The first image of the Milky Way’s central black hole and the unique enhancement Africa could offer future tests of gravity

Abstract

Astronomers use a wide range of telescopes to study the universe, tuning into different parts of the electromagnetic spectrum to explore diverse astrophysical phenomena. Our eyes are sensitive to light that has a wavelength of approximately 500 nanometres. This is the region in which traditional, so-called ‘optical’ astronomy is carried out with facilities such as the Southern African Large Telescope in Sutherland. The choice of wavelength and telescope depends on the physical properties of the astronomical source of interest, e.g. hot gas at billion-degree temperatures is best studied at shorter wavelengths like X-rays. The recently launched James Webb Space Telescope will revolutionise our view of the infrared universe with a sensitivity significantly surpassing that of the Hubble Space Telescope. Another critical aspect of a telescope is the sharpness with which it can make out small details in a distant object. In this Commentary, we discuss a global network of radio telescopes known as the Event Horizon Telescope (EHT), observing light with a wavelength of 1 millimetre (mm), synthesising a much larger, earth-sized virtual telescope to achieve the sharpest detail attainable in astronomy. The primary objective of the EHT is to make images of supermassive black holes, behemoths that lie at the centres of galaxies and possess masses that range from about a million to ten billion times the mass of our own Sun.