South Africa is making an important contribution to a Brazilian-led international radio astronomy project, known as the Bingo Telescope. Bingo stands for Baryon Acoustic Oscillations in Neutral Gas Observations. (To simplify, baryons are ‘heavy’ subatomic particles, of which the proton and neutron, found in atomic nucleii, are the best known.)

South Africa will be providing the data analysis software for Bingo, and the South African institution that is part of the international consortium developing, and which will operate the telescope, is the University of KwaZulu-Natal. Other countries participating in the consortium are China, France, Portugal, Switzerland, the UK and Uruguay. Funding is being provided by Brazil (from both federal and São Paulo state agencies), China, Switzerland and the UK, with the other members making contributions in kind. The main international partner is the UK, with four British universities involved.

Bingo will be unique, as it will be the first telescope designed to detect baryon acoustic oscillations (BAOs) using radio waves. BAOs are waves that were created in the early life of the universe by the interaction between protons and neutrons on the one hand, and radiation on the other. BAOs can be used, through a technique called intensity mapping, to measure the distribution of neutral hydrogen atoms across the universe. University of São Paulo (USP) Institute of Physics professor and project coordinator Elcio Abdalla explained in a USP article that it would be feasible to “investigate the shape and geometry of space, including its rate of expansion, if we know the apparent shape of BAO in outer space and, thus, study the dark energy. In technical terms, we will be measuring the cosmological parameters governing the geometry of the universe.”

Dark energy is the prime target of the project. On its website, the Bingo consortium points out that using BAOs “as a standard ruler allows us to measure the expansion of the universe as a function of redshift and, so, to constrain the properties of dark energy”. Dark energy is believed to make up 68% of the universe (dark matter contributes 27% and ‘normal’ matter less than 5%, but almost nothing is known about it. Bingo will help establish parameters for dark energy. It will also help study a phenomenon of still unknown origin, Fast Radio Bursts (high energy electromagnetic pulses which last only a few milliseconds), complementing a Canadian experiment.

The telescope will be composed of two fixed parabolic dishes: a primary one with a diameter of 40 m and a secondary dish with a diameter of 34 m. It will have an array of some 50 ‘horns’ (detectors), each one 4 m long, at the focal point. The radio waves will fall on the primary dish, be reflected onto the secondary dish, which will then both further reflect and focus them on to the detector array. The telescope will rely on the rotation of the Earth to scan a 10º strip of the sky.

The Bingo project was launched in 2016 and construction of the telescope is scheduled to start this year, with its commissioning intended to take place in 2022. It will be located in a remote part of Brazil’s Paraíba state, which lies in the north-east of the country, near the equator.

The location was chosen because it suffers from very low levels of radio frequency interference. The sparse cellular telephony infrastructure in the area is particularly important, as the frequencies in which the telescope will operate are very close to third-generation cellphone radio frequencies. The main issue is radio transmissions to and from aircraft flying international routes to and from Europe and North America. This is expected to be minimised by use of software; the most pessimistic estimate, the Brazilian news website UOL reported, is that aviation radio communications would result in the loss of one hour’s data a day.

Currently, there are no roads in the area. It is hoped that, in the initial stages, the Brazilian Army will provide vehicle logistical and maintenance support, although no agreement has yet been reached. Discussions are also being held with the Paraíba State Department of Streets and Roads, about the construction of access roads.