

The researcher talked about the recent progress achieved in the investigation of plasmas and high-energy phenomena in astrophysical systems by means of high-performance computing. The studies focus on physical processes like particle acceleration and non-thermal radiation around black hole sources.   

Dal Pino is leading a FAPESP-funded project that has enabled the advance of knowledge about astrophysical plasmas. One of the highlights of the research has been the study of the acceleration of cosmic rays in regions of magnetic reconnection (read more about it at: agencia.fapesp.br/16821/). 

In the astronomy department at IAG-USP, Dal Pino’s group is studying gas dynamics and high-energy phenomena in a wide variety of astrophysical systems, from the sun to galaxy clusters, employing mostly magnetohydrodynamic methods.  

“We utilize sophisticated numerical algorithms in our studies in order to conduct multidimensional numerical simulations of astrophysical sources and diffuse means involving high-performance computing, of such things as accretion disks and black hole supersonic jets, including microquasars, active galactic nuclei and gamma-ray bursts, as well as young stellar objects,” she said.   

“We are also investigating the acceleration and propagation of cosmic rays, stellar and galactic winds, the role of turbulence and magnetic fields on star formation, the origin of cosmic magnetic fields and the astrophysics of gamma-rays,” said Dal Pino, who is a member of the High-Energy Astrophysics Commission of the International Union of Pure and Applied Physics. 

Gamma-rays are the highest frequency electromagnetic radiation produced by relativistic particles (cosmic rays) interacting with magnetic fields, low-frequency photons or particles with lower energy than the gas. This type of high-energy radiation is generally produced through violent astrophysical processes.

To enhance our knowledge of gamma radiation, construction is underway on the Cherenkov Telescope Array (CTA), which will be the largest gamma-ray observatory in the world and will feature a set of 120 Cherenkov type telescopes – capable of detecting Cherenkov radiation produced when a gamma-ray from space hits Earth’s atmosphere, producing showers of pairs of electrons and positrons. The CTA will offer 10-fold increased sensitivity at TeV energies (10¹⁵ eV) or a few hundred TeV over the best gamma-ray detectors currently available.  

“The CTA will enable us to understand the non-thermal and high energy universe in a new way, through important contributions to cosmology, particularly regarding the origin of dark matter, astrophysics, particle astrophysics and plasma phenomena,” said Dal Pino. 

FAPESP is supporting Brazilian researchers’ participation in the project through the thematic project entitled, “Investigation of high-energy and plasma astrophysics phenomena: theory, numerical simulations, observations and instrument development for the Cherenkov Telescope Array (CTA)”, led by Dal Pino. 

“We are currently directly involved in a partnership with institutions from Italy and South Africa in building the ASTRI mini-array, which is a set of nine Cherenkov telescopes with primary mirror diameters of 4.3 meters that will be the precursor to the CTA,” said Dal Pino. 

Dal Pino’s group at the IAG-USP is responsible for building three of the nine ASTRI telescopes. 

Read more about the CTA at: agencia.fapesp.br/25605. 

Watch the Ciência Aberta program on the origin of the universe, featuring Elisabete de Gouveia Dal Pino, João Steiner and Carola Dobrigkeit Chinellato, at: http://www.fapesp.br/ciencia-aberta/origem-do-universo-em-debate-no-programa-ciencia-aberta/14. 

For more information about FAPESP Week New York, visit: www.fapesp.br/week2018/newyork.