Brazil builds high-resolution spectrograph

Equipment will be installed at the SOAR telescope in Chile, says Bruno Vaz Castilho, director of the Brazilian National Laboratory for Astrophysics.

By Karina Toledo, in Itajubá (MG)

Agência FAPESP – Researchers at the Brazilian National Laboratory for Astrophysics (LNA) in Itajubá (MG) are nearing the completion of construction on the first Brazilian high-resolution spectrograph, known as STELES (SOAR Telescope Èchelle Spectrograph).

The expectation is that the equipment – long-awaited by the astronomy community – may be installed in early 2015 at the Southern Observatory for Astrophysical Research (SOAR) in Chile, operated by an international consortium of Brazilian, North American and Chilean partners.

“High-resolution spectroscopy is a technique that allows capturing the visible light of a celestial body – a star, nebula or galaxy – and separating it into its various wavelengths. That way, it’s possible to perceive the lines of light absorption through the various chemical elements that constitute the object under study,” explained Bruno Vaz Castilho, director of the LNA and coordinator of the project team that designed and assembled the instrument.

By studying light absorption lines, astronomers are able to calculate the quantity of calcium, iron, titanium and other elements found in the atmosphere surrounding a celestial body. It is also possible to determine its mass, radius, gravity, temperature, rotation speed and the existence of other planets or stars around it.

“It’s a very valuable technique for astronomy, and increasingly effective equipment has been developed all over the world. The STELES boasts state-of-the-art technology that will have extremely high resolution, giving it the ability to capture most of the photons that reach it,” Castilho noted.

According to the LNA director, the equipment cost R$2.5 million – R$1.2 million of which was financed by FAPESP through the project, “STELES: a high-resolution spectrograph for SOAR”, coordinated by Prof. Augusto Damineli of the Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG) at the University of São Paulo (USP). The remaining portion was financed by the Ministry of Science, Technology and Innovation (MCTI).

“It would cost at least R$4 million to import similar equipment. Besides being more expensive, high-resolution spectrographs with similar technology are usually larger and heavier. Our challenge was to use the available resources to develop a compact instrument that could be attached to the SOAR telescope, whose diameter is 4.2 meters,” Castilho said.

Made up of more than 5,000 parts, each designed by LNA researchers, the STELES was first conceived in 2003, but construction only began in 2008, Castilho explained.

“Up to now, Brazilian astronomers have depended on partnerships with groups based abroad and had adapted their studies to the instruments available to them. The STELES will allow them to do more advanced science in various areas in which Brazil has important research, especially because the country has the right to 30% of the observation time on the SOAR telescope,” Castilho said.

Damineli is one of several researchers who are expected to benefit from the new spectrograph. For more than 20 years, the IAG professor has had FAPESP support in studying the mysterious phenomena that involve a giant star known as Eta Carinae, situated nearly 8,000 light-years from Earth in the constellation Carina (read more about it at: http://agencia.fapesp.br/19625).

For the past 5.5 years, Eta Carinae has been experiencing a type of blackout. By studying the phenomenon, the team of astronomers led by Damineli have discovered the existence of a binary system in which, from time to time, the smaller star collides with the larger one and creates a hole in its surface.

The most recent occurrence of this was in July 2014, and it mobilized more than 30 scientists and amateur astronomers at observatories in New Zealand, Australia, South Africa, Argentina, Chile and Brazil – in addition to NASA’s orbital telescopes Hubble, Chandra and Swift.

Damineli monitored the event from the Pico dos Dias Observatory, operated by the LNA in Brazópolis (MG). He intends to monitor the next blackout from Chile with the help of the new equipment to be installed on the SOAR.